Chapter 1 Conventional Software Management.ppt

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1、Chapter 1 Conventional Software Management,Introduction,Three analyses of the state of the software engineering industry as of mid 1990s yielded: Software Development is still highly unpredictable Only about 10% of software projects are delivered successfully on time, within initial budget, and meet

2、s user requirements The management discipline is more of a discriminator in success or failure than are technology advances The level of software scrap and rework is indicative of an immature process. Behold the magnitude of the software problem and current norms! But is the theory bad? “Practice ba

3、d?” Both? Lets consider.,I. The Waterfall Model,Recognize that there are numerous variations of the waterfall model. Tailored to many diverse environments The theory behind the waterfall model good Oftentimes ignored in the practice The practice some good; some poor,Waterfall Theory Historical Persp

4、ective and Update,Circa 1970: lessons learned and observations Point 1: There are two essential steps common to the development of computer programs: analysis and coding - More later on this one.Point 2: In order to manage and control all of the intellectual freedom associated with software developm

5、ent, one must introduce several other overhead steps, including system requirements definition, software requirements definition, program design, and testing. These steps supplement the analysis and coding steps.” (See Fig 1-1, text, p. 7, which model basic programming steps and large-scale approach

6、)Point 3: The basic framework is risky and invites failure. The testing phases that occurs at the end of the development cycle is the first event for which timing, storage, input/output transfers, etc. are experienced as distinguished from analyzed. The resulting design changes are likely to be so d

7、isruptive that the software requirements upon which the design is based are likely violated. Either the requirements must be modified or a substantial design change is warranted. Discuss.,Waterfall Theory Suggested Changes Then and Now,1. “Program design” comes first. Occurs between SRS generation a

8、nd analysis. Program designer looks at storage, timing, data. Very high levelFirst glimpse. First concepts During analysis: program designer must then impose storage, timing, and operational constraints to determine consequences. Begin design process with program designers, not analysts and programm

9、ers Design, define, and allocate data processing modes even if wrong. (allocate functions, database design, interfacing, processing modes, i/o processing, operating procedures. Even if wrong!) Build an overview document to gain a basic understanding of system for all stakeholders.,Waterfall Theory S

10、uggested Changes Then and Now,Point 1: Update: We use the term architecture first development rather than program design. Elaborate: distribution, layered architectures, components Nowadays, the basic architecture MUST come first. Recall the RUP: use-case driven, architecture-centric, iterative deve

11、lopment process Architecture comes first; then it is designed and developed in parallel with planning and requirements definition. Recall RUP Workflow diagrams.,Waterfall Theory Suggested Changes Then and Now,Point 2: Document the Design Development efforts required huge amounts of documentation man

12、uals for everything User manuals; operation manuals, program maintenance manuals, staff user manuals, test manuals Most of us would like to ignore documentation. Each designer MUST communicate with various stakeholders: interface designers, managers, customers, testers, developers, ,Waterfall Theory

13、 Suggested Changes Then and Now,Point 2: Update: Document the Design Now, we concentrate primarily on artifacts those models produced as a result of developing an architecture, performing analysis, capturing requirements, and deriving a design solution Include Use Cases, static models (class diagram

14、s, state diagrams, activity diagrams), dynamic models (sequence and collaboration diagrams), domain models, glossaries, supplementary specifications (constraints, operational environmental constraints, distribution, .) Modern tools / notations, and methods produce self-documenting artifacts from dev

15、elopment activities. Visual modeling provides considerable documentation,Waterfall Theory Suggested Changes Then and Now,Point 3: Do it twice. History argues that the delivered version is really version #2. Microcosm of software development. Version 1, major problems and alternatives are addressed t

16、he big cookies such as communications, interfacing, data modeling, platforms, operational constraints, other constraints. Plan to throw first version away sometimes Version 2, is a refinement of version 1 where the major requirements are implemented. Version 1 often austere; Version 2 addressed shor

17、tcomings! Point 3: Update. This approach is a precursor to architecture-first development (see RUP). Initial engineering is done. Forms the basis for iterative development and addressing risk!,Waterfall Theory Suggested Changes Then and Now,Point 4: Then: Plan, Control, and Monitor Testing. Largest

18、consumer of project resources (manpower, computing time, ) is the test phase. Phase of greatest risk in terms of cost and schedule. (EST 1) Occurs last, when alternatives are least available, and expenses are at a maximum. Typically that phase that is shortchanged the most To do: 1. Employ a non-ves

19、ted team of test specialists not responsible for original design. 2. Employ visual inspections to spot obvious errors (code reviews, other technical reviews and interfaces) 3. Test every logic path 4. Employ final checkout on target computer,Waterfall Theory Suggested Changes Then and Now,Point 4: N

20、ow: Plan, Control, and Monitor Testing. Items 1 and 4 are still valid. 1) Use a test team not involved in the development of the system at least for testing other than unit testing 4) Employ final checkout on target computer. Item 2 (software inspections) good years ago, but modern development envir

21、onments obviate this need. Many code analyzers, optimizing compilers, static and dynamic analyzers are available to automatically assist May still yield good results but not for significant problems! Stylistic! Item 3 (testing every path) is impossible. Very difficult with distributed systems, reusa

22、ble components (necessary?), and other factors. (aspects),Waterfall Theory Suggested Changes Then and Now,Point 5 Old: Involve the Customer Old advice: involve customer in requirements definition, preliminary software review, preliminary program design (critical design review briefings) Now: Involvi

23、ng the customer and all stakeholders is critical to overall project success. Demonstrate increments; solicit feedback; embrace change; cyclic and iterative and evolving software. Address risk early,Overall Appraisal of Waterfall Model,Criticism of the waterfall model is misplaced. Theory is fine. Pr

24、actice is what was poor!,But: Less than 20% success rate,The Software Development Plan: Old Version,Define precise requirements Define precise plan to deliver systemConstrained by specified time and budget Execute and track to plan,Stakeholder Satisfaction Space,Initial Project SituationReused or le

25、gacy assetsDetailed plans, scope,1.1.2 In Practice,Characteristics of Conventional Process as it has been applied (in general) Projects not delivered on-time, not within initial budget, and rarely met user requirements Projects frequently had: 1. Protracted integration and late design breakage 2. La

26、te risk resolution 3. Requirements-driven functional decomposition 4. Adversarial stakeholder relationships 5. Focus on documents and review meetings Lets look at these five major problems,Sequential Activities: Requirements Design Code Integration,100%,Project Schedule,Development Progress (% coded

27、),Original Target Date,Completion Date,. Early paper designs and thorough briefings . Commitment to code very late in cycle . Integration nightmares due to unforeseenimplementation and interface issues . Heavy budget and schedule pressure . Late shoe-horning of non-optimal fixeswith no time for rede

28、sign! . A very fragile, un-maintainable product and almost always: delivered late.,1. Protracted Integration and Late Design Breakage,Expenditures per activity for a Conventional Software Project,Activity Cost Management 5% Requirements 5% Design 10% Code and unit test 30% Integration and Test 40% D

29、eployment 5% Environment 5%Total 100% Lots of time spent on perfecting the software design prior to commitment to code. Typically had: requirements in English, design in flowcharts, detailed design in pdl, and implementations in Fortran, Cobol, or C Waterfall model late integration and performance s

30、howstoppers. Could only perform testing at the end (other than unit testing) Testing should have required 40% of life-cycle resources: often didnt!,2. Late Risk Resolution,Problem here: focused on early paper artifacts. Real issues still unknown and hard to grasp.Difficult to resolve risk during req

31、uirements when many key items still not fully understood. Even in design, when requirements better understood, still difficult to get objective assessment. Risks were at a very high level During coding, some risks resolved, BUT during Integration, many risks were quite clear and changes to many arti

32、facts and retrenchment often had to occur While much retrenchment did occur, it often caused missed dates, delayed requirement compliance, or, at a minimum, sacrificed quality (extensibility, maintainability, loss of original design integrity, and more). Quick fixes, often without documentation occu

33、rred a lot!,3. Requirements-Driven Functional Decomposition,Traditionally, software development processes have been requirements-driven. Developers: assumed requirement specs: complete, clear, necessary, feasible, and remaining constant! This is RARELY the case! All too often, too much time spent on

34、 equally treating all requirements rather than on critical ones. Much time spent on documentation on topics (traceability, testability, etc.) that was later made obsolete as DRIVING REQUIREMENTS AND SUBSEQUENT DESIGN UNDERSTANDING EVOLVE. We do not KNOW all wed like to know up front. Too much time a

35、ddressing all of the scripted requirements normally listed in tables, decision-logic tables, flowcharts, and plain, old text. Much brainpower wasted on the lesser requirements. Also, assumption that all requirements could be captured as functions and resulting decomposition of these functions. Funct

36、ions, sub-functions, etc. became the basis for contracts and work apportionment, while ignoring major architectural-driven approaches and requirements that are threaded throughout functions and that transcend individual functions. (security; authentication; persistency; performance) Fallacy: all req

37、uirements can be completely specified up front and (and decomposed) via functions.,4. Adversarial Stakeholder Relationships (1 of 2),Who are stakeholders? Discuss.Quite a diverse group! Adversarial relationships OFTEN true! Misunderstanding of documentation usually written in English and with busine

38、ss jargon. Paper transmission of requirements only method used. No real modeling, universally-agreed-to languages with common notations; (no GUIs, network components already available; Most systems were custom.) Subjective reviews / opinions. Generally without value! more Management Reviews; Technic

39、al Reviews!,Adversarial Stakeholder Relationships Common Occurrences:,Common events with contractual software: 1. Contractor prepared a draft contract-deliverable document that constituted an intermediate artifact and delivered it to the customer for approval. (usually done after interviews, questio

40、nnaires, meetings) 2. Customer was expected to provide comments (typically within 15-30 days.) 3. Contractor incorporated these comments and submitted (typically 15-30 days) a final version for approval. Evaluation: Overhead of paper was huge and intolerable. Volumes of paper! (often under-read) Str

41、ained contractor/customer relationships Mutual distrust basis for much litigation Often, once approved, rendered obsolete later.(living document?),5. Focus on Documents and Review Meetings,A very documentation-intensive approach. Insufficient attention on producing credible increments of the desired

42、 products. Big bang approach all FDs delivered at once; All Design Specs okd at once and briefed Milestones commemorated via review meetings technical, managerial, Everyone nodding and smiling often Incredible energies expended on producing paper documentation to show progress versus efforts to addr

43、ess real risk issues and integration issues. Stakeholders often did not go through design Very VERY low value in meetings and high costs Travel, accommodations Many issues could have been averted early during development during early life-cycle phases rather than encountered huge problems late.but,C

44、ontinuing. Typical Software product design Reviews.,1. Big briefing to a diverse audience Results: only a small percentage of the audience understands the software Briefings and documents expose few of the important assets and risks of complex software. 2. A design that appears to be compliant There

45、 is no tangible evidence of compliance Compliance with ambiguous requirements is of little value. 3. Coverage of requirements (typically hundreds.) Few (tens) are in reality the real design drivers, but many presented Dealing with all requirements dilutes the focus on critical drivers. 4. A design c

46、onsidered innocent until proven guilty The design is always guilty Design flaws are exposed later in the life cycle.,1.2 Conventional Software Management Performance,Very few changes from Barry Boehms “industrial software metrics” from 1987. Most still generally describe some of the fundamental econ

47、omic relationships that are derived from years of practice: What follows is Barrys top ten (and your authors (and my) comments.,Basic Software Economics,1. Finding and fixing a software problem after delivery costs 100 times more than fining and fixing the problem in early design phases. Flat true.

48、2. You can compress software development schedules 25% of nominal, but no more.Addition of people requires more management overhead and training of people. Still a good heuristic. Some compression is sometimes possible! Be careful! Oftentimes it is a killer to add people.(Discuss later) 3. For every

49、 dollar you spend on development, you will spend two dollars on maintenance. We HOPE this is true! Hope so. Long life cycles mean revenueStill, hard to tell Products success in market place is driver. Successful products will have much higher ratios of “maintenance to development” One of a kind development will most likely NOT spend this kind of money on maintenance . Examples: implementation / conversion subsystems Conversion software.,