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Software Metrics

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  1. Software Metrics byAmr KamelPhD Student in Software EngineeringDepartment of Computing ScienceUniversity of Alberta

  2. Introduction ‘You can’t control what you can’t measure’ Tom DeMarco • Required Qualities of a technical system: • Functionality - e.g correctness, reliability. • Performance - e.g. response time, throughput. • Economy - e.g cost effectiveness. CMPUT 401

  3. Definition • Mathematical: • A function that measures the distance between two objects in a set. • Software: • Measure for the software qualities - a mapping from artifacts to a measurement scale. CMPUT 401

  4. Metrics Goals • The goal is to identify and measure the essential parameters that affect software development: • Estimate • Cost and Effort for: • a particular period. • particular artifact. • Plan • Development aspects • Control • Quality aspects. CMPUT 401

  5. Characteristics of Good Metrics • For a single metric: • Simple. • Objective. • Easily obtained - (automated?). • Valid. • Robust. • For a metrics model: • Consistent. • Complete. CMPUT 401

  6. State of Software Metrics • What are we measuring? • There are no “universally accepted” set of metrics. • Lack of sound theoretical basis. • Lack of universally defined primitives. • Various models use different set of parameters. CMPUT 401

  7. Classification • Product versus Process. • Objective versus Subjective. • Primitive versus Computed. CMPUT 401

  8. Category: Size Complexity Quality Inheritance Coupling and Uses Reuse Granularity System Class Method Product Metrics CMPUT 401

  9. Object Oriented Paradigm • Size: • System: Number of classes • Class: Number of methods • Method: LOC • Complexity: • System: Number of edges in the class hierarchy chain. • Class: Counts of parents, children, progeny • Method: MCC • Quality: • Defect count and MTTF (Mean Time To Failure) CMPUT 401

  10. Object-Oriented Paradigm • Inheritance: • Depth of inheritance tree. • Coupling and uses • Number of accesses to (or by) other classes. • # of cooperating classes. • Reuse: • “as-is” reuse (methods, classes, system). • “adapted” reuse. CMPUT 401

  11. Process Metrics • Time (elapsed time, consumed time). • Effort (person-month). • Personnel (experience, continuity, etc.). • Development setup (tools, programming language, schedule requirements, etc). CMPUT 401

  12. Metrics Models • Empirical: • Wolverton (1974) • Statistical: • Walston & Felix (1977) • Theory-based • Rayleigh model (1978) • Composite • COCOMO model (1981) CMPUT 401

  13. Wolverton Model • Modules are classified into types. (control, I/O) • Each module is categorized as: • Hard, Medium, Easy and • Old, New. • Module size are estimated. • Cost is estimated based on historical data. CMPUT 401

  14. COCOMO Model • a & b are constants - determined for each model and model level. • S is program size in KLOC • m is a composite multiplier determined by 17 cost-drivers grouped in 4 categories: • Product, platform, personnel and project. CMPUT 401

  15. Problems With Metrics Models • Model validity. • Need for sound statistical methods. • Need for experimentation. • Scaling, environment effect. • Data: collection, availability. CMPUT 401

  16. Process Maturity- Benchmarking • Characterization for process practices W.R.T. Industry best practices. • Fundamental to the characterization is the use of statistical control. CMPUT 401

  17. Process Maturity Models • HealthCheck (BT), Trillium (Cantel). • ISO 9000 (ISO 9000-3, ISO 9001) • Capability and Maturity Model (CMM) • Software Process Improvement and Capability dEtermination (SPICE) - ISO 15504. CMPUT 401

  18. Enacting Metrics Programs Standardize Define Objectives Plan Act Check Do Propose a Model, Action Plan Success Indicators CMPUT 401

  19. Enacting Metrics Programs • Plan. • Identify your customer. • Identify the attacked problem(s) and identify goals. • Estimate costs. • Do. • Choose a model. • Define and detail required data. • Provide tools & training. CMPUT 401

  20. Enacting Metrics Programs • Check. • Establish quality criteria for the program. • Implement the program on a sample project. • Act. • Institutionalize the program. CMPUT 401

  21. Dos & Don’t In Quality Improvements • Dos: • Provide training & support. • Ensure management support. • Set realistic expectations. • Don’ts: • Separate quality assurance and development. • Manage by fear or break team morals. • Show progress rather than make progress. CMPUT 401

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