Drexel University
CS 451Software Engineering
Winter 2009
1
Yuanfang Cai
Room 104, University Crossings215.895.0298
Drexel University
Software Design Between Requirement and Coding Including:
Data Design Architectural Design Interface Design Component Design Detailed Design
Need to be modeled, analyzed, and reviewed in industrial strength software.
3
Drexel University
Translating the Analysis Model into the Design Model
4
Data/Class Design
Architecture Design
Interface Design
Component Design
Drexel University
Design Engineering Software design is an iterative process through
which requirements are translated into a “blueprint” for constructing software Abstraction Refinement
6
Drexel University
Design Engineering A design must implement all of the explicit requirements
contained in the analysis model, and it must accommodate all of the implicit requirements desired by the customer.
A design must be a readable, understandable guide for those who generate code and those who test and subsequently support the software.
The design should provide a complete picture of the software, addressing, the data, functional, and behavioral domains from an implementation perspective.
7
Drexel University
Design Quality FURPS – Functionality, Usability, Reliability,
Performance, and Supportability. Functionality – assessed by evaluating:
the feature set capabilities of the program.
Usability - assessed by considering: human factors, overall aesthetics, consistency, end-user documentation.
8
Drexel University
Design Quality - Functionality, Usability, Reliability, Performance, and Supportability
Reliability – is evaluated by measuring: the frequency and severity of failure, the accuracy, of output results, the mean-time-to-failure, the ability to recover from failure, the predictability of the program.
Performance – is measured by: processing speed, response time, resource consumption, throughput, efficiency
9
Drexel University
Design Quality - Functionality, Usability, Reliability, Performance, and Supportability
Supportability – combines: the ability to extend the program (extensibility), adaptability, serviceability testability, compatibility, configurability.
10
Drexel University
Design Concepts Abstraction
Architecture Patterns Data
Modularity Information Hiding Functional Independence Refinement Refactoring
Design Classes12
Drexel University
Design Concepts-Abstraction “Abstraction is one of the fundamental ways that
we as humans cope with complexity.” Grady Booch
“What kinds of things do we abstract? data objects procedures modules just about anything
13
Drexel University
Design Concepts-Architecture Software architecture alludes to “the overall
structure of the software and the ways in which that structure provides conceptual integrity for a system.
Architecture is: the structure or organization of program components
(modules), the manner in which these components interact, the structure of data that are used by the
components.
14
Drexel University
Design Concepts-Patterns “A pattern is a named nugget of insight which conveys
the essence of a proven solution to a recurring problem within a certain context amidst competing concerns.”
“Each pattern describes a problem which occurs over and over again in our environment, and then describes the core of the solution to that problem, in such a way that you can use this solution a million times over, without ever doing it the same way twice.” Christopher Alexander
15
Drexel University
Design Concepts -Modularity MODULARITY
“Modularity is the single attribute of software that allows a program to be intellectually manageable”
Software is divided into separately named and addressable components, sometimes called modules, that are integrated to satisfy problem requirements.
16
Drexel University
Design Concepts –Information Hiding Modules should be specified and designed so that
information (algorithms and data) contained within a module is inaccessible to other modules that have no need for such information.
This means that inadvertent errors introduced during modification are less likely to propagate to other locations within the software.
Changes to the internal representation of one module should have not have an effect on other modules.
17
Drexel University
Design Concepts-Functional Independence
Functional independence is achieved by developing modules with “single-minded” function and an “aversion” to excessive interaction with other modules.
We want to design software so that each module addresses a specific subfunction of requirements and has a simple interface when viewed from other parts of the program structure.
18
Drexel University
Design Concepts-Functional Independence Independence is assessed by using two
qualitative criteria: Cohesion – How related a module is to itself. It should
perform a single task and require little interaction with the rest of the program.
Coupling is an indication of the interconnectoin among modules in a software structure.
19
Drexel University
Design Concepts-Refinement Stepwise refinement is when a program is
developed by successively refining levels of procedural detail.
Refinement is actually the process of elaboration.
20
Drexel University
Design Concepts-Refactoring Refactoring is a reorganizational technique that
simplifies the design )of code) of a component without changing its function or behavior.
21
Drexel University
Design Concepts-Design Classes Refine analysis classes by providing design details
Create a new set of design classes that implement a software infrastructure to support the business solution
Five types: User interface classes Business domain classes Process classes Persistent classes System classes
22
Top Related