topic2 databasearchitecture aug14

Database and Web Database Systems

CT014-3-2

Database Architecture

CT014-3-2 Database and Web Database Systems Database Architecture Slide 2 (of 44)

Topic and Structure of Lesson

•Purpose of three-level database architecture.

•Contents of external, conceptual, and internal levels.

•Purpose of external/conceptual and conceptual/internal

mappings.

•Meaning of logical and physical data independence.

•Distinction between DDL and DML.

•A classification of data models.


•Typical functions and services a DBMS should provide.

•Software components of a DBMS.

•Meaning of client–server architecture and advantages of this

type of architecture for a DBMS.

•Function and importance of the system catalogue.

Topic and Structure of Lesson (2)


Learning Outcomes

At the end of this lesson, YOU should be able to:

•explain the purpose of three-level database architecture.•explain the meaning of client–server architecture and advantages of this type of architecture for a DBMS.•discuss the contents of external, conceptual, and internal levels.•discuss the purpose of external/conceptual and conceptual/internal mappings.•explain the meaning of logical and physical data independence.•discuss the function and importance of the system catalogue.


Key Terms you must be able to use

If you have mastered this topic, you should be able to use the following terms correctly in your assignments and exams:

• Data Independence• External View• Conceptual View• Physical View• Record Based Model

• Hierarchical Model• Network Model• Relational Model

• Object Based Model

CT014-3-2 Database and Web Database Systems Database Architecture

Objectives of Architecture

• All users should be able to access same data.

• A user’s view is immune to changes made in other views.

• Users should not need to know physical database storage details.

Slide 6 (of 44)


Objectives of Architecture (2)

• DBA should be able to change database storage structures without affecting the users’ views.

Slide 7 (of 44)


Objectives of Architecture (3)

• Internal structure of database should be unaffected by changes to physical aspects of storage.

• DBA should be able to change conceptual structure of database without affecting all users.

Slide 8 (of 44)


ANSI-SPARC Architecture

Slide 9 (of 44)


ANSI-SPARC Architecture (2)

• External Level– Users’ view of the database. – Describes that part of database that is relevant to

a particular user.

• Conceptual Level– Community view of the database. – Describes what data is stored in database and

relationships among the data.

Slide 10 (of 44)



• Internal Level– Physical representation of the database on the

computer. – Describes how the data is stored in the database.

Slide 11 (of 44)



Slide 12 (of 44)


Data Independence

• Logical data independence– Refers to immunity of external schemas to

changes in conceptual schema– Conceptual schema changes (e.G.

Addition/removal of entities)– Should not require changes to external schema or

rewrites of application programs

Slide 13 (of 44)


Data Independence (2)

• Physical data independence– Refers to immunity of conceptual schema to

changes in the internal schema– Internal schema changes (e.G. Using different file

organizations, storage structures/devices)– Should not require change to conceptual or external

schemas

Slide 14 (of 44)


Data Independence (3)

Slide 15 (of 44)


Database Languages

• Data Definition Language (DDL)– Allows the DBA or user to describe and name

entities, attributes, and relationships required for the application

– plus any associated integrity and security constraints

Slide 16 (of 44)


Database Languages (2)

• Data manipulation language (DML)– Provides basic data manipulation operations on

data held in the database

• Procedural DML– Allows user to tell system exactly how to

manipulate data

• Non-procedural DML– Allows user to state what data is needed rather

than how it is to be retrieved

Slide 17 (of 44)


Database Languages (3)

• Fourth generation language (4GL)– Query languages– Forms generators– Report generators– Graphics generators– Application generators

Slide 18 (of 44)


Data Model

Integrated collection of concepts for describing data, relationships between data, and constraints on the data in an organization.

• Data model comprises:– A structural part;– A manipulative part;– Possibly a set of integrity rules.

Slide 19 (of 44)


Data Model (2)

• Purpose– To represent data in an understandable way

• Categories of data models include:– Object-based– Record-based– Physical

Slide 20 (of 44)


Data Model (3)

• Object-based data models– Entity-relationship– Semantic– Functional– Object-oriented

• Record-based data models– Relational data model– Network data model– Hierarchical data model

• Physical data models

Slide 21 (of 44)


Conceptual Model

• Conceptual schema is the core of a system supporting all user views.

• Should be complete and accurate representation of an organization’s data requirements.

• Conceptual modelling is process of developing a model of information use that is independent of implementation details.

• Result is a conceptual data model.

Slide 22 (of 44)


Functions of DBMS

• Data storage, retrieval, and update.

• A user-accessible catalogue.

• Transaction support.

• Concurrency control services.

• Recovery services.

Slide 23 (of 44)


Functions of DBMS (2)

• Authorization services.

• Support for data communication.

• Integrity services.

• Services to promote data independence.

• Utility services.

Slide 24 (of 44)


Components of DBMS

Slide 25 (of 44)


Component of Database Manager

Slide 26 (of 44)


Multi-user DBMS Architecture

• Teleprocessing

• File-server

• Client-server

Slide 27 (of 44)


Teleprocessing Architecture

• Traditional architecture.

• Single mainframe with a number of terminals attached.

• Trend is now towards downsizing.

Slide 28 (of 44)


Teleprocessing Architecture (2)

Slide 29 (of 44)


File Server Architecture

• File-server is connected to several workstations across a network.

• Database resides on file-server.

• DBMS and applications run on each workstation.

• Disadvantages include:– Significant network traffic.– Copy of DBMS on each workstation.– Concurrency, recovery and integrity control more complex.

Slide 30 (of 44)


File Server Architecture (2)

Slide 31 (of 44)


Client Server Architecture

• Server holds the database and the DBMS.

• Client manages user interface and runs applications.

• Advantages include:– Wider access to existing databases;– Increased performance;– Possible reduction in hardware costs;– Reduction in communication costs;– Increased consistency.

Slide 32 (of 44)


Client Server Architecture (2)

Slide 33 (of 44)


Client Server Architecture (3)

Slide 34 (of 44)


Catalogue Manager

• Repository of information (metadata) describing the data in the database.

• Typically stores:– Names of authorized users;– Names of data items in the database;– Constraints on each data item;– Data items accessible by a user and the type of access.

• Used by modules such as authorization control and integrity checker.

Slide 37 (of 44)


Information Resource Dictionary System (IRDS)

• Response to an attempt to standardize data dictionary interfaces.

• Objectives:– Extensibility of data;– Integrity of data;– Controlled access to data.

Slide 38 (of 44)


IRDS Interface Services

Slide 39 (of 44)


Quick Review Questions

Slide 40 (of 44)

• What is metadata?

• List any FIVE functions in a DBMS.

• List and explain any five major components of a database manager.

•List and explain three types of multi user database system architectures.


Follow Up Assignment

Slide 41 (of 44)

•We learnt only the concepts of database architecture. Conduct further research on the architecture of client server database architectures.


Summary

Slide 42 (of 44)

• ANSI-SPARC Database Architecture

•DBMS Functions

•DBMS Components

•Multi User DBMS Architecture


Question and Answer Session

Slide 43 (of 44)

Q & A


Next Session

Slide 44 (of 44)

Entity Relationship Modeling

topic2 databasearchitecture aug14

Documents

database architecturect014

level database architecture

web database systemsct014

internal structure of

database storage structures

type of architecture

physical data independence

conceptual levelcommunity