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Two System Architectures: MVC and DCA

Two System Architectures: MVC and DCA. Spinoff from the BabyUML project for Readable Programs. Trygve Reenskaug Department of Informatics University of Oslo. trygver@ifi.uio.no http://www.ifi.uio.no/~trygver. an Activity Network Planning example. My Problem. Project resources. User

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Two System Architectures: MVC and DCA

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  1. Two System Architectures:MVC and DCA Spinoff from the BabyUML project for Readable Programs Trygve Reenskaug Department of Informatics University of Oslo trygver@ifi.uio.no http://www.ifi.uio.no/~trygver MVC & DCA - ROOTS 2006

  2. an Activity Network Planningexample MVC & DCA - ROOTS 2006

  3. My Problem Project resources User tools Project activities actA actC actB actB actD Class Class Class Undisciplined communication →Spaghetti Class + superclasses + methods →Noodles MVC & DCA - ROOTS 2006

  4. BabyUML Goal:Readable Programs The price of reliability is the pursuit of the utmost simplicity (C.A.R. Hoare, 1980 Turing Award lecture) MVC & DCA - ROOTS 2006

  5. The BabyComponent =an object encapsulating other objects resource «Component» resource «Component» tool «Component» tool «Component» network «Component» network «Component» MVC & DCA - ROOTS 2006

  6. Baby ComponentsUniverse of Discourse «component» babydemo demoData tool «Interface» DemoDataIntf resource «Interface» Observer «Interface» ResourceIntf network «Interface» NetworkIntf «Class» ActivityDescr MVC & DCA - ROOTS 2006

  7. The BabyDemo programdemodata + network + resource + tool +IDE MVC & DCA - ROOTS 2006

  8. Baby ComponentsDivide and Conquer: the tool demoData tool «Interface» DemoDataIntf resource «component» babydemo «Interface» Observer «Interface» ResourceIntf network «Interface» NetworkIntf «Class» ActivityDescr MVC & DCA - ROOTS 2006

  9. Model – View - Controllerbridge gapMental Model – Computer mental model computer model Model User MVC & DCA - ROOTS 2006

  10. Model – View - ControllerMultiple Views on same Model 1 View * * mental model computer model Model User Run Demo MVC & DCA - ROOTS 2006

  11. Model – View - ControllerTool = Controller + Views Controller * 1 * * View Tool mental model computer model Model User Run Demo MVC & DCA - ROOTS 2006

  12. Model View ControllerRoles and Responsibilities MVC & DCA - ROOTS 2006

  13. Example: babydemo.toolClass structure java.applet.Applet java.awt.Panel Java.awt.Component Controller ButtonsView DependencyView GanttView ResourceView java.awt.Button ActivityView MVC & DCA - ROOTS 2006

  14. Example: babydemo.tool visual hierarchy (associations) ActivityView Controller 1 1 1 1 1 ButtonsView DependencyView GanttView ResourceView 1 1 1 1 * * java.awt.Button MVC & DCA - ROOTS 2006

  15. Example: babydemo.toolMVC collaboration structure Tool controller, observed, observer model. observed view, observer: ButtonsView view, observer: DependencyView view, observer: GanttView view, observer: ResourceView button: java.awt.Button view, observer: ActivityView MVC & DCA - ROOTS 2006

  16. The Anatomy ofbabyDemo.tool controller : Controller view :DependencyView view :ActivityView heim.ifi.uio.no/~trygver/2006/roots-2006/babyExample4.html MVC & DCA - ROOTS 2006

  17. MVCSynchronized Selection controller observer* a view update() selectedObject present User pointAndClickMouse actionPerformed() selectionEvent() notifyObserver() MVC & DCA - ROOTS 2006

  18. MVCtool component +IDE MVC & DCA - ROOTS 2006

  19. Baby Components: the networkDivide and Conquer demoData tool «Interface» DemoDataIntf resource «component» babydemo «Interface» Observer «Interface» ResourceIntf network «Interface» NetworkIntf «Class» ActivityDescr MVC & DCA - ROOTS 2006

  20. The Simple Componentindisciplined internals actD actA actC actB receive message façademethod façademethod MVC & DCA - ROOTS 2006

  21. The Declarative ComponentMember Objects in micro database babyBase interface void newActivity(String actName , …) void addDependency(String predNam , String succNam) Set<ActivityIntf> allActivities() Activity activityNamed(String actNam) Set<ActivityIntf> predecessorsOf(String actName) Set<ActivityIntf> successorsOf(String actName) add Dependency() newActivity() actA actC actB actD actC actD actA actB actC actD add Dependency() newActivity() babyBase with Member Objects and Member structure MVC & DCA - ROOTS 2006

  22. DCAseparate the whole from the Details Component looks outward Outward-lookingmethods and fields Member Object Inward-lookingmethods and fields Member Objects look inward MVC & DCA - ROOTS 2006

  23. Three simple operations MVC & DCA - ROOTS 2006

  24. The DCA ComponentData + Communication + Algorithm receive message a DCA Component MaestroMethod MaestroMethod actA actB actC actD Communication Algorithm micro “database” with Member Objects and structure Data ? MVC & DCA - ROOTS 2006

  25. The DCA Componentinvisible babyBase babyBase interface void newActivity(String actName , …) void addDependency(String predNam , String succNam) Set<ActivityIntf> allActivities() privateActivity activityNamed(String actNam) private Set<ActivityIntf> predecessorsOf(String actName) private Set<ActivityIntf> successorsOf(String actName) actA actC actB actD actC actD maestro only actA actB actC actD babyBase only add Dependency() newActivity() babyBase with Member Objects and Member structure MVC & DCA - ROOTS 2006

  26. public ActivityDescr activityDescriptorFor (String actName) actA actC actB actD actC actD receive message public class ActivityDescr { public String name; public Integer earlyStart, earlyFinish, duration, rank; public Color color; public Set<String> predecessors, successors; another Maestro Method activityDescriptorFor(“actC”) Which activity? What are preds, succs?? public class ActivityImpl implements ActivityIntf { MemberBase babyBase; private String name; private Integer earlyStart, duration, rank = 0; private Color color = Color.gray; actA actB actC actD babyBase MVC & DCA - ROOTS 2006

  27. algorithmactivityDescriptorFor()needs both predecessors and successors DescrCollab * * predecessors activity successors roles MVC & DCA - ROOTS 2006

  28. public ActivityDescr activityDescriptorFor (String actName) actD actA actC actB actA actB actC actD actA actC DescrCollab Collaboration = Communication context actB actD * * predecessors activity successors actC actD Algorithm Data receive message MaestroMethod activityDescriptorFor(“actC”) actA actB actC actD micro “database” MVC & DCA - ROOTS 2006

  29. “9.3.3 CollaboratioA collaboration describes a structure of collaborating elements (roles), each performing a specialized function, which collectively accomplish some desired functionality… Thus, details, such as the identity or precise class of the actual participating instances are suppressed.” UML 2.1: Collaboration BabyUML Collaboration + “9.3.4 CollaborationUse A collaboration use represents the application of the pattern described by a collaboration to a specific situation involving specific classes or instances playingthe roles of the collaboration.” BabyUML Query MVC & DCA - ROOTS 2006

  30. define successors (String actNam) as select succ from dependencies where pred.name = actNam Bind roles to Member Objects with queries ActivityDescriptorCollab DescrCollab * * predecessors predecessors activity activity successors successors * * define query activity (String actNam) as select act from activities where act.name = actNam define predecessors (String actNam) as select pred from dependencies where succ.name = actNam MVC & DCA - ROOTS 2006

  31. Algorithm (maestro)ActivityImpl:: activityDescriptor() MVC & DCA - ROOTS 2006

  32. D C ADataCommunicationAlgorithm MVC & DCA - ROOTS 2006

  33. babydemo Universe of Discourseinterface NetworkIntf MVC & DCA - ROOTS 2006

  34. define query frontActivities as select act from activities where act.earlyStart.isNil and ( select succ from dependencies where pred = act and pred.earlyStart.notNil ) isEmpty maestro methodvoid frontload (Integer firstWeek); receive message actD acD actD actA actA actA actC actC actC actD actD actA actA actC actC actB actB actB * predecessors frontloader actB actB actA actC frontCollab actB actD actC actD actB actB actD actB actA actC actC another Maestro Method frontload ( ) frontload (1) actA actB actC actD babyBase MVC & DCA - ROOTS 2006

  35. protectedclass FrontCollab { ActivityIntf frontloader; Set<ActivityIntf> predecessors; FrontCollab() { // activity that is ready to do : not done and all predecessors done frontloader = null; predecessors = new HashSet<ActivityIntf> (0); for (ActivityIntf act : activities) { if (act.earlyStart() == null) { Set<ActivityIntf> preds = predecessorsOf(act.name()); boolean predsDone = true; for ( ActivityIntf pred : preds) { if (pred.earlyStart() == null) { predsDone = false; break; } } if (predsDone) { frontloader = act; predecessors = preds; break; } } } } } babyBase.FrontCollab MVC & DCA - ROOTS 2006

  36. The DCA ComponentData + Communication + Algorithm roleX roleY actA actB actC actD Data structure and objects contained in micro ”database” receive message a DCA Component • Façade Method • creates Collaboration by binding Roles to Member Objectsthrough dynamic Queries. • triggers Communication as message interactionbetween Roles FaçadeMethod FaçadeMethod actD actB actC Algorithmsimplemented as Methodsin Member Objects MVC & DCA - ROOTS 2006

  37. Reduce coupling by enforcing component encapsulation. MVC to separate domain information and presentation Model components hold domain information Tool gives user direct access to information Viewobjects let user see and edit Controller object coordinates views DCA to organize component internal Member Objects Data: Member objects administred by BabyBase that ensured data integrity Conceptual Schema; BabyBase defines universe of discourse. External schemas: BabyBase creates collaborations for the external operations (Internal schema is the Member Object classes). Communication: Maestro methods in Component object triggers Member Object behavior Algorithms: What’s left in the Member Objects. Summary and Conclusion“make it so simple that there are obviously no deficiencies” • Reduce coupling by enforcing component encapsulation. • MVC to separate domain information and presentation • Model components hold domain information • Tool gives user direct access to information • View objects let user see and edit • Controller object coordinates views • DCA to organize component internal Member Objects • Data: Member objects administred by BabyBase that ensured data integrity • Conceptual Schema; BabyBase defines universe of discourse. • External schemas: BabyBase creates collaborations for the external operations • (Internal schema is the Member Object classes). • Communication: Maestro methods in Component object triggers Member Object behavior • Algorithms: What’s left in the Member Objects. MVC & DCA - ROOTS 2006

  38. The End Claim: MVC and DCA make for self-documenting code More info athttp://heim.ifi.uio.no/~trygver MVC & DCA - ROOTS 2006

  39. http://www.ifi.uio.no/~trygvermailto: trygver ‘at’ ifi.uio.no Trygve Reenskaug: The BabyUML discipline of programming (where A Program = Data + Communication + Algorithms). SoSym 5,1 (April 2006). DOI: 10.1007/s10270-006-0008-x. Trygve Reenskaug: The BabyUML Discipline of Programming. ECMDA 2005 keynote. http://heim.ifi.uio.no/~trygver/2005/babyuml/ECMDA2005-keynote.ppt Edsger Dijkstra: A Discipline of Programming, 1976 Charles Antony Richard Hoare: The Emperor's Old Clothes. 1980 Turing Award lecture. Comm.ACM 24, 2 (Feb. 1981) [UML] Unified Modeling Language: Superstructure. Version 2.1. Object Management Group (OMG) document ptc/06-04-02. http://www.omg.org Trygve Reenskaug: Empowering People with BabyUML: A sixth GenerationProgramming Language. Opening talk, ECOOP 2004, Oslo.http://heim.ifi.uio.no/~trygver/2004/ECOOP-04/EcoopHandout.pdf Trygve Reenskaug: Original MVC notes from Xerox PARC:http://heim.ifi.uio.no/~trygver/1979/mvc-1/1979-05-MVC.pdfhttp://heim.ifi.uio.no/~trygver/1979/mvc-2/1979-12-MVC.pdf Cattell, Barry: The Object Data Standard: ODMG 3.0. Academic Press,London, 2000. ISBN 1-55860-647-4 Erik Arisholm and Dag Sjøberg, A Controlled Experiment with Professionals to Evaluate the Effect of a Delegated versus Centralized Control Style on the Maintainability of Object-Oriented Software, Simula Research Laboratory Technical Report 2003-6http://www.simula.no/publication_one.php?publication_id=601 More reading …. MVC & DCA - ROOTS 2006

  40. ZZZThebabydemo ComponentUniverse of Discourse «component» babydemo tool demoData resource «Interface» DemoDataIntf «Interface» ResourceIntf network «Interface» NetworkIntf «Class»ActivityDescr MVC & DCA - ROOTS 2006

  41. Divide and ConquerthenetworkComponent «Class» DemoData DemoDataIntf «Class» resource ResourceIntf «MVC-component» tool «Class»ActivityDescr «DCA-component» network Applet NetworkIntf «component» babydemo MVC & DCA - ROOTS 2006

  42. babydemo.NetworkIntf +IDE MVC & DCA - ROOTS 2006

  43. public void newActivity(String actName , Integer duration, Color color); actA actB actC actD receive message newActivity() MaestroMethod babyBase with Member Objects and structure MVC & DCA - ROOTS 2006

  44. public void addDependency(String fromName , String toName); actA actC actB actD actC actD receive message MaestroMethod add Dependency actA actB actC actD babyBase MVC & DCA - ROOTS 2006

  45. babydemo.NetworkIntf MVC & DCA - ROOTS 2006

  46. maestro methodpublic List<String> activityNames() MVC & DCA - ROOTS 2006

  47. babydemo.NetworkIntf MVC & DCA - ROOTS 2006

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