1 / 50

UML Distilled

UML Distilled. Design by contract. Object-Oriented Software Construction by Bertrand Meyer, Prentice Hall The presence of a precondition or postcondition in a routine is viewed as a contract. Rights and obligations. Parties in the contract: class and clients

vanceb
Download Presentation

UML Distilled

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. UML Distilled

  2. Design by contract • Object-Oriented Software Construction by Bertrand Meyer, Prentice Hall • The presence of a precondition or postcondition in a routine is viewed as a contract.

  3. Rights and obligations • Parties in the contract: class and clients • require pre, ensure post with method r: If you promise to call r with pre satisfied then I, in return, promise to deliver a final state in which post is satisfied. • Contract: entails benefits and obligations for both parties

  4. Rights and obligations • Precondition binds clients • Postcondition binds class

  5. Example

  6. If precondition is not satisfied • If client’s part of the contract is not fulfilled, class can do what it pleases: return any value, loop indefinitely, terminate in some wild way. • Advantage of convention: simplifies significantly the programming style.

  7. Source of complexity • Does data passed to a method satisfy requirement for correct processing? • Problem: no checking at all or: multiple checking. • Multiple checking: conceptual pollution: redundancy; complicates maintenance • Recommended approach: use preconditions

  8. Class invariants and class correctness • Preconditions and postconditions describe properties of individual methods • Need for global properties of instances which must be preserved by all routines • 0<=nb_elements; nb_elements<=max_size • empty=(nb_elements=0);

  9. Class invariants and class correctness • A class invariant is an assertion appearing in the invariant clause of the class. • Must be satisfied by all instances of the class at all “stable” times (instance in stable state): • on instance creation • before and after every remote call to a routine (may be violated during call)

  10. Class invariants and class correctness • A class invariant only applies to public methods; private methods are not required to maintain the invariant.

  11. Invariant Rule • An assertion I is a correct class invariant for a class C iff the following two conditions hold: • The constructor of C, when applied to arguments satisfying the constructor’s precondition in a state where the attributes have their default values, yields a state satisfying I. • Every public method of the class, when applied to arguments and a state satisfying both I and the method’s precondition, yields a state satisfying I.

  12. Invariant Rule • Precondition of a method may involve the initial state and the arguments • Postcondition of a method may only involve the final state, the initial state (through old) and in the case of a function, the returned value. • The class invariant may only involve the state

  13. Invariant Rule • The class invariant is implicitly added (anded) to both the precondition and postcondition of every exported routine • Could do, in principle, without class invariants. But they give valuable information. • Class invariant acts as control on evolution of class • A class invariant applies to all contracts between a method of the class and a client

  14. Resource Allocation reqs <JobCategory> <Facility> 0..* type provides 0..* <Job> when: TimeInterval schedule allocated <Resource> 0..* 0..1 inv Job::allocated<>0 ==> allocated.provides->includesAll(type.reqs) --Any allocated resource must have the required facilities inv Resource::jo1, jo2: Job:: (schedule->includesAll({jo1,jo2}) ==> jo1.when.noOverlap(jo2.when) -- no double-booking of resources

  15. Collaborations in UMLUML Distilled: page 113 • A collaboration is a name given to the interaction among two or more classes. • You can also add a class diagram to show the classes that participate in the collaboration.

  16. Collaborations • Use them to show common behavior. • Often you may find that the same collaboration is used by different classes in the system. • You can illustrate this by parameterizing the collaboration.

  17. Roles • Show roles that objects play in collaboration. • UML also uses the term pattern for a parameterized collaboration.

  18. Collaboration basics collaboration checkDef { roleCd_graph { out check(){}; // out: provided getClasses(){}; // local method in getAll = // in: expected from Cd_graph bypassing Neighbors to Vertex; } roleNeighbors { } roleVertex { } } A collaboration is self-contained and parameterized by roles and expected members.

  19. Java Code: What is the collaboration? Cd_graph{{ void isDefined(ClassGraph cg){ checkDefined(cg, getClasses(cg));} HashSet getClasses(ClassGraph cg){ Strategy getAll = new Strategy( "from Cd_graph bypassing Neighbors to Vertex"); TraversalGraph tg = new TraversalGraph(getAll, cg); Visitor v = new Visitor(){ HashSet return_val = new HashSet(); void before(Vertex v){ return_val.add(v.get_vertex_name());} public Object getReturnValue(){return return_val;}}; tg.traverse(this,v); return (HashSet)v.getReturnValue(); }

  20. Java Code: What is the collaboration? void checkDefined(ClassGraph cg, HashSet tempClassSet){ final HashSet classHash = tempClassSet; Strategy checkAll = new Strategy(” from Cd_graph through Neighbors to Vertex"); TraversalGraph tg = new TraversalGraph(checkAll, cg); tg.traverse(this, new Visitor(){ void before(Vertex v){ if(!classHash.contains(v.get_vertex_name())){ System.out.println("The class "+ v.get_vertex_name() + " is undefined."); }}});} }}

  21. Find undefined classes vertices getAll * Cd_graph * Vertex checkAll neighbors * * vertices Neighbors getAll = from Cd_graph bypassing Neighbors to Vertex checkAll = from Cd_graph through Neighbors to Vertex

  22. High-level description • It is useful to have a high-level description of the collaboration besides the Java source code. Useful documentation. • Ultimately we are interested in the executable form of the collaboration (Java source code).

  23. Collaboration 1: with strategies collaboration checkDef { participantCd_graph { out check(){(uses getClasses, checkDefined)}; getClasses(){(uses getAll)}; checkDefined(){(uses checkAll)}; in getAll = from Cd_graph bypassing Neighbors to Vertex; incheckAll = from Cd_graph through Neighbors to Vertex; } participantNeighbors { } participantVertex { } }

  24. Collaboration 2: with accessors collaboration checkDef { participantCd_graph { out check(){(uses getClasses, checkDefined)}; getClasses(){(uses getAll)}; checkDefined(){(uses checkAll)}; in getNeighbors(); in getVertices(); getAll(){return getVertices()}; // from Cd_graph bypassing Neighbors to Vertex; checkAll(){return getNeighbors().getVertices();} // from Cd_graph through Neighbors to Vertex; participantNeighbors { in getVertices(); } participantVertex { } }

  25. Use of 2. collaboration Need to provide the expected methods (in methods) and provide name map (identity in this case): Cd_graph: in getNeighbors(); Cd_graph: in getVertices(); Neighbors: in getVertices(); Cd_graph:getNeighbors(){ return cg.gather(this,”from Cd_graph to Neighbors”);} Cd_graph:getVertices(){ return cg.gather(this, ”from Cd_graph bypassing Neighbors to Vertex;”);} Neighbors:getVertices(){ return cg.gather(this,”from Neighbors to Vertex”);}

  26. Use of 1. collaboration Need to provide the expected methods (in methods) and provide name map (identity in this case): Cd_graph: in getAll // use default incheckAll // use default

  27. The Collaboration in Action • Computer Science • Project • Smaller class graph for class graphs • Mathematics

  28. Class dictionary (part 1) Cd_graph = <adjacencies> Nlist(Adjacency) EOF. Adjacency = < source > Vertex < ns > Neighbors "." . Neighbors : Neighbors_wc . Neighbors_wc :Construct_ns | Alternat_ns common < construct_ns > List(Any_vertex). Construct_ns = "=". Alternat_ns = ":" < alternat_ns > Bar_list(Term) [<common> Common]. Common = "common". Any_vertex : Opt_labeled_term | Optional_term | Syntax_vertex .

  29. Class dictionary (part 2) Vertex = < vertex_name > Ident. Syntax_vertex : Regular_syntax common. Regular_syntax = < string > String . Opt_labeled_term : Labeled | Regular common <vertex> Term. Regular = . Labeled = "<" < label_name > Ident ">" . Term : Normal common <vertex> Vertex. Normal = . Optional_term = "[" <opt> Sandwich(Opt_labeled_term) "]".

  30. getAll = from Cd_graph bypassing Neighbors to Vertex checkAll = from Cd_graph through Neighbors to Vertex Class dictionary (part 1) Cd_graph = <adjacencies> Nlist(Adjacency) EOF. Adjacency = < source > Vertex < ns > Neighbors "." . Neighbors : Neighbors_wc . Neighbors_wc :Construct_ns | Alternat_ns common < construct_ns > List(Any_vertex). Construct_ns = "=". Alternat_ns = ":" < alternat_ns > Bar_list(Term) [<common> Common]. Common = "common". Any_vertex : Opt_labeled_term | Optional_term | Syntax_vertex .

  31. getAll = from Cd_graph bypassing Neighbors to Vertex checkAll = from Cd_graph through Neighbors to Vertex Class dictionary (part 1) Cd_graph =<adjacencies> Nlist(Adjacency) EOF. Adjacency= < source > Vertex < ns > Neighbors "." . Neighbors : Neighbors_wc . Neighbors_wc :Construct_ns | Alternat_ns common < construct_ns > List(Any_vertex). Construct_ns = "=". Alternat_ns = ":" < alternat_ns > Bar_list(Term) [<common> Common]. Common = "common". Any_vertex : Opt_labeled_term | Optional_term | Syntax_vertex .

  32. getAll = from Cd_graph bypassing Neighbors to Vertex checkAll = from Cd_graph through Neighbors to Vertex Class dictionary (part 2) Vertex = < vertex_name > Ident. Syntax_vertex : Regular_syntax common. Regular_syntax = < string > String . Opt_labeled_term : Labeled | Regular common <vertex> Term. Regular = . Labeled = "<" < label_name > Ident ">" . Term : Normal common <vertex> Vertex. Normal = . Optional_term = "[" <opt> Sandwich(Opt_labeled_term) "]".

  33. getAll = from ClassG bypassing Body to ClassName UML class diagram ClassG 0..* Entry EParse entries ClassG BParse ClassDef Body parts Part className 0..* ClassName Concrete Abstract AOO / UML / OCL/Strategies

  34. checkAll = from ClassG through Body to ClassName UML class diagram ClassG 0..* Entry EParse entries ClassG BParse ClassDef Body parts Part className 0..* ClassName Concrete Abstract AOO / UML / OCL/Strategies

  35. change of domain: from Computer Science to Mathematics Example: x = 1.0 . y = (+ x 4.0). z = (* x y). Equation System EquationSystem = <equations> List(Equation). Equation = <lhs> Variable “=“ <rhs> Expression “.”. Variable = Ident. Expression : Simple | Compound. Simple : Variable | Numerical. Compound = “(“ Op <args> List(Expression) “)”. Op : Add | Mul. Add = “+”. Mul = “*”. Numerical = float. Write a program for: Are all variables in an equation system defined? (disregard order of equations)

  36. Make More Reusable Cd_graph{{ String vi = “from Vertex to edu.neu.ccs.demeter.Ident”; void isDefined(ClassGraph cg){ checkDefined(cg, getClasses(cg));} HashSet getClasses(ClassGraph cg){ Strategy getAll = new Strategy( "from Cd_graph bypassing Neighbors to Vertex"); TraversalGraph tg = new TraversalGraph(getAll, cg); Visitor v = new Visitor(){ HashSet return_val = new HashSet(); void before(Vertex v){ return_val.add(cg.fetch(v, vi) );} public Object getReturnValue(){return return_val;}}; tg.traverse(this,v); return (HashSet)v.getReturnValue(); }

  37. Make More Reusable void checkDefined(ClassGraph cg, HashSet tempClassSet){ final HashSet classHash = tempClassSet; Strategy checkAll = new Strategy(” from Cd_graph through Neighbors to Vertex"); TraversalGraph tg = new TraversalGraph(checkAll, cg); tg.traverse(this, new Visitor(){ void before(Vertex v){ Ident vn = cg.fetch(v, vi); if (!classHash.contains(vn)){ System.out.println("The object "+ vn + " is undefined."); }}});} }}

  38. Example: x = 1.0 . y = (+ x 4.0). z = (* x y). Equation System EquationSystem = <equations> List(Equation). Equation = <lhs> Variable “=“ <rhs> Expression “.”. Variable = Ident. Expression : Simple | Compound. Simple : Variable | Numerical. Compound = “(“ Op <args> List(Expression) “)”. Op : Add | Mul. Add = “+”. Mul = “*”. Numerical = float. Write a program for: Are all variables in an equation system defined? (disregard order of equations)

  39. Name map

  40. Adaptive Object-Oriented Design Find undefined things definedThings * System * Thing usedThings * * * UsedThingsHolder definedThings= from System bypassing UsedThingsHolder to Thing usedThings = from System through UsedThingsHolder to Thing

  41. usedThings = from EquationSystem through Expression to Variable Example: x = 1.0 . y = (+ x 4.0). z = (* x y). Equation System EquationSystem = <equations> List(Equation). Equation = <lhs> Variable “=“ <rhs> Expression “.”. Variable = Ident. Expression : Simple | Compound. Simple : Variable | Numerical. Compound = “(“ Op <args> List(Expression) “)”. Op : Add | Mul. Add = “+”. Mul = “*”. Numerical = float.

  42. definedThings= from EquationSystem bypassing Expression to Variable Example: x = 1.0 . y = (+ x 4.0). z = (* x y). Equation System EquationSystem = <equations> List(Equation). Equation =<lhs> Variable “=“ <rhs> Expression “.”. Variable = Ident. Expression : Simple | Compound. Simple : Variable | Numerical. Compound = “(“ Op <args> List(Expression) “)”. Op : Add | Mul. Add = “+”. Mul = “*”. Numerical = float.

  43. Name map

  44. Conclusion Collaborations • Collaborations are an important architectural element in object-oriented design. • Separate collaboration from its use.

  45. Collaboration CheckUnique:3 Roles //checks for unique parts. // Collaboration CheckUnique // role System // out void checkUnique(final ClassGraph cg) // in Strategy getAllUnitsToBeChecked // role UnitToBeChecked // in Strategy checkAllParts // role NotDuplicated // System = List(UnitToBeChecked). // UnitToBeChecked = List(NotDuplicated). // NotDuplicated = Ident.

  46. Collaboration CheckUniquewith role play //checks for unique parts. // Collaboration CheckUnique // role System played by Grammar // out void checkUnique(final ClassGraph cg) // in Strategy getAllUnitsToBeChecked // role UnitToBeChecked played by Statement // in Strategy checkAllParts // role NotDuplicated played by NonTerminal // System = List(UnitToBeChecked). // UnitToBeChecked = List(NotDuplicated). // NotDuplicated = Ident.

  47. Collaboration CheckUniquewith role play 2 //checks for unique parts. // Collaboration CheckUnique // role System played by Cd_graph // out void checkUnique(final ClassGraph cg) // in Strategy getAllUnitsToBeChecked // role UnitToBeChecked played by Adjacency // in Strategy checkAllParts // role NotDuplicated played by Vertex // System = List(UnitToBeChecked). // UnitToBeChecked = List(NotDuplicated). // NotDuplicated = Ident.

  48. Program part 1 System{ {{ Strategy getAllUnitsToBeChecked = … from System to UnitToBeChecked … void checkUnique(final ClassGraph cg){ cg.traverse(this, getAllUnitsToBeChecked, new Visitor(){ void before(UnitToBeChecked a){ a.checkDuplicateParts(cg);} });}}}}

  49. Program part 2 UnitToBeChecked{ {{ Strategy checkAllParts = … from UnitToBeChecked to NotDuplicated … void checkDuplicateParts(ClassGraph cg){ cg.traverse(this, checkAllParts, new Visitor(){ HashSet hParts = new HashSet(); void before(NotDuplicated l){ if(!hParts.add(l.get_ident())){ System.out.println("Element "+ l.get_ident() + " is not unique."); }}});}}}}

  50. Generic System UnitToBeChecked NotDuplicated Project Cd_graph Adjacency Vertex Map

More Related