meljun cortes jedi slides-4.6 component-level design

7/31/2019 MELJUN CORTES JEDI Slides-4.6 Component-Level Design

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Software Engineering 1

Design Engineering

Component-levelDesign

TOPIC SIX


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Component-level Design

It defines the data structure, algorithms, interfacecharacteristics, and communication mechanism allocated toeach software component.

A component is the building block for developing computersoftware. It is a replaceable and almost independent part ofsoftware that fulfills a clear function in the context of a well-defined architecture.


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Basic Component Design

Principles The Open-Close Principle

Components should be extended without the need to modify theinternal structure and behavior of the component.

Liskov Substitution Principle A class can use the derived class as a substitute to the base class.

Dependency Principle

Class should be dependent on abstractions.

Interface Segregation Principle Develop classes that are specific rather than general purpose.


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Guidelines Component

Architectural component names should come from the problemdomain and is easily understood by the stakeholders, particularly,the end-users. As an example, a component called Application is

clear to any one reading the component. Implementation component name should come from the

implementation specific name. As an example, Athlete is thepersistent class for a record of an athlete.

Use stereotypes to identity the nature of the component such as

, or .


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Guidelines Interfaces

The canonical representation of the interface is recommended whenthe diagram becomes complex.

They should flow from the left-hand side of the implementingcomponent.

Show only the interfaces that are relevant to the component underconsideration.

Dependencies and Inheritance

Dependencies should be modeled from left to right. Inheritance should be modeled from bottom (subclass or derived

class) to top (superclass or base class).

Component interdependence are modeled from interface to interfacerather than component to component.


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Component Diagram

It is a diagram used to model software components, theirdependencies, hierarchies and interfaces.


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Developing the Software

Components1. Refine all classes.a) If necessary, redefine the sequence and collaboration diagrams.

b) Distribute the operations and refine the operation signature.

c) Refine attributes of each class.

d) Identity visibility.

e) Document the class.

2. Refine the packaging of the classes.

3. Define the software components.


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STEP 1: Refine all classes.

The classes are refined in such a way that they are unifiedand at the same time, it can be easily translated into aprogram.

Steps involved are:

Refine the sequence and collaboration diagrams if necessary.

Distribute and refine the operation signatures.

Refine attributes.

Identify visibility of attributes and operations.

Document the class.


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MaintainAthleteRecord

Hierarchy


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Attribute and Operation

Visibility Visibility specifies whether an attribute or operation is or is notaccessible.

It uses the following symbols.

VisibilitySymbols

Descriptions

+PUBLIC. The attribute or operation isdirectly accessible to an instance of aclass.

-PRIVATE. The attribute or operation isonly accessible to the instance of theclass that includes it.

#

PROTECTED. The attribute or

operation may be used either byinstances of the class that includes it orby a subclass of the class.

~PACKAGE. The attribute or operationis only accessible only be instances of aclass in the same package.


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Sample Controller Class

Definition


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STEP 2: Refine the packaging

of the classes. It might be necessary to redistribute the classes among the

layers and partitions of the software architecture.


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STEP 3: Define the software

components. Packages are the software components.


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Club Membership

Maintenance Components User Interface Package (abl.athlete.ui) AthleteRecordUI.java

AthleteListUI.java

FindAthleteRecordUI.java Controllers (abl.athlete.con)

MaintainAthleteRecord.java

AddAthlete.java

EditAthlete.java DeleteAthlete.java

FindAthleteRecord.java


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Club Membership

Maintenance Components DBClasses (abl.athlete.dbclass) DBAthlete.java

Persistent Classes (abl.athlete.pc)

Athlete.java Guardian.java

PCLAthlete.java


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Summary

Basic Component Design Principles Component-level Design Guidelines

Component Diagram

Developing the Software Component Design

meljun cortes jedi slides-4.6 component-level design

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