University:
California State University, Northridge
Course:
COMP 684 | Software Architecture and Design
Academic year:

2024
Views:

120

Pages:

16
Author:

Beckett Gray

Quality Models and Quality Attributes Part 2 The McCall/GE Model Factors  Factors (characteristics) describe the external view of the software as viewed by users of the application.  Product operation factors      Accuracy Reliability Efficiency Integrity Usability The McCall/GE Model Factors (Cont’d)  Product revision factors    Maintainability Flexibility Testability  Product transition factors    Interface facility Reusability Transferability Additional Factors from Boehm  Validity  Clarity  Understandability  Modifiability  Modularity  Generality  Economy  Resilience  Documentation DeGrace and Stahl – Software Engineering Practices  Coding practices  Management practices  Use of design heuristics Laurence Best’s Application Architecture  One of the first attempts at applying quality characteristics to architecture  Previously models did not focus on architecture but rather the entire process and product of software engineering  Best’s characteristics   Accuracy and comprehensiveness Simplicity of use Laurence Best’s Application Architecture (Cont’d)  Best’s characteristics (cont’d)      Operational flexibility Ease of development, maintenance, and extension Security and control Resource efficiency Recovery Bass, Clements, and Kazman Categories for Quality Attributes  Observable via execution  Not observable via exceution  Each of these is divided into three subcategories:    System attributes Business qualities Architecture description qualities Bass, Clements, and Kazman Categories for Quality Attributes (Cont’d)  Observable via execution  Not observable via execution  The following attributes may be observed by executing the system;      Performance Security Availability Functionality Usability Bass, Clements, and Kazman Categories for Quality Attributes (Cont’d)  Usability is composed of six quality attributes:       Learnability Efficiency Memorability Error avoidance Error handling Satisfaction Bass, Clements, and Kazman Categories for Quality Attributes (Cont’d)  The following are not observed by executing the system:      Modifiability Portability Reusability Integrability Testability Bass, Clements, and Kazman Categories for Quality Attributes (Cont’d)  Some quality attributes are business related:      Time to market Cost Targeted market Rollout schedule Extensive use of legacy systems Bass, Clements, and Kazman Categories for Quality Attributes (Cont’d)  In the SEI quality model, quality attributes have three characterizations:    External stimuli, Architectural decisions Responses  The requirements need to be specified in such a way as to be observable.  For example, maintainability should be specified as concrete change scenarios that a software developer would do to modify the system. The ISO/IEC 9126 Standard  The six characteristics are:       Functionality Reliability Usability Efficiency Maintainability Portability Benefits of Quality Models  The ISO/IEC 9126 identifies the following uses of a quality model:      Validate the completeness of a requirements definition Identify software requirements Identify software design objectives Identify software testing objectives Identify user acceptance criteria for a completed software product Benefits of Quality Models (Cont’d)  A quality model that defines quality attributes precisely improves communications between acquirers, architects, and developers.  A quality model that specifies usable and practical metrics can improve the quality of design models.  Effective application of a quality model adds more quality control earlier in the project’s life cycle.

Quality Models and Quality Attributes, Part 2

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