Sw Software Design

SW Software Design SW

Design

Architecture

High Level Design

Module Decomposition

Functional/OO

Design Document/IEEE Std.1016 SDD

Detailed Design

Formal Methods

UML

Overview

Graphical Diagrams

Architectural Design

Establishing basing structural framework of an application - decomposition ( subsystems, modules ), interface specification and communication .

subsystems - independent components/modules of an application

modules - provide one or more services to other modules

Output - Design Document/SDD

Architecture Design Choice

Affects: performance, robustness, distributabilty and maintainability and development costs .

Application Constraints:

Performance

localize critical operations

Security

access control, layered structure

Safety

costly validation, single component for safety-related operations

Availability

include redundant components

Maintainability

self-contained components

Structure Design

Repository Design

Client-Server Design

Layered Design

Control Models

Centralized control

Hierarchic Design

Centralized Design

Event Driven

Broadcast

Interrupt driven

Repository Design Registrar Staff Professor Client Admin Client Student Database Professor Database Schedule Class Database Adv : - share large database - integrate tools w/ same data model Drbk : - performance - evolution difficult - forces the same policy on subsystems - difficult to distribute Student Client

Client/Server Design Registrar Staff Student Database Professor Database Schedule Class Database Payroll HR Adv : - distributed - scalable Drbks : -naming/registry -diff to anticipate prbls w/ add a srvr -independent data mgmt/recovery Student Client Professor Client

Layered Design Kernel Memory Mgmt I/O - Dev.Drv File Server - GUI Adv : - incremental dev. - portability

Hierarchic Control Design Adv : - call/return - only for sequential tasks

Centralized Design Adv : - parallel tasks - RTS System Controller Input Sensor Program Program/Data

Broadcast Design network Client A Client B Client C Client D

Interrupt Design IH 2 Proc IH 3 Proc IH 5 Proc IH 4 Proc IH 1 Proc Adv : - fast Drbks : -complex to implement/test/validate

Design Entities

Procedural design

Procedures

Modular design

Modules

Object-oriented design

Classes

Multithreded, multiprocessors, multitasking

Threads, tasks, processes

Compiler: Functional view Lexical analysis Syntax analysis Semantic analysis Build symbol table Code generation input program program symbols symbolic program syntax tree symbol table analyzed program Object code

Compiler: Object oriented view Source program Syntax tree Symbol table Analyzed program Object code

Software Design Process Requirements Specification Architectural Design Functional Specification Architecture Chart UI Design Module/Algorithm Design UI Specification Database Design Module/Algorithm Specification Database Specification Design Activities API, algorithms database

Design Methods

Informal ad hoc

Formal requirements

Formal specifications

Structured

Models supported

data-flow model - data transfers

entity-relation model - basic entities and relations

structural model - components and interactions

object-oriented model - objects, relationships and interactions, classes/methods

C++/Java C++ Classes, variables, functions class myclass { int myclassvariable; public: int myclass (int); ~myclass(); void function(int i) } Java Classes, variables, methods public class myclass { int myclassvariable; myclass (int){}; void function(int i){}; }

Architecture Chart HTML GUI WML GUI SQL Database Server WAP Terminal Web Terminal JDBC HTML WML Template files ASCII

Design Document Outline

Software program overview

broad terms overview, high level discussion of the design alternatives.

goals for the architecture, problem addressed.

Subprograms and organization chart

major clusters of functionality, communication and dependencies.

Change scenarios

most likely changes in the program and how each change will be addresses.

Reuse analysis and buy vs build decisions

arguments for what will be build, bought or reused.

Approach to Standard Functional Areas

External software interfaces ( APIs )

User interface - prototype

Database organization - content, type of database

Data storage - non database data, file formats, major data structures

Key algorithms

Memory management

String storage - stiles, error messages

Concurrency/threads

Security - how the design will be affected

Localization

Networking - multi-user

Portability

Programming language

Error handling

IEEE Design Description Overview Std. 1016

SDD: Standard Design Description

Introduction

Decomposition Description

Dependency Description

Interface Description

Detailed Design Description

SDD Modular Design Methodology

Introduction

Purpose

Scope

Definitions and acronyms

References

Overview

Module Decomposition

Module 1 Description

Module 2 Description

…

Task Decomposition

Task 1 Description

Task 2 Description

…

3. Dependency Description

Module dependency Description

Task Dependency Description

4. Interface Description

Module Interface Description

Module 1 Interface Description

Module 2 Interface Description

…

Task Interface Description

Task 1 Interface Description

Task 2 Interface Description

…

5. Detailed Design Description

Module Detailed Description

Module 1 Detailed Description

Module 2 Detailed Description

…

Task Detailed Description

Task 1 Detailed Description

Task 2 Detailed Description

…

SDD Object Design Methodology

Introduction

Purpose

Scope

Definitions and acronyms

References

Overview

Class 1 Description

Class 2 Description

…

SDD Object Design Methodology

3. Dependency Description

Object Interaction Description

Aggregation Description

Inheritance Description

4. Interface Description

Class 1 Interface Description

Class 2 Interface Description

…

5. Detailed Design Description

Class 1 Detailed Description

Class 2 Detailed Description

…

Detailed Design Formal Design Approach Formal Design Approach Very Formal Design Approach Informal Design Approach

for a subprogram/module/object

done by the developer

Project difficulty Programmer experience HIGH LOW HIGH LOW

Formal Methods

(theory, logic, algebra). Large % of the software developed use formal methods.

Formal specifications

Way of discovering specification errors and presenting the application specification in a unambiguous way -fewer errors.

Specification analysis and proof

Application verification/validation

Critical Software Applications Development

Costs of failure are high -

Properties: safety, reliability, security .

Have high validation costs.

Examples:

Air traffic control system ( Hall 1996 )

Railway signaling systems ( Dehbonei and Mejia, 1995 )

Spacecraft systems ( Easterbrook 1998 )

Medical control systems ( Jackey 1997 )

Software tool specification ( Neil 1998 )

IBM’s CICS system ( Wordsworth 1991 )

UML Overview

UML

Modeling language for specifying, visualizing, constructing and documenting software programs.

Model elements, Notation and Guidelines

Motivation

communication among project teams

tools for automation of software design/validation/production (same as component technology, visual programming)

SW Program

A set of nearly independent set of graphical diagrams

UML Graphical Diagrams

Use Case Diagram

Static Structure Diagrams

Class/Object Diagram

Behavior Diagrams

Interaction Diagrams

Sequence diagram

Statechart Diagrams

Activity Diagrams

Implementation Diagrams

Component Diagram

Deployment Diagram

Use Case Diagram

Display the user interaction with the application

Provide an external view of the application

Basis for testing

Use Case Relationships

Include - to avoid repetition of use cases

Generalization - describe a variation casually

Extend - declare extension points in the base case

Use Case Diagram Check Grade Register Classes Database Query Authorize Student Input Grades Student Professor Registrar Staff Max Credits <<include>> <<include>> <<include>> <<include>> Include Generalization Use Case

Class Diagram

Describes the type of objects and the static relationships ( associations and subtypes )

Class

attributes, multiplicity, generalization, role, constraints, operations

Associations

relations between instances of classes, with multiplicity (*, x, x..y | x, y  N)

navigability (unidirectional/bi-directional)

Class Diagram Catalog Entry exam date : Date grade : String passed():Boolean Class subject : String professor : String gradedPNP():String 1 * * 1 If CatalogEntry.Student.isCurrent is “n” then Catalog.Entry.grade must be “N” Multiplicity: mandatory Association Generalization Class Constraint Job 0..1 Multiplicity: optional Attribute Operation Multiplicity: Many-valued Navigability Student name : String address : String ID : Long Integer isCurrent():String Graduate department: String isCurrent():String Undergraduate major: String isCurrent():String

Object/Class Diagrams

Object diagram

objects allocated at a certain point in time

Classification -relation of an object to a type

Single classification - single type, subtypes

Multiple classification - several types

Static classification - separation between types/states

Dynamic classification - change type within the subtyping structure

Object/Class Diagrams Employee name Male Female Developer QA/Test Design Job <<dynamic>> Sex {complete} Discriminator Manager Software: MGMT name = “Name” MGMT * 1 Software PM: MGMT name = “Name” QA Manager: MGMT name = “Name” Software PM: MGMT name = “Name” Engineer: Developer name = “Name” Engineer: Design name = “Name” Engineer: QA/Test name = “Name” Engineer: Developer name = “Name” Object Diagram showing instances of the above class diagram Class Diagram with Multiple and Dynamic Classification Sex: M/F Sex: M/F Sex: M/F Sex: M/F Sex: M/F Sex: M/F Sex: M/F Sex: M/F

Statechart Diagram

All possible states that a particular object can get into

How the object state changes as a result of events that reach the object

Enhancements

Superstates

Concurrent Statechart Diagrams

Statechart Diagram State C State B State A State D -describes the behavior of a model element such as an object or interaction Trigger condition A to B Trigger condition B to D Trigger condition C to A Trigger condition C to B Trigger condition B to C start self-transition transition state

Sequence Diagram

Shows a number of example objects and the messages that are passed between these objects within the use case

Time on the vertical dimension and different objects on the horizontal dimension

Also valuable for concurrent processes

Sequence Diagram Initiate request Init servlet new Gdocument(); Connect to the database servlet.setDomaine(); servletgetConnection(); HTTP request on the server TCP/IP port 80 Database call prepareStatement() executeQuerry() Response to the SQL request Database call return Read data getString(); Generate HTML output doc.p(); HTML return return(); Display WEB page Web Client Web Server Database

Activity Diagram

A state machine of the procedure itself, the states represent the performance of actions or subactivities and the transitions are triggered by the completion of the actions or subactivities

Branch - conditional behavior, a single incoming transition and multiple outgoing transitions

Merge - multiple input transitions and one single output

Fork - parallel activities, one incoming transition and several outgoing transitions

Join - multiple input transitions and one single output

(*) Dynamic concurrency

Swimlanes - for clarity

Recommended for:

analyzing a use case, understanding workflow, describing a complicated sequential algorithm, dealing with multithreaded applications

Activity Diagram Present lecture Prepare slides Turn on the projector Tune the projector [found projector] [no projector] Use blackboard Begin lecture Start Fork Join End

Component Diagram

Structure of the code

Shows various components of the application and their dependencies

Component

a physical module of the code

Dependencies

how changes to one component may cause other components to change

Component Diagram WML Interface Search Engine Database query

Deployment Diagram

Structure of the run time program

Physical relationships among software and hardware components

Node - a computational unit - in most cases a hardware device

Connection - communication path over which nodes interact

Deployment Diagram WAP Terminal WML Interface Server Search Engine Database query Component Communication Interface Application Connection Contained object(s) Node