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Software Quality Assurance

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Presentation on theme: "Software Quality Assurance"— Presentation transcript:

1 Software Quality Assurance

2 Recap What is SQA? What is quality? Different Terminologies
Cost of correcting an error Elements of SQA

3 SQA Goals, Attributes and Metrics
Number of ambiguous modifiers (e.g., many, large, human-friendly) Number of TBAs, TBDs Number of sections/subsections Number of changes per requirement Time (by activity) when change is requested Number of requirements not traceable to design/code Number of UML models Number of descriptive pages per model Number of UML errors Existence of architectural model Number of components that trace to architectural model Complexity of procedural design Layout appropriateness Number of patterns used Goals Requirement quality Design quality Attributes Ambiguity Completeness Understandability Volatility Traceability Model clarity Architectural integrity Component completeness Interface complexity Patterns

4 SQA Goals, Attributes and Metrics
Cyclomatic complexity Design factors Percent internal comments Variable naming conventions Percent reused components Readability index Staff hour percentage per activity Actual vs. budgeted completion time Review metrics Number of errors found and criticality Effort required to correct an error Origin of error Goals Code quality QC effectiveness Attributes Complexity Maintainability Understandability Reusability Documentation Resource allocation Completion rate Review effectiveness Testing effectiveness

5 SQA plan Management section Documentation section
describes the place of SQA in the structure of the organization Documentation section describes each work product produced as part of the software process Standards, practices, and conventions section lists all applicable standards/practices applied during the software process and any metrics to be collected as part of the software engineering work Reviews and audits section provides an overview of the approach used in the reviews and audits to be conducted during the project Test section references the test plan and procedure document and defines test record keeping requirements Problem reporting and corrective action section defines procedures for reporting, tracking, and resolving errors or defects, identifies organizational responsibilities for these activities Other tools, SQA methods, change control, record keeping, training, and risk management

6 Statistical SQA Information about software defects is collected and categorized An attempt is made to trace each defect to its underlying cause Isolate the vital few causes of the major source of all errors Then move to correct the problems that have caused the defects

7 Statistical SQA – Categories of errors
Incomplete or erroneous specification (IES) Misinterpretation of customer comm (MCC) Intentional deviation from specification (IDS) Violation of programming standards (VPS) Error in data representation (EDR) Inconsistent module interface (IMI) Error in design logic (EDL) Incomplete or erroneous testing (IET) Inaccurate or incomplete documentation (IID) Error in programming lang. Translation (PLT) Ambiguous or inconsistent human-computer interface (HCI) Miscellaneous (MIS) Most often IES, MCC and EDR are the vital few causes for majority of errors.

8 Identifying the vital few

9 Statistical SQA

10 Example

11 Statistical SQA – Six Sigma
Most widely used strategy for statistical SQA Three core steps Define customer requirements, deliverables and project goals via well-defined methods of customer communication Measure the existing process and its output to determine quality Analyze defect metrics and determine the vital few causes If an existing software process is in place, but improvement is required six sigma suggests Improve the process by eliminating the root causes of defects Control the process to ensure that future work does not reintroduce the cases of defects If an organization is developing a software process, the core steps are augmented Design the process to (1) avoid the root causes of defects and (2) to meet customer requirements Verify that the process model will, in fact, avoid defects and meet customer requirements

12 Reviews To uncover errors/defects
To uncover errors in function, logic, or implementation for any representation of the software To verify that software meets its requirements To ensure that software representation meets predefined standards To achieve software development in a uniform manner To make projects more manageable

13 Review Roles Presenter (designer/producer).
Coordinator (not person who hires/fires). Recorder records events of meeting builds paper trail Reviewers maintenance oracle standards bearer user representative others

14 Formal Technical Reviews
Involves 3 to 5 people (including reviewers) Advance preparation (no more than 2 hours per person) required Duration of review meeting should be less than 2 hours Focus of review is on a discrete work product Review leader organizes the review meeting at the producer's request. Reviewers ask questions that enable the producer to discover his or her own error (the product is under review not the producer) Producer of the work product walks the reviewers through the product Recorder writes down any significant issues raised during the review Reviewers decide to accept or reject the work product and whether to require additional reviews of product or not.

15 Formality and Timing Formal review presentations
resemble conference presentations. Informal presentations less detailed, but equally correct. Early tend to be informal may not have enough information Later tend to be more formal Feedback may come too late to avoid rework

16 Formality and Timing Analysis is complete. Design is complete.
After first compilation. After first test run. After all test runs. Any time you complete an activity that produce a complete work product.

17 Why do peer reviews? To improve quality.
Catches 80% of all errors if done properly. Catches both coding errors and design errors. Enforce the spirit of any organization standards. Training and insurance.

18 Review Guidelines.. Review the product, not producer
Set an agenda and maintain it Limit the debate Enunciate problem areas, not to solve every problem noted Take written notes Allocate resources and time schedule for FTR’s Use standards to avoid style disagreements. Let the coordinator run the meeting and maintain order. Limit the number of participants and insist upon advance preparation Develop a checklist for each work product to be reviewed Training for all reviewer’s Reviewing earlier reviews Keep it short (< 30 minutes). Don’t schedule two in a row. Don’t review product fragments.

19 Effectiveness of review  Defect Amplification and Removal
Used to illustrate the generation and detection of errors during design and code generation Errors passed through Amplified errors 1:x Newly identified errors Percent efficiency for error detection Errors from previous steps Errors passed to next step Development step Defects Detection

20 Effectiveness of review  Defect Amplification and Removal
No reviews With reviews

21 Effectiveness of review  Defect Amplification and Removal

22 Review metrics and their use
Many metrics can be defined for technical reviews The following can be calculated for each review conducted: Preparation effort (Ep) Assessment effort (Ea) Rework effort (Er) Work product size (WPS) Minor errors found (Errminor) Major errors found (Errmajor)

23 Summary SQA goal, attributes and metrics SQA plan
Formal Technical Review (FTR) Statistical SQA Six Sigma Identifying vital few causes Review efficiency

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