Software design quality ppt

Help Preferences Sign up Log in. View by Category Toggle navigation. Products Sold on our sister site CrystalGraphics. Title: Software Quality Metrics. Communicativeness The degree to which software is designed in accordance with Tags: communicativeness metrics quality software. Latest Highest Rated.

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Is vc still a thing final. Related Books Free with a 30 day trial from Scribd. Related Audiobooks Free with a 30 day trial from Scribd. Empath Up! Software quality 1. In a practice the quality of a system can be a vague, undefined, attribute. We therefore need to define precisely what qualities were require of a system.

However, this is not enough — we need to objectively weather a system meet out quality requirements and this need measurement. Quality will be of concern at all stages of project planning and execution. Software Quality 0. Select Project 1. Identify 2. Identify Project scope Project and objective Infrastructure 3. Analyze project characteristics 4. Identify the projects and activities Lower 5. Estimate Level Planning efforts for activity 9. Execute 6. Identify Plan activity risk 8.

Identify Project Scope and objective: Some objective could relate to the qualities of the application to be delivered. Identify project infrastructure: Identify the installation standard and procedures. Some of these almost certainly be about quality 3. Analyze project characteristics: To identify the other qualities based requirement. Identify the products and activities of the project: It is at this point the entry, exist and process requirement are identified for each activity 5.

In general the later in a project that an error is found the more expensive it will be to fix. In addition because the number of errors in the system is unknown, the debugging phases of a project are particularly difficult to control Attempt to identify specific product qualities that are appropriate to software, for instance, grouped software qualities into three sets.

Product operation qualities, Products revision qualities and product transition qualities. Product revision qualities Maintainability: the effort required to locate and fix an error in an operational program Testability: The effort required to test a program to ensure it performs its intended function Flexibility: The effort required to modify an operational program, Product Transition qualities Portability: The efforts required to transfer a program from one hardware configuration and or software system environment to another Reusability: The extent to which a program can be used in other applications.

During quality is not enough. If we are to judge whether a system meets out requirements we need to be able to measure its qualities. For each criterion, one or more measure have to be invented the degree to which the quality is present. In general the user of software would be concerned with measuring what McCall called quality factors while the developers would be concerned with quality criteria.

The following should be laid down for each quality. Functionality: which covers the functions that a software product provides to satisfy user needs. Functionality sub characteristics: suitability, Accuracy, Interoperability, Compliance and Security. Compliance refers to the degree to which the software adheres to application- related standards or legal requirements. Typically these could be auditing requirement.

Interoperability refers to the ability of software to interact with others. Reliability: Which relates to the capability of the software to maintain its level of performance Reliability sub characteristics: Maturity, Fault Tolerance and recoverability. Maturity refers to frequency of failures due to fault in software more identification of fault more chances to remove them.

Usability: Efforts need to use a software. Usability sub characteristics: Understand ability, Learnability, operability. Understand-ability is a clear quality to grasp, although the definition attributes that bear on the user efforts for recognizing the logical concept and its applicability in our view actually makes it less clear.

Learnability has been distinguished from operability. A software tool might be easy to learn but time- consuming to use say it uses a large number of nested menus. This is for a package that is used only intermittently but not where the system is used or several hours each day by the end user. In this case learnability has been incorporated at the expense of operability. Efficiency: physical resource used when a software is executed Efficiency sub characteristics: Time behaviour, Resource behaviour.

Maintainability: Effort needed to the make changes to the software Maintainability sub characteristics: Analysability, Changeability, Stability and Testability. Analysability is the quality that McCall called diagnose ability, the ease with which the cause of failure can be determined.

Changeability is the quality that other have called flexibility: the latter name is perhaps a better one as changeability has a slightly different connotation in plain English It implies that the suppliers of the software are always changing it.

Coupling measures the interdependence of two modules while cohesion measures the independence of a module. If modules are more independent, they will be less dependent upon others.

Therefore, a highly cohesive system also implies less coupling. Modules with high cohesion and low coupling can be treated and analyzed as black boxes. This approach therefore allows us to analyze these boxes independent of other modules by applying the principle of separation of concern.

This diagram depicts two systems, one with high coupling and the other one with low coupling. The lines depict linkages between different components.

In the case of highly coupled system, module boundaries are not well defined, as everything seems to be connected with everything else. On the other hand, in the system with low coupling modules can be identified easily.

In this case intra component linkages are stronger while inter component linkages are weak. The modules that interact with each other through message passing have low coupling while those who interact with each other through variables that maintain information about the state have high coupling. That means, in case some kind of change is required in the software, all the related pieces are found at one place.

A class will be cohesive if most of the methods defined in a class use most of the data members most of the time. If we find different subsets of data within the same class being manipulated by separate groups of functions then the class is not cohesive and should be broken down as shown below. Posted by Unknown at AM. Labels: Software Design. No comments:. Newer Post Older Post Home.