Quality Measurable characteristic Cyclomatic complexity Cohesion Coupling Quality of design Requirements, specifications, and design Quality of conformance Implementation – if it follows the design then the resulting system meets its goals – conformance quality is high Are there any other issues? Glass User satisfaction = compliant product + good quality + delivery within budget and schedule DeMarco – “A product quality is a function of how much it changes the world for the better”

Recap

Software Engineering II Lecture 27 Fakhar Lodhi

Cost of quality Cost of prevention, appraisal, and failure Prevention Quality planning Formal technical reviews Test equipment Training Appraisal – includes activities to gain insight into the product condition In-process and inter-process inspection Testing

Failure cost Internal failure cost Rework Repair Failure mode analysis External failure cost Complaint resolution Product return and replacement Help-line support Warranty work Law suits Cost increases as we go from prevention to detection to internal failure to external failure

A case A total of 7053 hours were spent inspecting 200,000 lines of code with the result that 3112 potential defects were prevented. Assuming a programmer cost of $40 per hour, the total cost of preventing 3112 defects was $382,120, or roughly $91 per defect

Compare these numbers to the cost of defect removal once the product has been shipped to the customer. Suppose that there had been no inspections, and the programmers had been extra careful and only one defect one 1000 lines escaped into the product shipment. That would mean that 200 defects would still have to be fixed in the field. As an estimated cost of $25000 per fix, the cost would be $5 Million or approximately 18 times more expensive than the total cost of defect prevention Quality translates to cost savings and an improved bottom line.

Quality Control Variation control is the heart of quality control Resource and time estimation Test coverage Variation in number of bugs Variation in support From one project to another we want to minimize the predicted resources needed to complete a project and calendar time.

Quality Control Involves series of inspection, reviews, and tests Includes feedback loop Combination of measurement and feedback Combination of automated tools and manual interaction

SQA Activities Involves two different groups Software engineers who do the technical work SQA group who is responsible for QA planning, oversight, record keeping, analysis, and reporting

SQA Group Activities SQA Group develops an SQA plan for the project during project planning Plan is reviewed by all stake holders Plan includes the identification of: Evaluations to be performed Audits and reviewed to be performed Standards that are applicable to the project Procedures for error reporting and tracking Documents to be produced by the SQA group Amount of feedback provided to the software project team

SQA Group participates in the development of the project’s software process description The software team selects the process SQA reviews the process description for compliance with the organizational policies, internal software standards, externally imposed standards, and other parts of the software project plan

SQA Group reviews software engineering activities to verify compliance with the defined software process Identifies, documents, and tracks deviations from the process and verifies that the corrections have been made

SQA Group audits designated software work products to verify compliance with those defined as part of the software process Reviews selected work products, identifies, documents, and tracks deviations; verifies that corrections have been made; and reports the results of its work to the project manager

Ensures that deviations in software work and work products are documented and handled according to the documented procedures. Deviations may be encountered in the project plan, process description, applicable standards, or technical work products

Records any non-compliance and reports to senior management Non-compliant items are recorded and tracked until they are resolved. Coordinates the control and management of change and helps to collect and analyze software metrics