September 3, 2008 Lecture 4 1CS 390 – Lecture 4Other Software Life Cycle ModelsCode-and-fix life-cycle modelWaterfall life-cycle modelRapid prototyping life-cycle modelOpen-source life-cycle modelAgile processesSynchronize-and-stabilize life-cycle modelSpiral life-cycle modelSeptember 3, 2008 Lecture 4 2Code-and-Fix Model (Figure 2.8)No designNo specifi-cationsMaintenance nightmareThe easiest way to develop softwareThe most expensive waySeptember 3, 2008 Lecture 4 3Full Waterfall Model (Figure 2.9)Characterized byFeedback loopsDocumentation-drivenAdvantages DocumentationMaintenance is easier DisadvantagesSpecification documentSeptember 3, 2008 Lecture 4 4Rapid Prototyping Model (Figure 2.10)Linear modelAnalysis after prototype“Rapid”September 3, 2008 Lecture 4 5Open-Source Life-Cycle ModelTwo informal phases. First, one individual builds an initial versionMade available via the Internet (e.g., SourceForge.net) Then, if there is sufficient interest in the projectThe initial version is widely downloadedUsers become co-developersThe product is extendedKey point: Individuals generally work voluntarily on an open-source project mostly in their spare timeSeptember 3, 2008 Lecture 4 6Open-Source Life-Cycle Model (2)In the second informal phase, report and correct defectsCorrective maintenanceAdd additional functionalityPerfective maintenancePort the program to a new environmentAdaptive maintenanceThis phase consists solely of postdelivery maintenanceThe word “co-developers” on the previous slide really should be “co-maintainers”September 3, 2008 Lecture 4 7Open-Source Life-Cycle Model (3)Could be called the postdelivery maintenance life-cycle model (Figure 2.11)September 3, 2008 Lecture 4 8Compare Open-Source Life-Cycle with Closed-Source SoftwareClosed-source software is maintained and tested by employeesUsers can submit failure reports but never fault reports (the source code is not available)Open-source software is generally maintained by unpaid volunteersUsers are strongly encouraged to submit defect reports, both failure reports and fault reportsSeptember 3, 2008 Lecture 4 9Compare Open-Source Life-Cycle with Closed-Source Software (2)Two types of maintainers. Core groupSmall number of dedicated maintainers with the inclination, the time, and the necessary skills to submit fault reports (“fixes”)They take responsibility for managing the projectThey have the authority to install fixesPeripheral groupUsers who choose to submit defect reports from time to time September 3, 2008 Lecture 4 10Compare Open-Source Life-Cycle with Closed-Source Software (3)New versions of closed-source software are typically released roughly once a yearAfter careful testing by the SQA groupThe core group releases a new version of an open-source product as soon as it is readyPerhaps a month or even a day after the previous version was releasedThe core group performs minimal testingExtensive testing is performed by the members of the peripheral group in the course of utilizing the software“Release early and often”September 3, 2008 Lecture 4 11Open-Source Life-Cycle Model (4)An initial working version is produced when usingThe rapid-prototyping model;The code-and-fix model; and The open-source life-cycle modelThen:Rapid-prototyping modelThe initial version is discardedCode-and-fix model and open-source life-cycle modelThe initial version becomes the target productSeptember 3, 2008 Lecture 4 12Open-Source Life-Cycle Model (5)Consequently, in an open-source project, there are generally no specifications and no designHow have some open-source projects been so successful without specifications or designs?September 3, 2008 Lecture 4 13Open-Source Life-Cycle Model (6)Open-source software production has attracted some of the world’s finest software expertsThey can function effectively without specifications or designsHowever, eventually a point will be reached when the open-source product is no longer maintainableSeptember 3, 2008 Lecture 4 14Open-Source Life-Cycle Model (7)The open-source life-cycle model is restricted in its applicabilityIt can be extremely successful for infrastructure projects, such as Operating systems (Linux, OpenBSD, Mach, Darwin)Web browsers (Firefox, Netscape)Compilers (gcc)Web servers (Apache)Database management systems (MySQL)September 3, 2008 Lecture 4 15Open-Source Life-Cycle Model (8)There cannot be open-source development of a software product to be used in just one commercial organizationMembers of both the core group and the periphery are invariably users of the software being developedThe open-source life-cycle model is inapplicable unless the target product is viewed by a wide range of users as useful to themSeptember 3, 2008 Lecture 4 16Open-Source Life-Cycle Model (9)About half of the open-source projects on the Web have not attracted a team to work on the projectEven where work has started, the overwhelming preponderance will never be completedBut when the open-source model has worked, it has sometimes been incredibly successfulThe open-source products previously listed have been utilized on a regular basis by millions of usersSeptember 3, 2008 Lecture 4 17Extreme Programming (XP)Somewhat controversial new approachStories (features client wants)Estimate duration and cost of each storyClient selects stories for next buildEach build is divided into tasksTest cases for a task are drawn up firstPair programmingContinuous integration of tasksSeptember 3, 2008 Lecture 4 18Unusual Features of XPThe computers are put in the center of a large room lined with cubiclesA client representative is always presentSoftware professionals cannot work overtime for 2 successive weeksNo specializationRefactoring (design modification)September 3, 2008 Lecture 4 19Agile ProcessesXP is one of a number of new paradigms collectively referred to as agile processesSeventeen software developers (later dubbed the “Agile Alliance”) met at a Utah ski resort for two days in February 2001 and produced the Manifesto for Agile Software Development The Agile Alliance did not prescribe a specific life-cycle modelInstead, they laid out a group of underlying principlesSeptember 3, 2008