1. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 1 Software Projects You need to deliver the following things: Project Agreement (already completed)Project Agreement (already completed) DocumentationDocumentation CodeCode Demonstration for ClientDemonstration for Client Presentation in ClassPresentation in Class

2. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 2 Software Projects Documentation: Describes the capabilities of the software productDescribes the capabilities of the software product Explains to the end user how to use the softwareExplains to the end user how to use the software Describes to other developers the most important classes, their members and methods.Describes to other developers the most important classes, their members and methods. Due by May 14.Due by May 14. It is recommended to write at least a rough draft of the documentation before writing the code.It is recommended to write at least a rough draft of the documentation before writing the code.

3. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 3 Software Projects Code: Programming language: C++Programming language: C++ Operating system: Linux (software must be demonstrated on campus)Operating system: Linux (software must be demonstrated on campus) Object-oriented designObject-oriented design CommentsComments Due by May 14 (e-mail)Due by May 14 (e-mail)

4. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 4 Software Projects Demonstration for Client: Demonstration in Unix Lab, PC Lab, Visual Attention Lab or client’s officeDemonstration in Unix Lab, PC Lab, Visual Attention Lab or client’s office Can be done on a team member’s laptopCan be done on a team member’s laptop Customer will play around with the software and try to crash itCustomer will play around with the software and try to crash it Code review: Every project participant will be asked questions about her/his code and why she/he chose that particular implementation.Code review: Every project participant will be asked questions about her/his code and why she/he chose that particular implementation. Due by May 14Due by May 14

5. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 5 Software Projects Presentation in Class: Duration for each team’s presentation: 20 minutesDuration for each team’s presentation: 20 minutes Every team member has to speakEvery team member has to speak One person (team leader) provides overview of the systemOne person (team leader) provides overview of the system Others present their part of the system, algorithms and data structures they used, issues they encountered, how they were resolved, etc.Others present their part of the system, algorithms and data structures they used, issues they encountered, how they were resolved, etc. Will take place on May 1, 6, and 8.Will take place on May 1, 6, and 8.

6. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 6 Software Projects Rules: Each team member must implement a clearly defined part of the software.Each team member must implement a clearly defined part of the software. No re-use of any code unless explicitly allowed by the customer.No re-use of any code unless explicitly allowed by the customer. It is recommended to schedule at least one meeting with the customer during the development process.It is recommended to schedule at least one meeting with the customer during the development process. Team members will evaluate each other after project completion.Team members will evaluate each other after project completion.

7. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 7 Rationale Management Rationale: What is it?What is it? Why should you care?Why should you care? Rationale methods: Representing rationaleRepresenting rationale Authoring rationaleAuthoring rationale Accessing rationaleAccessing rationale State of practice & research Summary

8. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 8 An Aircraft Example A320: First fly-by-wire passenger aircraftFirst fly-by-wire passenger aircraft 150 seats, short to medium haul150 seats, short to medium haul A319 & A321: Derivatives of A320Derivatives of A320 Same handling as A320Same handling as A320Rationale: Reduce pilot training & maintenance costsReduce pilot training & maintenance costs Increase flexibility for airlineIncrease flexibility for airline

9. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 9 An Aircraft Example A330 & A340: Long haul and ultra long haulLong haul and ultra long haul 2x seats, 3x range2x seats, 3x range Similar handling as A320 familySimilar handling as A320 familyRationale: With minimum cross training, A320 pilots can be certified to fly A330 and A340 airplanesWith minimum cross training, A320 pilots can be certified to fly A330 and A340 airplanesConsequence: Any change in these five airplanes must maintain this similarityAny change in these five airplanes must maintain this similarity

10. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 10 What is Rationale? Rationale is the reasoning that lead to the system. Rationale includes: Issues that were addressed, Alternatives that were considered, Decisions that were made to resolve the issues, Criteria that were used to guide decisions, and Debate developers went through to reach a decision.

11. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 11 Why Rationale? Software systems are similar to passenger airplanes: They result from a large number of decisions taken over an extended period of time. Evolving assumptions Evolving assumptions Legacy decisions Legacy decisions Conflicting criteria Conflicting criteria  High maintenance cost  Loss & rediscovery of information

12. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 12 Rationale Helps Deal with Change Improve maintenance support: Provide maintainers with design contextProvide maintainers with design context Improve learning: New staff can learn the design by replaying the decisions that produced itNew staff can learn the design by replaying the decisions that produced it Improve analysis and design: Avoid duplicate evaluation of poor alternativesAvoid duplicate evaluation of poor alternatives Make consistent and explicit trade-offMake consistent and explicit trade-off

13. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 13 Levels of Rationale No rationale captured: Rationale is only present in memos, online communication, developers’ memoryRationale is only present in memos, online communication, developers’ memory Rationale reconstruction: Rationale is documented in a document justifying the final designRationale is documented in a document justifying the final design Rationale capture: Rationale is documented during design as it is developedRationale is documented during design as it is developed Rationale integration: Rationale drives the designRationale drives the design

14. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 14 Example: Centralized Traffic Control CTC systems enable dispatchers to monitor and control trains remotely,CTC systems enable dispatchers to monitor and control trains remotely, CTC allows the planning of routes and re-planning in case of problems.CTC allows the planning of routes and re-planning in case of problems. T1291> <T1515 Track circuits Switches Trains Signals S1 S2 S3 SW1SW2 S4

15. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 15 Centralized Traffic Control CTC systems are ideal examples of rationale capture: Long lived systems (some systems include relays installed last century) Extended maintenance life cycleExtended maintenance life cycle Downtime is expensive (although not safety critical) Low tolerance for bugsLow tolerance for bugs Transition to mature technologyTransition to mature technology Initial developers are not available

16. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 16 input?:Issue display?:IssueIssues Issues are concrete problems which usually do not have a unique, correct solution.Issues are concrete problems which usually do not have a unique, correct solution. Issues are phrased as questions.Issues are phrased as questions. How should track sections be displayed? How should the dispatcher input commands?

17. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 17Proposals Proposals are possible alternatives to issues.Proposals are possible alternatives to issues. One proposal can be shared across multiple issues.One proposal can be shared across multiple issues. input?:Issuedisplay?:Issue addressed by text-based:Proposal addressed by point&click:Proposal The interface for the dispatcher could be realized with a point & click interface. The display used by the dispatcher can be a text only display with graphic characters to represent track segments.

18. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 18 Consequent Issues Consequent issues are issues raised by the introduction of a proposal.Consequent issues are issues raised by the introduction of a proposal. terminal?:Issue raises Which terminal emulation should be used for the display? input?:Issuedisplay?:Issue addressed by text-based:Proposal addressed by point&click:Proposal

19. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 19 Criteria A criterion represent a goodness measure.A criterion represent a goodness measure. Criteria are often design goals or nonfunctional requirements.Criteria are often design goals or nonfunctional requirements. availability$:Criterionusability$:Criterion fails The time to input commands should be less than two seconds. The CTC system should have at least a 99% availability. terminal?:Issue raises input?:Issuedisplay?:Issue addressed by text-based:Proposal addressed by point&click:Proposal meets

20. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 20Arguments Arguments represent the debate developers went through to arrive to resolve the issue.Arguments represent the debate developers went through to arrive to resolve the issue. Arguments can support or oppose any other part of the rationale.Arguments can support or oppose any other part of the rationale. Arguments constitute the largest part of the rationale.Arguments constitute the largest part of the rationale.

21. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 21Arguments availability-first!:Argumentis supported by is opposed by Point&click interfaces are more complex to implement than text-based interfaces. Hence, they are also more difficult to test. The point&click interface risks introducing fatal errors in the system that would offset any usability benefit the interface would provide. availability$:Criterionusability$:Criterion fails terminal?:Issue raises input?:Issuedisplay?:Issue addressed by text-based:Proposal addressed by point&click:Proposal meets

22. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 22Resolutions Resolutions represent decisions.Resolutions represent decisions. A resolution summarizes the selected alternative and the supporting argument.A resolution summarizes the selected alternative and the supporting argument. A resolved issue is said to be closed.A resolved issue is said to be closed. A resolved issue can be re-opened if necessary, in which case the resolution is demoted.A resolved issue can be re-opened if necessary, in which case the resolution is demoted.

23. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 23Resolutions text-based&keyboard :Resolution resolves availability-first!:Argument is supported by is opposed by availability$:Criterionusability$:Criterion fails terminal?:Issue raises input?:Issuedisplay?:Issue addressed by text-based:Proposal addressed by point&click:Proposal meets

24. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 24 Representing Rationale: Issue Models ProposalCriterion$ Issue? meets + fails - is a consequence responds Argument! supports + objects to - supports + objects to - Resolution. resolves

25. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 25 Representing Rationale Many issue models have been proposed: IBIS, QOC, DRL, WinWinIBIS, QOC, DRL, WinWin Similar in their essenceSimilar in their essence Differ in the amount of detail that can be capturedDiffer in the amount of detail that can be capturedChallenges: Require tool support for capture and accessRequire tool support for capture and access Require integration with project management toolsRequire integration with project management tools Require integration with methodologyRequire integration with methodology

26. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 26 Authoring Rationale Approaches: ReconstructionReconstruction Record-and-replayRecord-and-replay Byproduct of development methodologyByproduct of development methodologyChallenges: Lot of information to captureLot of information to capture Disruptive for developersDisruptive for developers Formalizing knowledge is expensiveFormalizing knowledge is expensive

27. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 27 Accessing Rationale Browse & search: Full text search allows to identify interesting nodesFull text search allows to identify interesting nodes Issue model links allow the browsing of related issues quicklyIssue model links allow the browsing of related issues quickly Passive & active design critique: Rationale can be used by knowledge based critiques to evaluate a designRationale can be used by knowledge based critiques to evaluate a designChallenges: Evolving terminologyEvolving terminology Navigation through a large flat spaceNavigation through a large flat space

28. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 28 State of the Practice Standalone issue based tools: QuestMapQuestMap Problem management tools: Work flow application tracking problems and resolutionsWork flow application tracking problems and resolutions Integrated with configuration managementIntegrated with configuration management Some tools (e.g., ClearQuest) allow schema to be customizedSome tools (e.g., ClearQuest) allow schema to be customizedRequisitePro: Requirements managementRequirements management Integrated with configuration managementIntegrated with configuration management Explicitly captures rationale behind changeExplicitly captures rationale behind change

29. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 29 An example of issue database (LN IBIS database template in Domino Lotus Notes).

30. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 30 State of Research Many solutions for representation exist and can be tailored to a specific problem. Progress in natural language search and in hypertext technology make access a less critical issue. Current challenges: Integration with methodologyIntegration with methodology Integration with toolsIntegration with tools OverheadOverhead

31. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 31 Open Issues Formalizing knowledge is costly: Maintaining a consistent design model is expensive.Maintaining a consistent design model is expensive. Capturing and maintaining its rationale is worse.Capturing and maintaining its rationale is worse. The benefits of rationale are not perceived by current developers: If the person who does the work is not the one who benefits from it, the work will have lower priority.If the person who does the work is not the one who benefits from it, the work will have lower priority. 40-90% of off-the-shelf software projects are terminated before the product ships.40-90% of off-the-shelf software projects are terminated before the product ships. Capturing rationale is usually disruptive. Current approaches do not scale to real problems.

32. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 32 Why Software Configuration Management? The problem: Multiple people have to work on software that is changingMultiple people have to work on software that is changing More than one version of the software has to be supported:More than one version of the software has to be supported:  Released systems  Custom configured systems (different functionality)  System(s) under development Software must run on different machines and operating systemsSoftware must run on different machines and operating systems Need for coordination Software Configuration Management manages evolving software systemsmanages evolving software systems controls the costs involved in making changes to a systemcontrols the costs involved in making changes to a system

33. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 33 What is Software Configuration Management? Definition: A set of management disciplines within the software engineering process to develop a baseline.A set of management disciplines within the software engineering process to develop a baseline.Description: Software Configuration Management encompasses the disciplines and techniques of initiating, evaluating and controlling change to software products during and after the software engineering process.Software Configuration Management encompasses the disciplines and techniques of initiating, evaluating and controlling change to software products during and after the software engineering process. Standards (approved by ANSI): IEEE 828: Software Configuration Management PlansIEEE 828: Software Configuration Management Plans IEEE 1042: Guide to Software Configuration ManagementIEEE 1042: Guide to Software Configuration Management

34. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 34 SCM Activities Configuration item identification is the modeling of the system as a set of evolving componentsis the modeling of the system as a set of evolving components Promotion management is the creation of versions for other developersis the creation of versions for other developers Release management is the creation of versions for the clients and usersis the creation of versions for the clients and users Branch management is the management of concurrent developmentis the management of concurrent development Variant management is the management of versions intended to coexistis the management of versions intended to coexist Change management is the handling, approval and tracking of change requestsis the handling, approval and tracking of change requests

35. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 35 SCM Roles Configuration Manager: Responsible for identifying configuration items. The configuration manager can also be responsible for defining the procedures for creating promotions and releasesResponsible for identifying configuration items. The configuration manager can also be responsible for defining the procedures for creating promotions and releases Change control board member: Responsible for approving or rejecting change requestsResponsible for approving or rejecting change requestsDeveloper: Creates promotions triggered by change requests or the normal activities of development. The developer checks in changes and resolves conflictsCreates promotions triggered by change requests or the normal activities of development. The developer checks in changes and resolves conflictsAuditor: Responsible for the selection and evaluation of promotions for release and for ensuring the consistency and completeness of this releaseResponsible for the selection and evaluation of promotions for release and for ensuring the consistency and completeness of this release

36. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 36 Terminology and Methodology What are Configuration Items,Configuration Items, Baselines,Baselines, SCM Directories,SCM Directories, Versions, Revisions and Releases?Versions, Revisions and Releases? The usage of the terminology presented here is not strict but varies for different configuration management systems.

37. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 37 Terminology: Configuration Item “An aggregation of hardware, software, or both, that is designated for configuration management and treated as a single entity in the configuration management process.” Software configuration items are not only program code segments but all type of documents that are produced during development, e.g.: all types of code filesall types of code files drivers for testsdrivers for tests analysis or design documentsanalysis or design documents user or developer manualsuser or developer manuals system configurations (e.g. version of compiler used)system configurations (e.g. version of compiler used) In some systems, not only software but also hardware configuration items (CPUs, bus speed frequencies) exist!

38. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 38 Terminology: Baseline “A specification or product that has been formally reviewed and agreed to by responsible management, that thereafter serves as the basis for further development, and can be changed only through formal change control procedures.” Examples: Baseline A: The API of a program is completely defined; the bodies of the methods are empty.Baseline A: The API of a program is completely defined; the bodies of the methods are empty. Baseline B: All data access methods are implemented and tested; programming of the GUI can start.Baseline B: All data access methods are implemented and tested; programming of the GUI can start. Baseline C: GUI is implemented, test-phase can start.Baseline C: GUI is implemented, test-phase can start.

39. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 39 More on Baselines Many naming schemes for baselines exist (1.0, 6.01a,...). 3 digit scheme: Release (Customer) Version (Developer) Revision (Developer) 7.5.5

40. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 40 Baselines in SCM Official Release Baseline A (developmental) Baseline B (functional) Baseline C (beta test) All changes relative to baseline AAll changes relative to baseline BAll changes relative to baseline C

41. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 41 Foo’95Foo’98 Standard SCM Directories Programmer’s Directory (IEEE Std: “Dynamic Library”)(IEEE Std: “Dynamic Library”) Completely under control of one programmer.Completely under control of one programmer. Central source code archive Release Promotion Master Directory (IEEE Std: “Controlled Library”)(IEEE Std: “Controlled Library”) Central directory of all promotions.Central directory of all promotions. Software Repository (IEEE Std: “Static Library”)(IEEE Std: “Static Library”) Externally released baselines.Externally released baselines.

42. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 42 Change Management Change management is the handling of change requests. A change request leads to the creation of a new release.A change request leads to the creation of a new release. General change process: The change is requested (this can be done by anyone including users and developers).The change is requested (this can be done by anyone including users and developers). The change request is assessed against project goals.The change request is assessed against project goals. Following the assessment, the change is accepted or rejected.Following the assessment, the change is accepted or rejected. If it is accepted, the change is assigned to a developer and implemented.If it is accepted, the change is assigned to a developer and implemented. The implemented change is audited.The implemented change is audited.

43. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 43 Change Management The complexity of the change management process varies with the project: Small projects can perform change requests informally and fast. Small projects can perform change requests informally and fast. Complex projects require detailed change request forms and the official approval by one or more managers. Complex projects require detailed change request forms and the official approval by one or more managers.

44. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 44 Two types of controlling change: Promotion: The internal development state of a software is changed.Promotion: The internal development state of a software is changed. Release: A set of promotions is distributed outside the development organization.Release: A set of promotions is distributed outside the development organization. Controlling Changes User Promotion Promote Policy Programmer Release Policy Software Repository Master Directory

45. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 45 Approaches for controlling change to libraries (Change Policies): Informal (good for research type environments)Informal (good for research type environments) Formal approach (good for externally developed CIs and for releases)Formal approach (good for externally developed CIs and for releases) Change Policies

46. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 46 Change Policies Whenever a promotion or a release is performed, one or more policies apply.Whenever a promotion or a release is performed, one or more policies apply. The purpose of change policies is to guarantee that each version, revision or release (see next slide) conforms to commonly accepted criteria.The purpose of change policies is to guarantee that each version, revision or release (see next slide) conforms to commonly accepted criteria. Examples for change policies: “No developer is allowed to promote source code which cannot be compiled without errors and warnings.”“No developer is allowed to promote source code which cannot be compiled without errors and warnings.” “No baseline can be released without having been beta-tested by at least 500 external persons.”“No baseline can be released without having been beta-tested by at least 500 external persons.”

47. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 47 Version vs. Revision vs. Release Version: An initial release or re-release of a configuration item associated with a complete compilation or recompilation of the item. Different versions have different functionality.An initial release or re-release of a configuration item associated with a complete compilation or recompilation of the item. Different versions have different functionality. Revision: Change to a version that corrects only errors in the design/code, but does not affect the documented functionality.Change to a version that corrects only errors in the design/code, but does not affect the documented functionality. Release: The formal distribution of an approved version.The formal distribution of an approved version.

48. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 48 Tools for SCM Software configuration management is normally supported by tools with different functionality. Examples: RCS: very old but still in use; only version control systemRCS: very old but still in use; only version control system CVS: based on RCS, allows concurrent working without lockingCVS: based on RCS, allows concurrent working without locking Perforce: repository server; keeps track of developer’s activitiesPerforce: repository server; keeps track of developer’s activities ClearCase: multiple servers, process modeling, policy check mechanismsClearCase: multiple servers, process modeling, policy check mechanisms

49. April 17, 2014CS410 – Software Engineering Lecture #18: Rationale Management 49 SCMP following the IEEE 828-1990 standard Tasks for the Configuration Managers Define configuration items Define promote /release policies Define responsibilities Set up configuration management system