sybase pd vs erwin wp

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WHITE PAPER

www.sybase.com

Version 2.1

A Comprehensive Analysis ofSybasePowerDesigner16.0InformationArchitect

vs.CA ERwin Data Modeler r8.1Standard Edition


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INTRODUCTION

Data modeling is more than just database design, because data doesnt just exist in databases. Data does not

exist in isolation, it is created, managed and consumed by business processes, and those business processes are

implemented using a variety of applications and technologies. To truly understand and manage our data, and

the impact of changes to that data, we need to manage more than just models of data in databases. We need

support for different types of data models, and for managing the relationships between data and the rest of the

organization. When you need to manage a data center across the enterprise, integrating with a wider set of business

and technology activities is critical to success. For this reason, this review will use the InformationArchitect version

of Sybase PowerDesigner rather than their DataArchitect version. If all you need to do is create data models for

an individual database, it is recommended you seek the cheapest tool or one that suits your specific technical

deployment needs. However, when you are connecting data models to components of the broader architecture, I

encourage you to read on to understand how CA ERwin compares to PowerDesigner InformationArchitect.

In this review, I examine the capabilities provided by CA ERwin Data Modeler r8.1 Standard Edition, and Sybase

PowerDesigner 16.0 InformationArchitect, using the evaluation editions available on each companys web site.

The PowerDesigner evaluation software provides the full capabilities, including a repository. The CA ERwin Data

Modeler evaluation provides a limited set of capabilities the Standard edition, which does not include the

repository capability.

PRODUCT OVERVIEWS

Sybase PowerDesigner and CA ERwin Data Modeler are two of the market-leading data modeling tools available.

Both enable you to create different types of data models, and link those data models to each other. Both enable you

to reverse-engineer databases, to persist the design in a model, and generate changes to the database. Both tools

provide a drawing canvas, and a variety of editing facilities for use in expanding the detail of the model. They also

provide standard usability features such as undo/redo, and the ability to customize the style of your diagrams. They

both allow you to share the information held in your models via reports, though only one provides a web portal. They

both provide essential collaborative features such as a repository.

However, when you look more deeply into how these features are delivered, youll see that ERwin does not come

close to matching the breadth and depth of capability provided by PowerDesigner.

CA ERwin r8.1 Data Modeler

On their web site, CA describes ERwin Data Modeler as an industry-leading data modeling s olution that provides

a simple, visual interface to manage your complex data environment. Before the release of r7, the predecessor to

r8, ERwin focused completely on the development of tightly-coupled pairs of logical and physical data models. Each

ERwin file can contain one logical data model, one physical data model, or one of each. A file that appears to contain

two models actually contains a single model with two views, logical and physical. In r7, ERwin introduced the concept

of design layers, a simple mechanism that gives hope to those of us who believe that the world of the data modeler is

more complex than just matched pairs of logical and physical data models. Look at the next section to find out more

about design layers in ERwin.


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ERwin has several editions and additional components:

Data ModelerStandard Edition

Core data modeling tool, providing logical and physical data modeling capabilities

Data ModelerWorkgroup Edition

This combines the Data Modeler Standard Edition with a repository to support workgroupcollaboration and governance.

Metadata IntegrationWizard

An OEM feature built into ERwin, to convert to and from the formats used by other tools,including most of their major competitors (including PowerDesigner)

Data ModelerNavigator Edition

A read-only version of the Workgroup Edition

Separately licensed component

Data ModelerCommunity Edition

A free version of ERwin. The tool features are restricted, and the largest model it canmanage is one with 25 entities/tables.

Data ModelerValidator

Verifies the structural integrity of data models or SQL/DDL code.

Separately licensed component

In addition, CA can bundle ERwin Data Modeler with OEM products for extracting ERP metadata and for data

profiling. Both products are also available on the open market, and can integrate with other data modeling tools,

including PowerDesigner. To trial ERwin, just complete a form on the CA web site and the file will be downloaded.

The downloaded file is called ERwin.exe, so be careful if youve downloaded previous versions. The Model Validatorrequires another registration and a separate download.

The evaluation license is valid for 14 days from the date of installation. Once the evaluation license has expired,

the evaluation version reverts to the Data Modeler Community Edition. If you do need temporary read-only access to

models, I suggest you download the trial version of the Data Modeler Navigator Edition of ERwin, which will give you

access for 14 days.

When my evaluation license expired, a UK reseller provided me with a one month extension.

Sybase PowerDesigner 16.0

Sybase PowerDesigner is a single tool, combining several standard modeling techniques (full lifecycle data

modeling, data movement modeling, business process modeling, enterprise architecture, and UML). PowerDesigner

provides a single working environment, underpinned by a flexible architecture and their industry-renowned Link and

Sync capabilities, the key to the comprehensive impact analysis capabilities of PowerDesigner.Downloading and installing the evaluation version of PowerDesigner was simple, and I only had to register once

for all available components. If you want to avoid involving DBAs in creating and managing a repository database for

your evaluation, you can host the repository database locally, using a specially licensed (free) version of Sybase SQL

Anywhere. You can also install the PowerDesigner Web Portal locally, allowing you to quickly create a complete test

environment. Some organizations choose to continue using Sybase SQL Anywhere to host their production repository.

Once the evaluation license has expired, you may contact the Sybase sales department for extensions. You may also

register and download the f reely distributable PowerDesigner Viewer software, for read-only access to any of your

models on the file system and/or in the repository you built.

PowerDesigner is available in several editions, illustrated in Figure 1.

Data Architect/DM Core data modeling tool, providing logical and physical data modeling capabilities, and thededicated XML model

Data Architect/RE The core data modeling capabilities, plus the collaborative capabilities made possible by therepository, the web portal, and web-based authoring

InformationArchitect Extends Data Architect/RE to provide additional capabilities for managing informationarchitecture

Enterprise Architect Extends the InformationArchitect edition to provide additional capabilities for enterprisearchitects

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Figure 1.PowerDesigner editions

DATA MODELING ACTIVITIES

Overview

This section examines the support provided by each tool for the key activities involved in the creation and

management of a chain of data models. In a later section, I examine some of the key features a data modeling tool

must provide in order to make these activities efficient, effective and productive.

The chain of data models is illustrated in Figure 2, using a PowerDesigner Business Process Model. Each box in

Figure 2 represents a fundamental data modeling activity. The other icons represent inputs and outputs to and from

those activities, most of which are data models.

The overall flow of activities represents a top-down modeling approach, though I expect all data modeling tools

to provide bi-directional support for each flow, and possibly support flows I havent shown, such as generating a

Relational PDM directly from a Business Subject Area Model.

There are three types of data models in Figure 2:

Subject Area Model Represents a business need. It is a very broad view, containing only the basic and critical

concepts for a given scope. The Business Subject Area Model (BSAM) is a subject area model of a defined portion

of the business (not an application). There are other possible types of subject area models, but the modeling

principles are the same, so examining support for the BSAM will be sufficient.

Logical Data Model Represents a detailed business solution, capturing the business requirements without

complicating the model with implementation concerns such as software and hardware.

Physical Data Model Represents a detailed technical solution. It loses some of the exactness of the LDM, butthis loss usually comes with gains in performance and usability within a given hardware and software set.

In Figure 2, the notation identifies the type of PowerDesigner data model that would be created in

each case:

Conceptual Data Model

Logical Data Model

Physical Data Model


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Figure 2.Data modeling activities

ERwin and PowerDesigner both provide support for all of the activities shown in Figure 2. However the effort

required, the user experience, and the resulting impact analysis capabilities are dramatically different.


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SUMMARY MATRIX OF THE DATA MODELING ACTIVITIES DEPICTED IN FIGURE 1

Task/Product ERwin PowerDesigner

Creation of amulti-level data

architecture

One tool is used to create three levels ofdata models with ERwins Design Layer

Architecture. Though they are not specificallyclear, the steps you would take are:

Create the SAM as a logical model, whereyou just ignore unwanted features, such askeys and attributes (if you choose to)

Derive the logical model from the SAM,in a new file

Amend the LDM

Derive one or more PDMs from the LDM

See Managing the SAM-LDM Relationshipon page 7 for more.

One tool is used to create all three level ofdata model; each level is supported by a

separate and distinct purpose-designed typeof data model.

The steps you would follow are:

Create the SAM in the CDM

Generate the LDM from the CDM

Amend the LDM

Generate one or more PDMs from the LDM

Impact Analysis fora multi-level dataarchitecture

Impact Analysis is fragmented. Each derivedmodel has a reference to the model fromwhich it was derived, but this is the only

record of the derivation visible in ERwin.The where used information for an entityor table will not tell you anything aboutdependencies on other models. The realdependencies between model levels areinvisible to the modeler, though they mustbe recorded somewhere within the derivedmodel, as the synchronization processmatches renamed objects.

Impact and Lineage Analysis provides acontinuous trail, from SAM to LDM to PDM(s),which can be interrogated from any point, in

any direction. The where used informationfor a SAM entity, for example, will show thetrail of dependencies through the LDM andPDM(s), and any other associated models.Additionally, PowerDesigner provides afunction to create an updateable graphic(i.e. model) which depicts the Impact andLineage Analysis.

The dependencies between models canbe shown on a project diagram, an ImpactAnalysis Diagram and/or via the GenerationLinks function.

Types of Data Model

Based upon this overview of typical Data Modeling Activities, it is necessary to align and integrate business

analysis with technology implementations to fully model a complete system. Where data modeling is concerned, an

organization must create subject area models, logical data models and physical data models.

A Subject Area Model (SAM)is a set of symbols and text representing the key concepts and rules binding these

key concepts for a specific business or application scope (Hoberman, Data Modeling Made Simple, 2009). It is

commonly expressed in the form of an entity-relationship diagram; however it is purely data and relationships. It is

not relational a SAM does not require foreign-key constraints.

A SAM helps us to capture, understand, and analyze the business needs of an organization, business area or

application from a data perspective. It is completely devoid of implementation details (data storage structures) or

software constraints. A key component of a SAM may be a set of elementary business data element definitions, which

may or may not have any eventual existence as modeled objects. PowerDesigner provides support for data elements

in the form of data items in the Conceptual Data Model (CDM). ERwin does not provide any support for data elements.

See Support for Elementary Data Elements on page 24 for more on this subject.

One or more SAMs may be created prior to developing the Logical Data Model (LDM) for a new application. A SAM

might also be created for an existing system where the technology needs to be verified with the business.

PowerDesigners CDM is designed for creating a SAM; ERwin can only support the SAM by ignoring capabilities in a

logical model, by pretending that a LDM is in fact a SAM.

A Logical Data Model (LDM)extends the concepts described in a SAM, describing a potential solution. The modeler

must be able to generate a LDM from the SAM. At first glance, the LDM is quite similar to the CDM in terms of the

objects it contains. However, a SAM is allowed to contain unanswered questions, such as those represented by many-

to-many relationships these questions must be answered in a LDM. Entities must have primary and foreign keys,

and many-to-many relationships must be converted into entities.


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The Physical Data Model (PDM) would typically be generated from the LDM. This model will be used to design the

schema of the database that will be used for the system. Entities become tables, attributes become table columns

and the relationships will be implemented in the database-specific structures (referential integrity, stored procedures)

When creating or generating a PDM, the specific database is chosen (Oracle 11i, Sybase ASE 15, Microsoft SQL Server

2008, PostgreSQL 8, etc). The PDM is frequently used to generate the data definition language (DDL) that will

allow for database creation or modification. It may also be used to create or update database schemas via a direct

database connection.

Again, the LDM and the PDM appear similar, but they meet different needs, and differ in terms of the detail

provided. The LDM is used to explore domain concepts with the business stakeholders; the PDM is used to create

and maintain the database. Multiple PDMs can be generated from a single LDM this can be useful for database

migrations, the creation of production and development databases, or application migrations.

Both tools allow you to generate multiple PDMs from a single LDM, and maintain the links from LDM to PDM,

though there are limitations in ERwin that dont affect users of PowerDesigner, which you can read about in

Dependency Analysis on page 11.

Design Layers

A modeling tool should provide the ability to model at any level, with generation to the other model levels or types.

All artifacts should be linked to their corresponding objects in the other models (for example, the entity Customer in

the SAM should be linked to the Customer entity in the LDM, which is linked to the Customer table in the PDM). Al

linkages should be maintained in the modeling tool so that a proposed change in an object can be analyzed before it

is changed. It is essential that the linkages form a single unbroken chain.

The activities described s o far have all been based on top-down analysis and design. In reality, data modelers

often use a hybrid approach, combining both bottom-up and top-down, so the tool must be able to support the

generation of a SAM or LDM f rom a PDM, and the generation of a SAM from a LDM. Both tools have this capability,

but the support provided by PowerDesigner is superior, due to the explicit support for all three types of data model,

and the loose coupling of data models.

ERwin

Historically, ERwin users have worked with tightly-coupled logical and physical data models. In this environment,

changes in the logical model are automatically reflected in the PDM (and there can only be one PDM). ERwinsData Modeler r7 introduced the design layers functionality, which allows you to derive one model f rom another,

maintaining linked models in separate files for the first time. So you can derive a LDM from a LDM, and a PDM from

a LDM, creating the chain of models shown in Figure 2. You can also work upwards, deriving a LDM from a PDM. You

do have to be careful when synchronizing a model with the model it was derived from the default comparison

options dont include all the properties you may need to compare, such as attribute and column data types.

I did have an issue with the design layers feature in ERwin. My LDM includes two many-to-many relationships

that I hadnt resolved. When I created a new PDM, the many-to-many references were still present. ERwin allows

you to use a transformation to resolve many-to-many relationships, but only in the LDM. In my evaluation edition,

transformations werent available to me, though the help information indicated that they should be. To resolve the

relationship manually, I wanted to copy one of the existing entries, which I did by selecting the entity on the diagram,

and using standard copy & paste. The new entity was not allowed on the diagram, as it had the same name as the

original entity. A look at the browser confirmed this I had two entities called Phone. When I renamed the new

entity to Contact Phone, it appeared on the diagram. No damage done, but I didnt expect to be allowed to create

duplicate entities. If you dont like this default behavior, you can change it via the model naming options.

My original model had been imported from a PowerDesigner CDM, and I was eventually able to carry out

transformations once I had added a new entity or relationship to the model. I raised this with the product team at CA,

who were able to import the PowerDesigner model without these restrictions.

The physical limitations of the storage structures would typically be included in the PDM, such as which tablespace,

the size of the tablespace, how many rows are anticipated, etc.


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PowerDesigner

PowerDesigner extends the two types of model provided by ERwin, to include a dedicated CDM, Object-oriented

models, and XML models. In addition, you can generate almost any type of model from almost anything else. Figure 3

shows the generation links available for data models. You can see the flexibility this gives you, with a model designed

to manage a SAM, and three different types of model to support physical data modeling.

Figure 3.Generation, import and export options for data models

When generating a new model, you can be selective about which objects to generate from in the original model.

A detailed record is kept of the links between models, and between objects in those models. This information is

available for carrying out impact analysis, and is also us ed to ensure that models stay synchronized, where necessary.

Sybase refers to these capabilities as Link and Sync.

Summary

ERwin provides great support for tightly-coupled logical and physical data models, and merging models together

(via the sync facility), but it cannot compete with the additional model types provided by PowerDesigner, nor with

PowerDesigners link and sync technology.

Managing the SAM-LDM Relationship

I used a realistic scenario to examine the support for integration of the SAM and LDM in each product using an

existing LDM to form the basis for a new SAM. The CDM was then amended, by hiding or removing the foreign key

attributes, and drawing a many-to-many relationship. I would then attempt to document business rules and stewards,

and link them to the entities in my SAM.How well does each tool support the SAM and links from the SAM to the LDM?

ERwin

Creating the SAM was easy to achieve, by deriving a new LDM from the original LDM. The next task is to make the

new model look more like a real SAM. The many-to-many relationship was not a problem, ERwin allowed me to draw

it OK. Hiding foreign keys, though? Not poss ible. Removing foreign keys? OK, I can do that, but only by removing all

attributes from the primary keys, and creating unique alternate keys for any candidate key attributes I want to keep.

I cant remove the primary keys or convert them to alternate keys, so I have to keep them.


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In step 2, create a list report containing relationship joins, making sure to include the child attribute properties in

the content. Again, select all the entries, and amend the value of child attribute to None, as shown in Figure 6. All

your migrated attributes will be removed from the model.

Figure 6.PowerDesigner Relationship Joins

In PowerDesigner, business rules can be defined in any model, or shared via the glossary which is held in the

repository. You can then link them to any object you want to.

In PowerDesigner, most dependencies between objects are pre-defined and named. Any additional links you create

are called Traceability Links, and you can assign a user-defined link type to each link. These link types can be presented

separately in an objects properties, filtered in lists of dependencies, and also displayed in dependency matrices.

In PowerDesigner, a steward would be represented by an organization unit in the business process model. There is

not a direct link from an organization unit to an entity, but creating one is a trivial task.

Figure 7.PowerDesigner entity with two new properties

Figure 7 shows an entity symbol, displaying two new properties that I added to the entity. One property is called

Steward, and links the entity to the organization unit called CRM Department in a process model. Populating this

property automatically creates a dependency between the two models, which can be shown on a project diagram, and

interrogated via impact and lineage analysis. The Steward property can also be displayed in dependency matrices (see

Dependency Matrices on page 55).

It is not possible to enhance models this way in ERwin.

Summary

ERwin allows you to create a SAM based on a LDM, but the new SAM is still a LDM at heart, pretending to be a

SAM. This pretense relies on ignoring standard LDM features, some of which (such as primary identifiers) cannot be

removed. The linkages between the SAM and LDM can be maintained via the Design Layers options, but full visibility

of those linkages is not available.

PowerDesigner provides a dedicated Conceptual Data Model, perfect for a SAM. When this model is generated from

a SAM, individual LDM objects are linked to their corresponding objects in the CDM. These links are visible from within

both models. The models can be synchronized in either direction using the standard model generation feature.

See also Dependency Analysis on page 11.


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Forward and Reverse Engineering

The PDM can be used to generate a database creation script or can be used to directly create the database through

an ODBC, JDBC and/or direct connection to the database server. This is known as forward engineering. Generating

a PDM from the structure of a database schema or DDL file is called reverse engineering; this may also be used to

describe the generation of a SAM or LDM from a PDM.

Every data modeling tool needs to provide reverse and forward engineering. Many organizations find it useful to

reverse engineer an existing system, generating a LDM and SAM f rom the PDM, so they gain a better understanding o

the database and the applications that use it.

Both tools examined here support forward engineering, see Database Support on page 18.

ERwin

ERwin supports reverse engineering from either a database or a script file. When reverse engineering, the newly

created model can be either a physical model or a logical/physical model (in accordance with ERwin terminology

the logical/physical model is actually a single saved file that has diagrams for both logical and physical models).

Template selection is provided and the process is wizard-driven. ERwin can attempt to infer keys (primary and foreign)

based on the schema of the incoming database.

PowerDesigner

PowerDesigner supports reverse engineering from either a database or a script file. Live database connection is

through an ODBC/JDBC connection with all objects supported. Script file reverse engineering is fully supported as

well. Object inference is supported if chosen through the reverse engineering options. As with all data model creation

modes, templates are supported for the reverse engineering. When reverse engineering from a live database, the

database statistics can also be included (i.e., number of distinct values in a column, average length of a character

field). Additionally, the statistics can be reverse engineered into a model without changing any of the objects. Reverse

engineering is wizard driven.

If a LDM is also required, this can be generated from the new PDM.

Summary

There is little to choose between the products here; your choice of tool may be driven by the DBMS versions you

need to support see Database Support on page 18.

Round-trip Engineering

The tool must also allow the modeler to reverse-engineer a database schema into a PDM, amend the PDM, and

then update the database from the PDM. This is known as round-trip engineering.

A data modeling tool MUST support both round-trip engineering and the hybrid approach described earlier.

Whether a modeler is s tarting from a conceptual model or reverse engineering a database into a physical model, a too

is useless unless it can support all aspects. Other features might be nice to have but this is baseline functionality.

Summary

Of the tools considered for this paper, only PowerDesigner provides full support for round-trip engineering as well

as giving the modeler the ability to work forwards or backwards (e.g., start from LDM, create CDM and PDM from the

LDM), and provide comprehensive analysis of the dependencies between all the models in the chain. PowerDesigner

has conceptual, logical and physical data modeling all in one tool. With all data modeling aspects in one tool, coupledwith PowerDesigners link and sync technology, the organization has the utmost flexibility in building, analyzing, and

maintaining data-oriented systems.

Integrating Data Models with Requirements and Processes

When a data modeler receives requirements or specifications from a business unit, the first step is to create

a subject area model (SAM). In many cases, there are also defined business rules, requirements documents, and

business process models. Ideally, the SAM should be tied to the process model so that the stakeholders within the

organization would have an understanding of the data and its use to support the processes. This also ensures that

data elements used in a system are necessary. There are many existing sys tems and applications that carry data that

is never used. The entities in the SAM can also be linked to the associated business rules, and requirements imported

from documentation.


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ERwin

ERwin Data Modeler does not support process modeling or business rules. There used to be a separate tool called

ERwin Process Modeler, which was capable of synchronizing subject areas, entities and attributes with ERwin data

models, but that product has been discontinued.

PowerDesignerIn PowerDesigner, the modeler is able to associate the subject area model with any process model that they have

access to. They can also link to any business rule in any model (not just data or process models) that they have access

to. Via the glossary feature, they can also associate the subject area model with globally-shared business rules.

Finally, requirements can be imported into a Requirements model from standard office documentation, and these

requirements can be associated with any modeling artifact.

Summary

PowerDesigner is the clear winner here; the definition of requirements and business rules allows the modeler to

document far more than just what goes in a database.

Generating Object-oriented Models

After the SAM has been created, the next step would be to generate an appropriate model to begin development.

Within the scope of this paper, that model would be a logical data model (relational). It may be useful to create anobject-oriented model from the SAM (PowerDesigner Enterprise Architect does this) but that is beyond the scope of

this paper.

Dependency Analysis

The very act of creating a data model creates dependencies between objects in that model, most of which will

be supported by the standard data modeling techniques, such as placing related attributes in the s ame entity,

and creating relationships. When a new data model is generated or reverse-engineered from an existing data

model, further dependencies are created. In addition, a data modeler may wish to create their own dependencies,

such as linking data modeling objects to requirements, business rules or business processes, or even to other data

model objects.

It is essential for a data modeling tool to allow the modeler (and others) to interrogate these dependencies this

may be called impact analysis, where used, or impact and lineage analysis. In the section below, I refer to this asModel Lineage.

In addition, there are dependencies between real-world applications, representing the movement of data between

those applications. In the section below, I refer to this as Data Lineage.

Model Lineage

At each step of the process, it is paramount for the data modeling tool to be able to show the lineage of the objects

in models. When examining the properties of a column in a table (in the PDM), the modeler should be able to see

what attribute of what entity was used for its creation. The modeler should also be able to trace back to the reason

the attribute was created, which may be to s upport a business rule, to meet a given requirement, or to implement a

given data element.

This visibility and traceability helps to ensure that the organization uses only the data elements necessary for the

implementation of a project or system. Furthermore, the understanding of where objects originate contributes to the

proper business process implementation. The corollary to this full traceability is impact analysis.

Impact Analysis

Impact analysis, or the ability to understand the consequences of a model change, needs to be a function of the

modeling tool. As part of the impact analysis, a modeler needs to be able to understand the objects model lineage).

Impact analysis includes more than just understanding where an object is used. It is also important to understand

what happened to an object after it was generated. Was an attribute in a SAM generated into the LDM? Was it then

generated into a PDM? Was the data type changed by the DBA when working on that PDM? Did a modeler generate

a set of classes from the LDM so that the developers would be able to start building applications? It is useful to be

able to store these analyses for later review as well as create version documentation. It is a better use of resources to

intelligently discuss the proposed change with the stakeholders rather than make a change in the LDM, propagate it

to the PDM and database only to find that the application now fails.


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The concept of impact analysis goes further when considering stored procedures or triggers that might have beencreated. If a modeler needs to change a data type or entity in the LDM, for example, an impact analysis would show if

the object is being used in a stored procedure. With a proper modeling solution and discipline, the modeler would be

able to have a discussion with the DBA prior to making the change.

ERwinERwin supports logical and physical data modeling, and allows you to pretend that a logical data model is a

conceptual data model, or SAM. Assuming you use the Design Layers model derivation process, the impact analysis

available is minimal, limited to saving the results of synchronizing two models. It is not possible to trace the lineage o

an object back from the PDM to the SAM, for example. You can use the standard complete compare feature to assess

the links between models related by derivation, but you will not meet with much success due to the fact that you

expect the SAM and LDM to be different. Merely renaming an entity in one of the models will fool complete compare

into concluding that they are different entities.

ERwin has a where used function that will show exactly where an entity or attribute in the LDM is used in the

PDM, if the PDM is in the same file as the LDM. Figure 8 shows the where used tab for the LDM entity in ERwin; this

tells you that the entity is linked to one relationship in the LDM, and that it appears on one diagram in the LDM. There

is no information about the SAM from which this was derived, or the PDM that was derived from the LDM. One of the

buttons on the toolbar under where used allows you to edit the selected related object.

Figure 8.ERwin Entity Editor where used

In ERwin, you can only see dependencies within and between logical and physical data models, and they are only

visible in the model in which they are defined.

PowerDesigner

In PowerDesigner, one tool provides support for all types of model. Any user can read any model (subject to

repository permissions/licensed package), and carry out full impact analysis in the tool, directly against the repository

and/or via the PowerDesigner Portal.

PowerDesigner has true and extensive impact analysis. An objects lineage is stored with the object. When models

and documents are stored in the repository, the impact analysis becomes more extensive. While viewing an objects

properties, clicking the Impact and Lineage Analysis button will bring up a window similar to the one in Figure

10. The analysis results depend on the analysis rule sets you use. Rules sets allow you to tailor the impact analysis,

determining the types of objects that are traversed in the impact analysis, and the properties that are displayed.

There are several rule sets supplied, and you can create your own if you need them, and share them via the repository.

Not only is the impact analysis available for the data modeling functionality, but it is core to the tool, and is

available throughout all modeling modules.


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PowerDesigner separates the concepts of lineage and impact to refer to the predecessors and successors of an

object. Putting it simply, Lineage refers to where the object came from, how it is defined, and Impact refers to where

it is used, those objects that will be affected if the object was changed or deleted.

For example, Figure 9 shows a chain of three data models. If we were to run Impact and Lineage analysis for

the Sample LDM, links to the BSAM would be regarded as Lineage, and links to Sample PDM would be regarded

as Impact.

Figure 9.Lineage vs. impact

By default, impact and lineage analysis only examines local models that are open, which could limit the scope of the

analysis more than you would like. Just select the Use Repository option, and PowerDesigner will extend the analysis

into the repository. Figure 10 shows the impact and lineage analysis for the same City entity shown in Figure 8. Note

the wealth of additional information shown, and the inclusion of links to requirements, business rules, and classes.

Entries with the s mall database symbol on their icon were retrieved from the repository.

Figure 10.PowerDesigner impact and lineage analysis

Each of the entries provides a shortcut to the actual definition in a local model, and to a summary of the

information held in the repository.


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PowerDesigner stores lineage and impact analysis information at both ends of the relationship, which enables you

to see dependencies from your model to other models that youve never seen before. For example, the LDM stores

details of generated tables, and the PDM stores details of the entities that tables were generated from.

Impact Analysis Model

The best way to fully appreciate the depth and breadth of the impact analysis capabilities of PowerDesigner is togenerate an impact analysis diagram. Did you notice the Generate Diagram button in Figure 10? If you click on that

button, PowerDesigner will generate a diagram illustrating the results of the analysis. The diagram can be saved,

providing point-in-time snapshots through the development life cycle. Remember, you can choose between different

analysis rule sets, which will produce different results and therefore different diagrams.

Figure 11 shows such a diagram, generated using the conceptual impact analysis rule set and no lineage rules

this results in a smaller set of affected objects. The left-hand entry is the City entity. The style of a symbol indicates

the type of model that it comes from. Double-clicking a symbol will open the properties of that object.

Figure 11.PowerDesigner impact and lineage analysis diagram

Figure 12.PowerDesigner impact analysis model in browser

Look at Figure 12. It shows the entries in the browser for the Impact Analysis shown in Figure 3. This information can

be saved as a model. If you have more than one Impact Analysis Model, you can compare them to see how the impact

has changed over time.

Summary

Where you have tightly-coupled logical and physical data models in a single file, ERwins where used capability is

up to the job. For any other circumstances, PowerDesigners impact and lineage analysis capabilities are far superior.


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Data Lineage

Managing the real-world movement of data between applications is an essential part of information management

in any organization. Knowledge of these data movements is probably documented in a variety of locations, such as

ETL tools, web services registries, JCL jobs, and spreadsheets. In data modeling tools, this Data Lineage can be linked to

physical data models, enabling anyone to trace the path taken by data through the organization.

ERwin

ERwin provides a facility for documenting simple data movements. You can create a data source in your PDM,

and populate it with tables imported from another model or SQL file. The columns in the imported tables can be

linked to columns in your PDM, and you can add comments to describe the data movement, perhaps describing the

selection logic.

There is no visual representation of the data source in ERwin; the link from the source tables to the PDM columns is

only visible in the PDM column data source tab, shown in Figure 13.

Figure 13.ERwin data source

PowerDesigner

In PowerDesigner, this mapping process is much simpler. Just fire up the mapping editor, specify a name for the

data source, choose a model to map to, make sure that the option to create default mappings is selected, and then

click on . Default mappings are created by matching object names and codes in the two models.

In Figure 14, I chose to map from my sample PDM to a PDM that I created by reverse-engineering the MS Access

Northwind database. I have added some mappings between columns by dragging from left to right. The Mappings

window in Figure 14 shows the details of the mapping from the Person table to the Customers table; using the tabs,

I can edit information about the mapping, such as the join criteria. All of the information shown in Figure 14 will be

available through impact and lineage analysis and dependency matrices.


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Figure 14.PowerDesigner mapping editor

In addition, PowerDesigner provides a dedicated model for data movements, which can import simple PDM-PDM

mappings. The Data Movement Model is designed to manage data replication using Sybase Replication Server, but it

can be used to document other data movements as well.

Summary

ERwin is great for capturing the context of an individual model, but it cannot compare with PowerDesigners

Mapping Editor or Data Movement Model. ERwins mappings are text-based, not graphical, and invisible from the

perspective of the related model(s). In PowerDesigner, any mappings created can be viewed in the mapping editor,

impact and lineage analysis, and via dependency matrices. They are treated in the same way as any other dependency

between objects they are visible and navigable.

Model Comparisons and Merges

Whether a model is in a repository, the current workspace or saved in the file system, it will be necessary to

compare models and merge differences from one model to another. The modeler might be working on a particular

entity in the LDM while another modeler would be working on the same model. Merge and compare functions help to

contribute to the ability for an organization to perform collaborative modeling. All tools examined for this white pape

contain merge and compare functions. The comparison operation is simply a visual representation of the difference

between models. The merge function should allow a modeler to accept or reject any or all changes.


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ERwin

ERwin has a Complete Compare function. It will work with open models in the tool, script files and models, or

databases and models. Complete Compare is wizard-driven and allows the modeler to choose the left and right

models. I like to be able to decide which model goes where, rather than leaving it up to the tool to decide. I would

always have the higher level model on the left; for example, a SAM on the left, and a LDM on the right . Once all

selections are made in the wizard, the resolve differences dialog box is displayed, allowing you to decide which

changes to apply, and in which direction. The merge is bi-directional.

You can mark known differences to be ignored, save them for later, and apply them to future comparisons.

The design layers feature also allows you to merge models in a limited fashion. You can add one or more model

sources, and choose the objects you want to copy across from those source models. Later, you can sync the target

model with any of the source models; differences between the two models are presented in the same dialogue as

used in Complete Compare. You do have to remember to save your sync options in a settings file, so you can use the

same criteria each time you sync the models.

PowerDesigner

There are two techniques you can use to merge content between two models in PowerDesigner. You can use

the merge model feature, which allows you to merge two model of the same type. Alternatively, you can choose

to generate from the source to the target model in update mode, which gives the option of saving dependenciesbetween the two models. Both of these features use comparison and merging functionality. It is part of the core

function set of PowerDesigner and not specific to data modeling. This model merge function is invoked automatically

(or can be invoked manually) when a model is s aved to the repository, copied into the workspace where a model is

already open, and when model generation is used to update an existing model.

PowerDesigners model merge provides fine levels of granularity and control as to what can be changed. Like ERwin,

PowerDesigner allows you to manually match source and target objects in the comparison. In PowerDesigner, you

can only merge models in one direction, from source to target. Uniquely, the PowerDesigner Portal provides the same

comparison features as the client.

A feature unique to PowerDesigner is the ability to copy objects from one model, and paste them into another

model as shortcuts to the original objects, or as managed replicas of those objects.

Summary

As you would expect in two long-established products, the comparing and merging facilities are comprehensive.

Both tools have a single merge-compare operation, which can be invoked in several ways. They both allow you to

choose the comparison criteria, filter the results, and save your selections for future use. Both tools allow you to

document the comparison by generating a report.

ERwin has the edge in two respects, as they allow you to mark and save known differences, and the merge is

bi-directional. PowerDesigner has the edge in its ability to generate and update more types of data model.

Update Flows

The boxes in Figure 15 represent the major components in an enterprise-level data modeling environment these

are all supported by both products. Each dashed line in Figure 29 represents a possible flow of updates to models,

either from modelers (experts in data modeling) or from Reviewers (who arent experts in data modeling). Again, all

these update flows are supported by both products.

Figure 15.Update flows


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In both tools, a standalone edition is available that only supports the data model component, and therefore only

supports update access by modelers. In ERwin, that support is limited to logical and physical data models, and

pretend subject area models. PowerDesigner is available in several standalone editions, the most basic of which

supports logical and physical data models, XML models, requirements models, impact analysis models, and free

models, which provide a simple means of creating non-specific drawings and models. Conceptual and data movemen

models are available in the InformationArchitect edition.

The standalone editions may be sufficient for small organizations, but the majority would require an enterprise

or repository edition. ERwin workgroup edition includes the repository. The PowerDesigner RE editions allow access

to the repository and web portal. The PowerDesigner web portal allows nominated users to input updates to text

properties, such as entity definitions. These updates will be reviewed later by the model owners.

REQUIRED FEATURES FOR A DATA MODELING TOOL

This section examines some of the key features a data modeling tool must provide in order to perform the activities

described earlier, in an efficient, effective and productive manner. The features are grouped into the following

categories: Core Modeling, Collaboration, Interfaces & Integration, and Usability.

Core Modeling

Database Support

Since one of the goals of using a modeling tool is to create, modify, understand and analyze databases, it is

necessary that the tool support a variety of DBMSes. Even more important is the ability for the user community to add

additional database support without waiting for the vendor to provide an upgrade. This might be necessary when a

system needs to be migrated from an older database to a more current solution, so the user can reverse-engineer the

old database, generate and modify LDMs and SAMs, modify models, then create a new database. Consider a modeling

tool that provides database definition files in an XML format so that additional database definition files can be

created by the user.

To make this degree of customization possible, an intelligently designed modeling tool will be engineered so that

the core executable reads definition files. The executable file is extensible, not only for different modeling modules

(CDM, LDM, PDM, XML) but for database definition files. With a tool designed thusly, supported database updates can

be released as soon as the database vendor makes the specifications available. The entire modeling tool does not haveto be upgraded. Furthermore, with separate core and external definition files, it is pos sible for the customer to add

support for a database not supported by the tool vendor.

PowerDesigner supports this paradigm while ERwin does not. PowerDesigner uses a single executable that

is extended through DLLs for modules and XML definition files for all databases. Because of PowerDesigners

architecture, it is possible to add support for a specific database system even if Sybase does not upgrade

PowerDesigner to support it. The database definition files are stored in the file system as XML files and can be

modified. ERwin does not provide this ability.

The following table summarizes the DBMS support provided by each tool. A , between version numbers indicates

that different database definitions are used for the DBMS versions. If the separator is -, that indicates that a group

of versions is managed by the same database definition. The - means that version-specific database support is not

provided: a common set of attributes is supported.


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DATABASE POWERDESIGNER 16 ERWIN R8.1

Adabas D Yes No

Allbase/SQL G.1 Yes No

ANSI Level 2 Yes No

Hitachi HiRDB No NoHP Neoview R2.4 No

IBM DB2 for AS/400 Yes No

IBM DB2 for z/OS formerly OS/390) 6.x, 7.x, 8.x, 9.x, 10x 8.1, 9.1

IBM DB2 for Common Server (aka LUW) 6.x, 7.x, 8.x, 9.0, 9.5, 9.7 9.1, 9.5, 9.7

IBM DB2 for i No 5.x/6.x

Informix SQL 8.x, 9.x, 10.x, 11.x 9.x/10.x/11.x

Ingres 3.0.1 2.5, 2.6, 2006

InterBase 5.x 5.x, 6.x 5.x

Microsoft Access 2000, 2007, 2010 2000, 2002, 2003

Microsoft SQL Server 2000, 2005, 2008, 2008 R2 2000, 2005, 2008

Microsoft Visual FoxPro No YesMySQL 4.0, 5.0 5.x

Netezza 4.5, 5.0 No

NonStop SQL Yes No

ODBC 3 2.0, 3.0

Oracle 8i2, 9i, 9i2, 10g, 10gR2, 11 10.x/11.x

PostgreSQL 7.3, 8 No

Progress No 9.x/10.x

Red Brick Warehouse 6.2 5.x

SAS No Yes

Sybase SQL Anywhere (previouslyWatcom SQL or Sybase ASA)

9, 10, 11, 12 No

Sybase AS Enterprise 12.0, 12.5, 12.5.1, 12.5.2, 12.5.3a, 15.0, 15.0.2, 15.5 12.5/15

Sybase AS IQ 12.5, 12.6, 12.7, 15.0-15.1,15.2 12.x

Sybase Avaki Yes No

Teradata V2R5, V2R6 2.6, 12, 13

Both PowerDesigner and ERwin include support for all the database platforms listed above in every edition of

the product.

When considering the database support that a tool offers, it is not enough to say that a particular database system

is supported. For example, PowerDesigner supports all of the Oracle data types and nuances (storage, partitions) that

are in Oracle 11g, including over 80 data types. ERwin supports fewer than 30 of the Oracle data types. If this is the

level of support for a popular database (i.e., Oracle 11g), what might the support be for a less popular database?


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Figure 16.Oracle data types in PowerDesigner

Figure 17.Oracle data types in ERwin

As another example of the support offered by PowerDesigner for Oracle 11g, see the following figure.


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Figure 18.Oracle physical options in PowerDesigner

PowerDesigner has all physical options on one tab. All Oracle 11g partition options are supported, as well as column

properties, physical properties and all other options.

ERwin doesnt present all the properties of an object in one dialogue. For example, Figure 19 shows the seven

different dialogues available for tables. If the properties you need to read are not in the dialogue you have open, you

must close it and open another (you can only have one open at a time).


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Figure 19.ERwin Table menu

ERwin separates physical options from partitioning. There is no support for reference or system partition types.

Figure 20.Oracle partitioning schemes in ERwin

Summary

There is no doubt that the database support provided by ERwin meets the requirements of many data modelers.

The product probably supports the majority of features for the majority of DBMS versions in use. If your requirements

stretch beyond the majority in either respect, PowerDesigner is the product for you.

Modeling Notation

There are several different modeling notations commonly in use. A modeling tool should support more than

one notation.

Information Engineering a standard notation in use in many tools, though there are several variations.

Generally, the entities and tables are represented by rectangles and the relationships are represented by lines with

different endpoints, usually the popular crows feet.

Barker created by Richard Barker and popularized by Oracles CASE tools, Barker notation displays inheritancesinside the parent entity symbol, has its own multiplicity notation and attribute ornaments. Relationships are

drawn in two parts with each reflecting the multiplicity of the associated entity role.

IDEF1X in this notation, each set of relationship symbols describes a combination of the optionality and

cardinality of the entity next to it.

Entity/Relationship Sybase specific, Entity/Relationship is an implementation of IE notation.

Merise developed as part of the Merise methodology, it uses complex multi-entity associations instead of

relationships.

E/R + Merise both entity/relationship and Merise are used in the same model.


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NOTATION POWERDESIGNER ERWIN

Information Engineering (IE)

Yes

(called Entity/Relationship) Yes

Barker Yes No

IDEF1X Yes YesMerise Yes No

IE + Merise Yes No

Summary

Both products support two of the most commonly used notations, IE and IDEF1X, though there are differences in

the IE notation ERwin uses dashed and solid lines to indicate whether or not a relationship is identifying, whereas

PowerDesigner uses a triangular dependency symbol. If you want to use the Barker notation, or your organization uses

the Merise methodology, PowerDesigner is your only choice.

Business Glossary

Many development projects and business re-engineering programs develop a glossary of terms, usually as a

spreadsheet. These terms may even form part of the naming standards for data models, but the majority of tools, such

as ERwin, provide no support for this activity beyond the ability to record pairs of words to be used when translatingbetween logical and physical names for data.

PowerDesigner provides support for a taxonomy of business terms via the repository-based Glossary. In

environments with a repository, administrators can deploy a glossary of Terms: a Term is a word or phrase that forms

part of a controlled vocabulary. In the Naming Conventions section of Model Options, you can enable the use of

the Glossary for auto-completion of names in any model. This also enables you to check the names of objects for

compliance with the Terms in the glossary as part of the standard check model feature.

If you enable the Glossary in a model, Terms are suggested from the Glossary as you type the name of an Object.

If you type a recognized synonym for a Term, then PowerDesigner suggests you use the Term instead.

When you reference a term in the name of an object, PowerDesigner automatically adds that object to the list of

objects that reference the term. This cross-reference is available in dependency matrices and impact analysis.

Summary

ERwin does not support anything equivalent to the PowerDesigner Glossary. PowerDesigner is the only mainstream

data modeling tool to offer a shared, linked, glossary of terms.

XML is Special

A physical data model describes data persisted in a database. In many cases, that data was transmitted to the

application that populated the database as an XML document or message. The structure and content of that

document or message is a key component of the organizations data integration, and must be included in impact

analysis and data lineage capabilities. An enterprise data modeling tool should be able to create an XML-specific

physical data model, in which the modeler can design the structure of one or more XML Schemas, and then generate

XML schema files. The tool should also be able to import an existing XML Schema into a dedicated XML model, from

which future versions of the schema can be generated. Only PowerDesigner has all this XML capability. ERwin can

generate and reverse-engineer XML Schema, but it relies on a relational model to do so. The translation between a

relational PDM and the essentially hierarchical nature of XML makes it difficult to effectively manage the development

of XML Schemas in ERwin. The lack of a model dedicated to XML, with XML-specific objects, means that it is impossible

to provide full, accurate impact analysis for XML schemas in ERwin.

Summary

ERwin does not provide an XML-specific data model. PowerDesigner is the only mainstream data modeling tool to

offer a dedicated XML model.

Denormalization of physical data models

It is vital for any data modeling tool to provide automated support for denormalization of physical data models,

including rollback capabilities.


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ERwin

ERwin supports rollups, rolldowns, horizontal and vertical splits, and column denormalization. Rolling up subtypes

into the supertype, and rolling down supertypes into subtypes, are supported by specific transformations.

The Transforms toolbar provides access to the different types of transformations available, and also allows you

to display the objects before or after transformation. You can also reverse or resolve all transforms resolving a

transformation deletes the original objects.

PowerDesigner

PowerDesigner supports table collapsing (rollup and rolldown), horizontal and vertical partitioning, and column

denormalization. You have the option to retain or delete the original tables. All transformations (except column

denormalization) are recorded as transformation objects, linked to the newly-created objects. Via the model menu, you

have access to a list of transformations.

Rollup and rolldown are supported by collapsing tables into a new table you have the option to keep or remove

the original tables. Rolling up and down super and sub types is best carried out in the LDM, using the options that

govern the generation of supertype and subtype tables.

A transformation can be rolled back if the original tables were generated from another model this does not

re-instate the original tables, so you would need to re-generate them if you didnt keep them when you carried out

the transformation. If you think you will need to rollback a transformation, I suggest you keep the original tables andreferences, and uncheck the Generate property to prevent them being generated into a database.

Column denormalization works by utilizing the standard replication feature it replicates columns across tables.

When the original column is updated, the replicas are also updated. The modeler has control over how strictly the

copies mimic the original column.

Summary

The tools both provide adequate support for denormalization. They take different approaches with respect to

managing the pre- and post- denormalization views of the model; if you are used to one approach, you need to be

aware of the differences if you change tools.

Support for Elementary Data Elements

Previously I introduced the concept of elementary business data elements, which may or may not have any eventua

existence as modeled objects.

PowerDesigner

PowerDesigner supports this via the concept of Data Items in the CDM. A Data Item is a conceptual data element

that exists independently of any model objects, such as Entities or Tables. Data Items are integral to the CDM, where

every attribute automatically references an underlying Data Item. They are not present in the Logical Data Model or

Physical Data Model.

ERwin

ERwin does not support elementary data elements.


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Other Core Features

CORE FEATURE POWERDESIGNER 16.0 ERWIN R8.1

Enforce naming standards based onbusiness vocabulary

Yes using terms in theglossary

No

Record the vocabulary of the business

as Terms

Yes No

Persist XML schemas as a model fortraceability and normalization

Dedicated XML Model, orUML class model

XSD import not supported by evaluationedition uses the same metadata bridgeas ER/Studio, so it will produce the sameresult, a relational model

Check Model (validation) Yes can customizechecks, and determinecriticality. Auto-fixavailable on some checks.Can access objects fromresults list without closingthe list

Separate product (Data Model Validator)that appears to be comprehensive. It canread and validate DDL and ERwin models

I was unable to launch the validatorfrom ERwin I was informed that

the DBMS in the model (Oracle 11g) isinvalid. I was also unable to open thesupplied sample eMovies ERwin model

Customizable Data Type mapping Yes defined within theproperties of the DBMS

Datatype Standards Editor allows you toedit logical-physical and physical-physicaldata type mappings. Can save multipleversions, and attach to models. I haventseen any reference to DBMS-specificmappings, but Im sure they must bemanaged somehow

Inter-Model Generation &Synchronization

Yes LDM-PDM

PDM-PDM via model sources

Managed re-use of modeling patternsand reference models within datamodels

PowerDesigner librarypushes reference modelsto all repository users

Partial via model templates at the time ofmodel creation

Multiple diagrams within a model Yes Yes

Naming standards (enforce/check) Yes using the glossary Partial

Provide business name toimplementation name translations

Yes Yes

Real-time updates of metadata Yes Yes

Replicate attributes between entities(ditto columns and tables)

Yes see above No

Replicate objects between models Yes No

Shortcuts to objects in other models Yes No

Subject areas (subsets) in a model Yes Only 1 level

Support for elementary data elements Data Items in the CDM No

Automated support fordenormalization of physical datamodels, including rollback capabilities

Yes Yes

Compare a data model with anexisting data artifact such as an XMLor database schema, update the modeland/or the data artifact as a result

Yes Yes databases only

Direct support for all model objectsspecific to a technology e.g. a specificRDBMS version

Yes No


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Core Feature POWERDESIGNER 16.0 ERWIN R8.1

Filter Dangling Relationships fromschema generation

Yes Yes

Generate data definition language(DDL) files

Yes Yes

Multidimensional modeling Yes No distinct notation Yes

Reverse engineer physical data modelsfrom data definition language (DDL)files or database connections

Yes Yes some via Meta Wizard

XML schema generation Yes Yes

XML-specific physical data model Yes No

Configurable support for technologyobjects (e.g. creating generationcapabilities for unsupported DBMS)

Yes No

Impact and lineage analysis betweenmodels

Yes Partial

Impact and lineage analysis

within a model

Yes Partial

Visual editing and display ofdata lineage

Yes No

Compare two data models, of the sameor different types, and update one orboth models as a result

One-way update Yes

Collaboration

Repository

If there is going to be more than one person who will need access to a model, then a repository is necessary. The

repository provides a common location to store documents, models, and other files. It should be able to store different

versions of models as well. From an administrative perspective, the repository provides the organization with a single

storehouse for backup purposes. With proper use, the repository would hold the most current version of a model so

that when a change needs to be enacted, there is no question as to where the proper model resides. Additionally, the

repository would eliminate the necessity to locate the individual who might have a model locked or who might have

implemented some changes.

A repository is necessary to support collaborative modeling, by managing versions of models. A database

administrator may need to implement a change in a physical model, but, at the same time, a modeler needs to

implement a change in the same model. Both people would be able to extract a copy of the model from the repository

make changes, and then put the model back into the repository. Upon storing the model back into the repository, the

differences should be presented to the modeler consolidating the changes.

Both products are available with a repository.

PowerDesigner

PowerDesigner implements full impact analysis through the repository, allowing you to trace dependencies through

models that you dont have available locally. With all the models in the repository, it is much easier for the tool to trac

all the objects and be able to report to the modeler.

The Model Merge functionality discussed above is presented each time a model is consolidated into the repository

The changes between the version in the repository and the model being checked in are highlighted with the option to

accept or reject any or all changes.

The repository presents in the tool browser as a folder-based structure. Security is implemented in the repository

users will have various permissions, based on roles. These permissions are defined by the repository administrator and

are typically different from the database user permissions. Branching and sub-branching, versions, locks, freezes are

all supported.


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The repository can be installed on a local Sybase SQL Anywhere database initially, avoiding the need to purchase

disc space and involve DBAs until youve proved what you need. It can then be migrated to one of several supported

database platforms.

ERwin

The repository for ERwin is the Model Manager, which provides the model management functionality for ERwinData Modeler Workgroup Edition.

Model Manager provides library management, allowing for folder creation and better organization within the

repository. Sub-models are supported, not only through ERwin but also in Model Manager. ERwin Model Manager is

more of a model store than PowerDesigners repository; it does not push any information out to users, unlike the

library feature in PowerDesigner; nor does it allow you to browse content using the client software or a web portal. CA

supports version management in the Model Manager, including locked versions, difference reports, and model rollback

to previous states. The Model Manager allows you to rollback to any point in the life of a model.

The repository is a database wherein the models are stored and managed. Users must check out models and check

them in again, as in a standard version control system. Archiving and versioning are performed within the repository

and the tools that are available to modelers are also available to work with models in the repository (e.g., Compare

and Merge, Subject Areas, ). Security is implemented in the repository; users would have roles and privileges.

Branching and sub-branching is supported.

CA suggests that you use the Model Manager in one of the following ways:

Model-DrivenDevelopment

Changes to the schema are made to the model first and then forward-engineered

System-DrivenModels

Changes are made directly to the schema and the schema is reverse-engineered into the modelto reflect the changes

InformationalModels

Contains logical-only models, enterprise-wide models, or standards and sample models

The choice you make will influence the way you set up the repository database and the supporting policies. I

havent had access to the Model Manager during this evaluation so I cant be sure of the implications of this choice. In

reality, you would probably want to use a repository in a hybrid fashion, combining all three approaches.

Summary

ERwins repository offering is essential for multi-user environments. It is useful as a way of managing access to

models, and versions of models. However, it does not provide any direct access to repository content for modelers or

non-modelers, unlike PowerDesigner, which allows modelers to browse the contents of models in the repository, and

incorporate the repository in searches. Via the Web Portal, non-modelers can browse and search the PowerDesigner

repository contents in the s ame way; and selected non-modelers can also (us ing the new Composer license) update

text properties directly in the repository.


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Web Portal

A repository is ess ential for effective collaboration between modelers, and a web portal is essential for effective

collaboration with non-modelers.

PowerDesigner

The PowerDesigner web portal allows non-modelers to browse, search and compare models in a s imilar way tousers of the desktop software. The search facilities are actually better than those available on the desktop, and the

impact analysis capabilities are comparable. Portal users have real-time access to the repository, so they know theyre

viewing the latest checked-in models. The new Composer license allows selected users to edit textual definitions via

the portal (assuming youve granted them access to the models, of course).

ERwin

ERwin does not provide a web portal.

Other Collaboration Features

COLLABORATION FEATURE POWERDESIGNER 16.0 ERWIN R8.1

Compare versions of repository based models Can compare any version of anymodel to any version of any modelof the same type

No

Manage configuration of different models thatcontribute to release

Yes No

Provide subscription for anyone to know whenmodels are checked-in

Yes No

Impact and lineage analysis via repository Yes No

Projects and frameworks matrices Yes No

Share and apply a house style for theappearance and content of data models

User profiles help you to standardizethe look and feel of your models andto support standards

Themes

Share reference models and common businessrules via a repository

Yes No

Direct access to models and links between

models via a portal, designed for use bynon-specialist users of data models

Yes No

Read-only access to models Viewer software is free Navigator edition list price c. $1,000

Search and impact analysis capabilities via aportal, designed for use by non-specialist usersof data models

Can search models, compare models,follow all traceability links anddependencies (impact analysis)

No

Web-based functionality at no additional costto the repository

Yes No

A shared location for the storage of andcontrol of access to data models

Repository Enterprise licenserequired

Repository workgrouplicense required

Control access to subsets of a model, perhapsindividual model objects

Yes down to packages withinmodels

Yes down to submodels

Integrate with LDAP/Active Directory for userauthentication Yes Yes

Resolve potentially conflicting changes madeby different analysts

Yes Yes

Role-based management of access torepository content

Yes Yes


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Interfaces & Integration

Import and Export

A modeling tool must allow the modeler to import and export content in various types of models and related

external files. Both import and export allow the tool to work with other tools or provide information to other people,

organizations, or solutions. It is useful for the tool to be able to work with metadata in a generic fashion, but specificimporting will provide greater overall support.

Both tools offer s everal import and export features.

ERwin

ERwin Data Architect includes an OEM Metadata Integration Wizard1, enabling users to export and import to and

from many other formats.

The ERwin Bulk Editor is a single window that allows you to edit a small set of properties over a large number of

objects. It also allows you to export to and import from CSV files.

PowerDesigner

PowerDesigner does not include the Metadata Integration Wizard, choosing instead to rely on several built-in

import engines. If you need additional metadata conversions, you can purchase additional metadata bridges from

companies such as Reischmann2

. They supply standard bridges, and can configure them quickly for you, if necessary.The inclusion of the Metadata Integration Wizard means that ERwin appears to have the more capable model

import capabilities of the two tools here. In reality though, the majority of data modeling tools can save models in

ERwin XML format, which PowerDesigner can import. In fact, it can import and several ERwin files at the same time,

and create any combination of conceptual, logical and physical data models from each ERwin file.

The support provided by PowerDesigner for the import and export of model content, such as entity descriptions

and comments, is far superior to anything in ERwin. PowerDesigner provides powerful, configurable facilities to export

to and import from Microsoft Excel, capable of creating complete models in one pass, including dependencies. No

programming is required, though an understanding of the underlying metamodel will help you import some of the

more complex metadata, such as dependencies.

Once defined, an Excel import can be re-run whenever you need to the import definition is an object in its own

right, accessible via the browser.

Summary

Using the OEM Metadata Integration Wizard, ERwin can transfer metadata to and from more tools and formats

than PowerDesigner. Realistically, this apparent advantage is not as great as it seems: the take-on of models in

different formats is often a one-off exercise, which can be facilitated by generating ERwin models from your existing

tool, and importing them into PowerDesigner. Longer-term import and export requirements can be managed by the

excellent bridges supplied by Reischmann.

The ERwin bulk editor allows you to do simple CSV-based import and export; this just cannot be compared to the

flexibility of PowerDesigners Excel export capability, available from any list of objects or sub-objects, or dependency

matrix. Nor is it comparable to the Excel Import Wizard available within PowerDesigner.

1See www.metaintegration.net/ for details of supported formats2See www.reischmann.com/ to find out more


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Other Integration Features

INTERFACES & INTEGRATION FEATURE POWERDESIGNER 16.0 ERWIN R8.1

Design-time change management Yes Yes

Dedicated data movement/ETL Model

Yes No

Document data movements Via the Mapping Editor orthe Data Movement Model(DMM). A DMM can convertPDM-PDM mappings intoa model

Partial

Generate scripts to manage themovement of data through thearchiving cycle, or data movements

Yes No

Generate test data Yes No

Build cross-references or traceabilitylinks between data model objectsand business requirement models

Yes No

Build cross-references or traceability

links between data model objectsand shared business rules

Yes No

Mapping Tool (connections betweenobjects in different models)

Yes No

Persistent Impact Analysis Model Yes No

Export data models in a format thatcan be imported into other tools

Partial Yes via Meta Wizard

Import existing data models createdby other tools

Partial Yes via Meta Wizard. Cannot importPowerDesigner LDM. May need to switchoff consistency check to import fromER/Studio v9.

Preview, print, and save modelcomparison results

Yes Yes

Usability

Property Editors

Both tools provide tabbed editors for editing object properties. As weve already seen, ERwin divides an objects

properties across several different sheets, whereas PowerDesigner supports all properties on a single sheet.

Furthermore, the PowerDesigner property sheets can be tailored.

One useful feature of the ERwin property sheet is the ability to choose another object of the same type to edit

without closing the sheet. Thats necessary though, as you cant edit more than one object at a time in ERwin. In

PowerDesigner, you have as many object property sheets open as you can handle.

I find the PowerDesigner editors to be clearer than those in ERwin. For example, contrast the PowerDesigner entity

and attribute editors shown in Figure 21, with the equivalent from ERwin in Figure 22.


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Figure 21.PowerDesigner entity and attribute editors


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Figure 22.ERwin attribute editor

Using the model extensions facility (see Extensibility and Customization on page 35), we can change the way in

which properties are presented in PowerDesigner; you could completely replace the standard tabs with your own.

Summary

The property editors in PowerDesigner are simpler and more flexible than those in ERwin, and you can open more

than one at a time. If you dont like them, you can change them. Only PowerDesigner allows you to change the way

in which properties are presented in the editors; you could completely replace the standard tabs with your own. See

Extensibility and Customization on page 35.

Grid-based Editing

Grid-based editing allows you to view and edit more than one object at a time, with each object occupying a row in

the grid.

PowerDesigner

PowerDesigner provides a grid-like editing mechanism, within the properties of a single object, such as the list

of attributes shown in Figure 21, and also within a list of objects or a List Report. You can customize the properties

displayed in the grid, and filter the objects or sub-objects listed. For example, Figure 23 shows a list of relationships

that has been customized to show information about the two entities that participate in the relationship. This grid

can be used to edit or create relationships, and the content can be exported to Excel. Once outside PowerDesigner, the

spreadsheet can be edited in Excel, and the results can be re-imported into PowerDesigner to update the model.


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Figure 23.List of relationships in PowerDesigner

The same capabilities are available when editing the attributes of an entity, or even all the attributes in the model.

In addition, PowerDesigner allows you to create permanent lists of objects, known as list reports. List reports are

stored in the model, and are always accessible from the browser. You can create many list reports for a type of object,

and can even save snapshots of the content. Using the snapshots, you can view the properties that used to have in the

past. You can open multiple concurrent object lists and object property sheets.

PowerDesigner object lists and lis t reports provide simple validation capabilities. For example, you can create a list

report that contains attributes, and only displays attributes that do not have a domain specified.

ERwin

ERwin provides a simple grid-based editor, called the Bulk Editor, which opens in a separate window. The bulk

editor only allows you to open one grid at a time. Each time you open the bulk editor, you need to run the bulk editor

wizard to choose the objects and properties to edit; to make life easier, you can save settings in external files.

Summary

ERwins Bulk Editor is a pale imitation of PowerDesigners grid-based editing capabilities. You can only edit one set

of objects at a time, whereas PowerDesigner allows you to open as many concurrent grids as you can handle; it also

remembers your customizations, so you dont have to save in a file and load them each time.

Diagram Style

Data model diagrams are designed to communicate information to an audience. For one audience, you may want to

highlight the entities relating to a given business area. For another audience, you may need to highlight entities that

have changed recently. Dont underestimate the part that diagram style can play in s uccessful communication. Were

not playing with content and color just because its fun.

ERwin

ERwin allows you to create and apply themes, covering default colors, line options and fonts for different object

types. Its a simple operation to apply a theme to a model, submodel or diagram, and to vary those s tyle components

for individual symbols. You can also determine the content of symbols on a submodel, and also for individual s ymbols,

using pre-defined sets of options, which can be tailored for individual diagrams. Figure 24 shows two tables with

different colors and content.


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Figure 24.Themes in ERwin

Applying a theme to one or more objects is really simple, using previews of the available themes to help you make

your choice. The theme is applied immediately.

PowerDesigner

In PowerDesigner, you have more control over the style and content of symbols. Defaults can be set, and shared

via user profiles. As in ERwin, each diagram has default styles and profiles, inherited from a user profile or another

diagram. Unlike ERwin, you cant pick from a list of available themes and have them applied immediately. However,

you can get the style of one symbol and apply it to other s ymbols, even symbols of a different type.

The real difference in PowerDesigner is that format and content can be varied from the defaults for each symbol,and the font can be varied for each sub-object. The layout of properties in symbols is also more flexible; the symbols

can be laid out with horizontal and vertical property groups, rather than just a single vertical list of properties. You can

also specify icons to display on object symbols in place of extended attribute values by creating an attribute icon set

with an icon for each possible value. If you want to hide a sub-object on a symbol (such as a hiding an attribute on an

entity symbol), you can.

Figure 25 shows a sample PowerDesigner diagram. Every entity is showing three new properties, Plural name,

Steward and Review Status. The value of Review Status is shown by the icon at the top of each entity symbol. The style

and content symbol for the Contact entity has been customized: fewer properties are shown for attributes, the entity

line and fill have been altered, and the font for one of the attributes (Web Address) has been altered to accentuate it.


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Figure 25.Colors, fonts and style in PowerDesigner

Summary

The Themes in ERwin make it easy to apply a custom style to symbols. Unfortunately, the style options end there.You can adjust the content of symbols, but only by model or sub-model. PowerDesigner does lack the ease of use of

ERwins themes; instead you can apply a user profile that changes the default symbol style. You can apply it to existing

objects if you want to, though its not as straightforward to do.

Where PowerDesigner really beats ERwin is the control you have over exactly which s ub-objects are displayed on a

symbol, and the style and content of individual symbols.

Extensibility and Customization

Working with a data modeling tool will require some adjustment of the modeler to the tool and some tool

modifications for the enterprise and the modeler. Extensibility and customization needs will vary with the type of

work being done as well as the needs of the organization. This section is concerned with the ability of the tool to

adjust to the needs of the environm

sybase pd vs erwin wp

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