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CS 501: Software Engineering Fall 1999

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CS 501: Software Engineering Fall 1999

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  1. CS 501: Software EngineeringFall 1999 Lecture 22 (a) Managing the Software Process (b) Software Reuse

  2. Administration  Assignment 5 due date changed  No recitation next week

  3. Cost Estimation See Sommerville, Chapter 29 Categories of cost:  Hardware and software  Professional staff (salaries and benefits)  Miscellaneous (e.g., travel and training)  Indirect (e.g., space, support staff, technical infrastructure, marketing and management)  Profit

  4. Cost Estimation The challenges in cost estimation are:  How long will it take?  How many people will be required? These are reflected in the costs for:  Professional staff  Indirect costs

  5. Pricing For in-house development, costs and pricing are directly related by some formula. Example: Federally funded university research For commercial development, price charged may differ from costs:  Market penetration (new fields, foot in door)  Contingency to cover uncertainty  Ownership of software product  Financial health

  6. Productivity Productivity =(units of output) (resources input) But what is the unit of output?  Size related measures lines of code (what is a line?)  Function related measures e.g., UML nodes and arcs

  7. Team Productivity  Staff ability and expertise  Domain expertise  Process quality  Project size  Technology support  Working environment Microsoft is the world's greatest software company, but Windows 2000 is two years behind schedule.

  8. Cost Estimation Techniques The following techniques have been suggested. See Sommerville for details  Algorithmic cost modeling  Expert judgment  Estimation by analog  Parkinson's Law / pricing to win All these methods work reasonably in familiar domains. None work well in strange domains.

  9. Algorithmic Cost Estimation Factors to take into account:  Complexity  Computer attributes (e.g., embedded, networked)  Product metric (size or functionality)  Personnel attributes (e.g., experience, ability)

  10. Quality Management "Total Quality Management": A management fad of the early 1990s. Buzz words, consultants, books, training programs, awards, standards. But some good concepts:  Customer satisfaction, not internal measures  Staff development and participation in management (e.g., US Navy)  Continuous improvement of processes  Measurements and comparison with other industries

  11. Quality in Software Emphasis has been on:  process standards e.g., documentation standards  software process metrics Very valuable within organizations. Little success across organizations.

  12. Software with Monitoring Software can measure aspects of its use and performance:  Networking and distributed computing Example: SNMP  Monitoring user interfaces Which features are never used?  Logging and data mining

  13. Process Improvement Processes: project management, scheduling, communications, documentation, testing, reporting, recruiting, training, etc.  Understand the existing processes and practices actual practice may differ from official  Decide the appropriate level of processes big project => more process inexperienced team => more process  Improve and consolidate one step at a time acceptance => leadership

  14. Software Engineering Institute Process Maturity Model Categorization of contractors for DoD software: 1. Initial -- no effective management processes 2. Repeatable -- requirements management, project planning, scheduling and tracking, quality assurance, configuration control 3. Defined -- conformity to defined processes, design and code reviews, communication procedures, personnel development 4. Managed -- software quality management, quantitative process management 5. Optimizing -- continuous improvement of processes

  15. Software Processes How important are processes to the development of good software?

  16. Software Processes and Good Software  Processes do not guarantee good software ... but they help  Larger projects need more formality of management  There is no consensus about preferred processes  The keys to success are: high-quality professional staff good leadership realistic goals communication with client

  17. Software Reuse Potential benefits of reuse:Better software at lower cost  Reduce development time and cost  Improved reliability of mature components  Shared maintenance cost Potential disadvantages of reuse:  Difficulty in finding appropriate components  Components may be a poor fit for application

  18. Software Reuse Examples Software developers rely heavily on software components provided by others System software  device drivers  file systems  exception handling  task management  network protocols Database management systems

  19. Software Reuse Examples (Tools) Standard functions  mathematical methods  formatting User interface toolkits (e.g., Macintosh)  Graphics tools (Quickdraw)  Dialogs  WIMP -- windows, icons, menus, mouse tracking

  20. Software Reuse (Application Packages)  Package supports a standard application (e.g., payroll, user interface to Internet information)  Functionality can be enhanced by: => configuration parameters (e.g., table driven) => extensibility at defined interfaces => custom written sources code extensions

  21. Extensibility in Web Browsers  Data types: helper applications, plug-ins  Protocols HTTP, WAIS, Gopher, FTP, etc. proxies  Executable code CGI scripts at server JavaScript at client Java applets  Style sheets

  22. Reuse and Object Object Oriented Languages Example: Java is a relatively straightforward language with a very rich set of class hierarchies.  Java programs derive much of their functionality from standard classes  Learning and understanding the classes is difficult.  Java experts can write complex systems quickly  Inexperienced Java programmers write inelegant and buggy programs

  23. Reading Before next class, read Sommerville Chapters 17, pages 319 to 346