1-SoftwareEngineeringandBestPractices.ppt
- 1. 30 Software Engineering and Best Practices Sources: Various. Rational Software Corporation slides, OOSE textbook slides, Per Kroll talk, How to Fail with the RUP article, textbooks Most slides have been modified considerably
- 2. 30 2 Fundamental Terms / Concepts ►Science and Engineering Discover ►Relationships that exist but are not found ►Formulas; chemical composition, d=r*t; calories in fats, carbohydrates, proteins; experimentation; ►Astrophysics – origins of the universe Build ►Apply principles of science and mathematics to real needs, commodities, structures, products, etc. ►Software Engineering; Software Development
- 3. 30 3 Fundamental Concepts / Terms (2) ►Software Engineering; Software Development ►Job positions: Software developer Programmer Software engineer Analyst / Programmer Senior … what have you…
- 4. 30 4 What is Software Engineering? ►The process of solving customers’ problems by the systematic development and evolution of large, high-quality software systems within cost, time and other constraints ►Note: Process, systematic (not ad hoc), evolutionary… Constraints: high quality, cost, time, meets user requirements
- 5. 30 5 Analysis of the Definition: ► Systematic development and evolution An engineering process involves applying well understood techniques in a organized and disciplined way Many well-accepted practices have been formally standardized ► e.g. by the IEEE or ISO Most development work is evolutionary ► Large, high quality software systems Software engineering techniques are needed because large systems cannot be completely understood by one person Teamwork and co-ordination are required Key challenge: Dividing up the work and ensuring that the parts of the system work properly together The end-product that is produced must be of sufficient quality ► Cost, time and other constraints Finite resources The benefit must outweigh the cost Others are competing to do the job cheaper and faster Inaccurate estimates of cost and time have caused many project failures
- 6. 30 6 Comments: ► $250 billion annually in US. ► Over 175,000 projects! ► Complexity, size, distribution, importance push our limits. ► Business pushes these limits: Great demands for rapid development and deployment ► Incredible pressure: develop systems that are: On time, Within budget, Meets the users’ requirements ► Figures in the late 90s indicated that at most 70% of projects completed Over 50% ran over twice the intended budget $81 billion dollars spent in cancelled projects!! ► Getting better, but we need better tools and techniques!
- 7. 30 7 What Happens in Practice Sequential activities: (Traditional ‘Waterfall’ Process) Requirements Design Code Integration Test Late Design Breakage 100% Project Schedule Development Progress (% coded) Original Target Date Integration Begins Risk inadequately addressed Process not receptive to Change Problems not really ‘seen’ until near delivery date! Until then, ‘all is well…’ Big Bang approach – full delivery Long development cycles… Little user involvement, etc. etc…
- 8. 30 8 Symptoms of Software Development Problems ► Inaccurate understanding of end-user needs ► Inability to deal with changing requirements ► Modules that don’t fit together (integration) ► Software that’s hard to maintain or extend (brittle) ► Late discovery of serious project flaws (integration) ► Poor software quality (architecture, risks unanticipated…) ► Process not responsive to Change (Gantt Charts…) ► Unacceptable software performance ► Team members in each other’s way, unable to reconstruct who changed what, when, where, why (software architecture, … ► …and we could go on and on…
- 9. 30 9 ► We need a process that Will serve as a framework for large scale and small projects Adaptive – embraces ‘change!’ ►Opportunity for improvement not identification of failure! Iterative (small, incremental ‘deliverables’) Risk-driven (identify / resolve risks up front) Flexible, customizable process (not a burden; adaptive to projects) Architecture-centric (breaks components into ‘layers’ or common areas of responsibility…) Heavy user involvement ► Identify best ways of doing things – a better process – acknowledged by world leaders… Need a Better Hammer!
- 10. 30 10 Develop Iteratively Control Changes Use Component Architectures Manage Requirements Model Visually Verify Quality Best Practices of Software Engineering Know these!
- 11. 30 11 Symptoms end-user needs changing requirements modules don’t fit hard to maintain late discovery poor quality poor performance colliding developers build-and-release Root Causes insufficient requirements ambiguous communications brittle architectures overwhelming complexity undetected inconsistencies poor testing subjective assessment waterfall development uncontrolled change insufficient automation Best Practices develop iteratively manage requirements use component architectures model the software visually verify quality control changes Addressing Root Causes Eliminates the Symptoms Symptoms of problems can be traced to having Root Causes. Best Practices are ‘practices’ designed to address the root causes of software problems.
- 12. 30 12 Practice 1: Develop Software Iteratively Develop Iteratively Control Changes Use Component Architectures Manage Requirements Model Visually Verify Quality Considered by many practitioners to be the most significant of the six
- 13. 30 13 Practice 1: Develop Software Iteratively ►Until recently, developed under assumption - most requirements can be identified up front. ►The research deconstructing this myth includes work by Capers Jones. (See next slide) In this very large study of 6,700 projects, creeping requirements — those not anticipated near the start—are a very significant fact of software development life, ranging from around 25% on average projects up to 50% on larger ones.
- 14. 30 14 Look up a definition of ‘Function Points.’
- 15. 30 15 Interestingly, ► An initial design will likely be flawed with respect to its key requirements. Requirements rarely fully known up front! ► Late-phase discovery of design defects results in costly over-runs and/or project cancellation Oftentimes requirements change – even during implementation! ► While large projects are more prone to cost overruns, medium-size/small projects are vulnerable to cancellation. ► The key reasons continue to be poor project planning and management, shortage of technical and project management expertise, lack of technology infrastructure, disinterested senior management, and inappropriate project teams.”
- 16. 30 16 Waterfall Delays Risks R I S K T I M E Integration System Test Code Design Requirements Waterfall risk Walker Royce, 1995
- 17. 30 17 Iterative Development • Earliest iterations address greatest risks • Each iteration produces an executable release • Each iteration includes integration, test, and assessment! • Objective Milestones: short-term focus; short term successes! Iteration 1 Iteration 2 Iteration 3
- 18. 30 18 Accelerate Risk Reduction Iterative T I M E Iteration Iteration Iteration Iteration Iteration Risk reduction R I S K Waterfall risk Walker Royce, 1995
- 19. 30 19 Iterative Development Characteristics ► Critical risks are resolved before making large investments ► Initial iterations enable early user feedback Easy to resolve problems early. Encourages user feedback in meaningful ways ► Testing and integration are continuous – assures successful integration (parts all fit) Continuous testing. ► Objective milestones provide short-term focus ► Progress measured by assessing implementations ► Partial implementations can be deployed Waterfall method – no delivery Incremental development? May be some great values in delivering key parts of application. Critical components delivered first? ► No big-bang approach!
- 20. 30 20 UP Lifecycle Graph – Showing Iterations In an iteration, you may walk through all disciplines C O N T E N T S T R U C T U R E T I M E STUDY THIS!!!
- 21. 30 21 Executable Releases Unified Process Iterations and Phases An iteration is a distinct sequence of activities with an established plan and evaluation criteria, resulting in an ‘executable release.’ (There is a lot of very important ‘key’ terminology used here… (cycle, iteration, phase, milestones, core disciplines, content of iterations, etc….) Preliminary Iteration Architect. Iteration Architect. Iteration Devel. Iteration Devel. Iteration Devel. Iteration Transition Iteration Transition Iteration Elaboration Construction Transition Inception
- 22. 30 22 Enables and encourages user feedback Serious misunderstandings evident early in the life cycle Development focuses on critical issues – break it down! Objective assessment thru testing and assessment Inconsistencies detected early Testing starts earlier – continuous! Risks identified and addressed early - via planned iterations! Problems Addressed by Iterative Development Root Causes Solutions Insufficient requirements Ambiguous communications Brittle architectures Overwhelming complexity Subjective assessment Undetected inconsistencies Poor testing Waterfall development Uncontrolled change Insufficient automation
- 23. 30 23 No Free Lunch- Traps Abound… ► Major impacts on Project Managers, though…. ► Trap: When the initial risks are mitigated, new ones emerge Do not do just the easy stuff, to look good. Keep re-planning based on all new information. ► Trap: Remember ‘some’ Rework enables you to enhance your solution Accommodate change early in the project ► Trap: Iterative development does not mean never to commit to a solution ► Monitor ‘scrap and rework’ ► Trap: Must Control “requirement creep, ” however… Some clients will now naturally recognize many ‘musts…’
- 24. 30 24 Many Traps in Iterative Development Here is another trap: Too long initial iteration ► Winning is fun. Winning teams work better than loosing teams ► Better to have a short initial iteration, than one too long Cut scope if necessary (much more later) ► Avoid ‘analysis-paralysis’ by time-boxing; you can enhance in later iterations (more later) ► Establish an even rhythm for project (at least w/i a phase) ► Focus on results and deliverables, not activities
- 25. 30 25 Iterations Are Time-boxed ►Work is undertaken within an iteration. ►The iteration plan defines the artifacts to be delivered, roles and activities. ►An iteration is clearly measurable. ►Iterations are risk-driven ►Iterations are planned. ►Iterations are assessed! ►Generally, initial iterations (in Construction) based on high risk and core functionalities!
- 26. 30 26 The Iteration Plan Defines…. The deliverables for that iteration. The to do list for the team members artifacts
- 27. 30 27 Problem: Fixed Plans Produced Upfront – Not Real Practical! ►Yet, senior management wants firm, fixed plans! Part of their culture / upbringing/ experience Necessary for ‘planning’ budgeting, etc. of resources, projects…. BUT: ►Trap: Fine-grained planning from start to end? Takes too much time Frustrating as change occurs (and it will), if plans too fine-grained. ►Know that: Projects typically have some degree of uncertainty ►This makes detailed plans for the entire project meaningless ►Does not mean that we should not plan
- 28. 30 28 Solution: Plan With Evolving Levels of Detail Current Iteration Next Iteration Phases and major milestones What and when Iterations for each phase Number of iterations Objectives and Duration One For Entire Project Fine-grained Plans: Iteration Plans Coarse-grained Plan: Software Development Plan Iterative Development does not mean less work and shorter schedule It is about greater predictability
- 29. 30 29 Progress is made against MILESTONES ►In the Unified Process: Each phase is defined by a milestone. Progress is made by passing milestones. Milestones measure success ►Phases - NOT TIMEBOXED. ►Iterations ARE TIMEBOXED. Inception Elaboration Construction Transition Major Milestones
- 30. 30 30 Summary ►Much more about iteration and iteration planning later in the course… ►You will see some of these again – and, more importantly, use this information in your own iteration planning.