The Software Process ECE 417/617: Elements of Software Engineering Stan Birchfield Clemson University

Life cycle phases 5 phases of every S/W life cycle: Communication – requirements gathering, project initiation Planning – determine tasks, risks, resources, work products, schedule; estimate, schedule, track Modeling – create models to facilitate more precise communication and planning; includes analysis and design Construction – code generation and testing Deployment – delivery, feedback, support Two approaches: prescriptive and agile

Waterfall model [adapted from Royce (1970)] Requirements Analysis System Design Object Design Coding Testing Installation Maintenance [adapted from Royce (1970)]

What is wrong with waterfall? Requirements Analysis Maintenance System Design Installation Object Design Testing Coding Interrelated  nonlinear, sequential

V-model is validated by less detail more detail build system Requirements Analysis Acceptance Testing is validated by less detail System Design System Testing Object Design Unit Testing more detail Coding build system validate system

Incremental model features time increment #3 version #3 increment #2 #1 A D C T M time

Rapid application development (RAD) Team #1 Modeling Communication Construction Planning Deployment Team #N Modeling Construction Developed by James Martin at IBM in 1980s RAD has largely been discredited because it has not proved successful "RAD is back", says IBM, Information Age, Feb. 10, 2006 http://www.information-age.com/articles/296861/rad-is-back-says-ibm.thtml 60 – 90 days

Prototyping Enables faster feedback Communication Feedback Quick plan Delivery Quick modeling Construct Prototype Enables faster feedback Can be incorporated into other models But what is the danger?

Shark tooth model [from Michael Black]

Spiral model “Risk-driven approach” Deployment Communication start Construction Planning Modeling “Risk-driven approach” [developed by Barry Boehm, 1988]

Concurrent Each activity can be in a different state: none under development awaiting changes under review under revision baselined done

Unified process inception elaboration transition construction software increment inception Communication Deployment Planning transition elaboration Construction Modeling construction Incremental, iterative “Unified”  same originators as UML Also called Rational Unified Process (RUP) Based on spiral model, developed at Rational Software, a division of IBM since 2003

Unified process work products Inception phase vision document initial use-case model initial business case initial risk list project plan prototype(s) ... Elaboration phase use-case model requirements analysis model preliminary model revised risk list preliminary manual ... Construction phase design model SW components test plan test procedure test cases user manual installation manual ... Transition phase SW increment beta test reports user feedback ...

Agile development S/W development is unpredictable requirements will change (which ones?) design and construction are interleaved (how much design is needed?) analysis and testing, too Solution: Use an adaptable process incremental development strategy

Agile principles Agile Manifesto (2001) values Agile principles: individuals and interactions over processes and tools working software over comprehensive documentation customer collaboration over contract negotiation responding to change over following a plan Agile principles: satisfy customer (highest priority) early and frequent S/W delivery welcome changing requirements work daily with business people and developers build projects around motivated individuals simplicity: maximize the amount of work NOT done self-organizing teams regular reflection to adjust behavior to improve effectiveness

Extreme programming (XP) Kent Beck became project leader of Chrysler’s payroll project in 1996 Project canceled in 2000 [Kent Beck, Extreme Programming Explained, 1999] [from extremeprogramming.org]

A simpler view of XP design planning coding test spike solutions (prototypes) CRC cards design planning coding refactoring test unit test acceptance test continuous integration S/W increment

XP principles Pros and cons? Test-driven development The planning game On-site customer Pair programming Continuous integration Refactoring Small releases Simple design System metaphor Collective code ownership Coding standards 40-hour work week Pros and cons?

Adaptive S/W development (ASD) ASD focuses on human collaboration and team self-organization collaboration speculation learning S/W increment [Highsmith 2000]

Scrum Backlog – prioritized list of project requirements or features Sprints – work units required to achieve a requirement deliver within fixed time (30 days) no changes to requirement allowed during that time Daily meetings (15 min.) What did you do? What obstacles are you encountering? What is your plan? Demos – S/W increments delivered to customer (can ship final product upon demand)

BDUF controversy BDUF – Big design up front Proponents claim that planning up front saves lots of time in the end Much faster to fix a bug in the spec than in the code An ounce of prevention is worth a pound of cure Who is right? Both. Strive for balance.

Model summary Prescriptive models Waterfall Incremental RAD Spiral Concurrent development Component-based development Formal methods Aspect oriented Unified process (RUP) Agile models Extreme programming (XP) Adaptive software development (ASD) Dynamic systems development (DSDM) Scrum Crystal Feature driven development (FDD) Agile model

Synch-and-stabilize How to balance structure and flexibility? Solution: Plan product with vision statement Translate into specification document with enough detail to divide the work Divide into parts and assign to teams Teams are free to implement, innovate as they wish Teams work under common environment Teams check-in work frequently Frequent (daily) builds Always a working system Easy to test, see defects, measure progress continually [from “How Microsoft Builds Software”, Cusumano and Selby]

Personal software process (PSP) Individual developers should measure the quality of output plan (estimate and schedule work) identify likely and actual errors use metrics to improve process Activities: (1) planning, (2) high-level design, (3) high-level design review, (4) development, (5) postmortem Disciplined metrics-based approach to software engineering Requires significant training Improves productivity and quality, but resisted by many developers (culture shock) [SEI’s Watts Humphreys]

Team software process (TSP) Project team should be self-directed, able to plan and track their work, establish goals, and own their processes and plans have consistent understanding of its overall goals and objectives define roles and responsibilities track quantitative project data identify and implement an appropriate process for the project define local standards continually assess and respond to risks track, manage, and report project status Activities: (1) launch, (2) high-level design, (3) implementation, (4) integration and test, (5) postmortem Rigorous approach that requires a full commitment from the team Requires thorough training Improves productivity and quality [SEI’s Watts Humphreys]