Composite Structures

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1 Composite Structures Marie-Agnès Peraldi-Frati UNSA/I3S/INRIA UML 2 Composition Model Purpose: improve the black diamond composition Supports connections between parts at the same level of decomposition, in addition to the usual part-whole associations. Complex networks of entities can be represented within a single class, inherited to subclasses, with links maintained between objects playing parts at runtime. StructuredClassifiers See: UML 2.0 Superstructure C. Bock, UML 2 Composition model, JOT, vol 3, n 10, 2004, pp Sophia Antipolis

2 UML 1.x Composition UML 1.x composition is familiar to users as the black diamond notation on associations (called composite aggregation, or informally strong composition ). The black diamonds mean the same instance of ENGINE cannot be used simultaneously in an instance of CAR and an instance of BOAT, even though the class ENGINE is shared between the classes CAR and BOAT. The black diamond also means that an instance of ENGINE is destroyed when its containing instance of CAR or BOAT is destroyed. Note: Classes in the physical examples only describe information records of real or imagined physical objects. 3 -Sophia Antipolis Associations at the same level of decomposition While the UML 1.x model is fine for hierarchical decomposition, as in the figure in the previous slide, it has significant limitations when connecting elements at the same level of decomposition. The associations in the figure below are defined globally for all engines and boats, not in the context of individual cars and boats. This leads to erroneous interpretations. 4 -Sophia Antipolis

3 An incorrect instance model The right two wheels of YOURCAR receive power instead of the front two. The E1 instance of ENGINE is contained by MYCAR, but powers wheels contained by YOURCAR. The engine E2 is powering the correct propeller P1, but also powers wheels RIGHTFRONT1 and RIGHTBACK1. 5 -Sophia Antipolis Using generalized classes The REDEFINES property on association ends indicates that the association is restricted to the class at that end, and renamed for that purpose. Generalized class Generalized association This diagram is borrowed from C. Bock s paper. But it is not fully correct. See a better solution later. 6 -Sophia Antipolis

4 And yet, still misinterpretations However, even the above cumbersome class model do not prevent an engine in one car from powering wheels in another. This requires each individual car to have classes for its particular wheels and engine, so the association can be further specialized in each car. This is obviously impractical. 7 -Sophia Antipolis UML 2 Composition (1) New diagram specifically for composite structure Part How it is used (optional) Association being used Car Class=context e: Engine 1 : powers front: Wheel 2 Usage of other classes Name of the usage Usage of association back: Wheel 2 Nb of instances that will be used connector How it is used Class being used Boat e: Engine 1 : powers P: Propellor Sophia Antipolis

5 Connector Connectors represent communication links between instances of classes participating in an internal structure. They can be runtime instances of associations, or they can represent dynamic communication set up at runtime. Note that while associations between classes represent a link between any instances of those classes, a connector represents a link between only the two instances specified at each end of the connector (Definition vs. Usage) 9 Charles André - UNSA Connector end types UML specifies several rules for determinating the types of the elements at each end of a connector: If a connector represents an instance of an association, the types of the instances at either end of the connector must be the same types at either end of the association. If an instance at one end of a connector has required interfaces, the instance at the other end of the connector must provide one of those interfaces. If an instance at one end of a connector has required interfaces and a port is connected to the other end of the connector, the port must provide a required interface. 10 Charles André - UNSA

6 Ports (1) A port is a way to offer functionality from a composite structure without exposing the internal details of how the functionality is realized. Ports are associated with required/provided interfaces. Required interfaces show what the owning classifier may ask of its environment through a given port. Provided interfaces show what functionality a classifier exposes top the environment. Provided interface (type of the port) Required interface p is a port on the Engine class 11 Charles André - UNSA Ports (2) Behavioral port: the classifier owning the port provides the implementation of the functionality. Service port: the functionality is realized by internal elements. 12 Charles André - UNSA

7 Simple Example of Ports B.P. Douglass UML 2.0: Incremental Improvements for Scalability and Architecture, I-Logix Sophia Antipolis More elaborate example of Ports and Interfaces 14 -Sophia Antipolis

8 UML 2 Composition (2) An alternate representation: The SUBSETS property on association ends is another association specialization capability in UML 2. It indicates the association is specialized and renamed at that end, but does not restrict the inherited association to the class at that end (compare to REDEFINES). There is still a problem with redefines 15 -Sophia Antipolis Redefines/Subsets revisited (1) Generalization BoatEngine source powers transmitter 1 1..* Propeller CarEngine source powers transmitter 1 2 FrontWheel Two analogous concepts. Try to factorize! 16 -Sophia Antipolis

9 Redefines/Subsets revisited (2) PowerSource 1 source powers 1..* transmitter PowerTransmitter BoatEngine source powers transmitter 1 1..* Propeller CarEngine source powers transmitter 1 2 FrontWheel Possible instantiation Incorrect 17 -Sophia Antipolis Redefines/Subsets revisited (3) Break the relation 18 -Sophia Antipolis

10 Redefines/Subsets revisited (4) Derived union PowerSource 1 /source {union} /powers 1..* /transmitter {union} PowerTransmitter BoatEngine bsource {subsets source} powers btransmitter {subsets transmitter} 1 1..* Propeller CarEngine csource {subsets source} powers ctransmitter {subsets transmitter} 1 2 FrontWheel 19 -Sophia Antipolis Redefines/Subsets revisited (5) /invehicle {union} 1 Vehicle /invehicle {union} 1 /powersource {union} 1 1..* /powertransmitter {union} PowerSource 1 /source {union} 1..* /transmitter {union} PowerTransmitter Engine Propeller Wheel btransmitter {subsets transmitter} 1..* CarEngine 1 csource {subsets source} BoatEngine powers powers 1 bsource {subsets source} 2 ctransmitter {subsets transmitter} FrontWheel BackWheel 20 -Sophia Antipolis

11 UML 2 Composition (3) Instance model: 21 -Sophia Antipolis UML 2 Composition (4) An alternate representation of an instance model: Class being reused Instance name Association end name 22 -Sophia Antipolis

12 UML 2 Composition (5) Connectors can have multiplicities different from the association ends (parts) they relate. For example, a more general model of cars that covers both front-wheel drive and rear-wheel drive is shown in the Figure below. It uses a new association end w that navigates to all the wheels in a car. The new end has a multiplicity of 4, but the POWERS connector to it has a multiplicity of 2 on that end. This means for each car, two of the four wheels in the car will be powered. 23 -Sophia Antipolis UML 2 Composition (6) Application Window Button 2 Application does not own the Window 24 Charles André - UNSA

13 Inheritance of composite structure Connectors and association ends, including parts, inherit from class to subclass as all features do. Subclasses can specialize inherited parts and connectors, and introduce new ones. 25 -Sophia Antipolis Collaborations (1) One of the primary purpose for composite structures is to document how a particular piece of functionality is implemented within a system. This organization of elements to realize behavior is called a Collaboration. A Collaboration = collection of instances wired together using connectors to show the communication flow. Within a Collaboration, it is helpful to name the instances involved. Typically named based on its role in the collaboration. Representation: a dashed ellipsis with the name of the collaboration written inside. 26 Charles André - UNSA

14 Collaborations (2) Details of a collaboration: Collaboration Uses A collaboration use represents one particular use of a collaboration to explain the relationships between the properties of a classifier. A collaboration use shows how the pattern described by a collaboration is applied in a given context, by binding specific entities from that context to the roles of the collaboration. 27 Charles André - UNSA Component [UML-Glossary] Component = A modular part of a system that encapsulates its contents and whose manifestation is replaceable within its environment. A component defines its behavior in terms of provided and required interfaces. As such, a component serves as a type, whose conformance is defined by these provided and required interfaces (encompassing both their static as well as dynamic semantics). A Component is a kind of Classifier; it can have methods that realize interfaces, have statecharts and use cases. Components are coarse-grained elements that are usually replaced as a whole in the application. Component-based Development approaches use the metaphor of construction through assembly rather than construction via invention. 28 -Sophia Antipolis

15 Subsystems [UML-Glossary] Subsystem = A unit of hierarchical decomposition for large systems. A subsystem is commonly instantiated indirectly. Definitions of subsystems vary widely among domains and methods, and it is expected that domain and method profiles will specialize this construct. A subsystem may be defined to have specification and realization elements. A subsystem is a stereotype of both Package and Classifier. A subsystem is instantiable. A subsystem is used to organize the run-time system consisting of instances. The real work of a subsystem is implemented by the run-time instances contains within the subsystem. It offers up the collaborative behavior of the contained elements. Subsystems have three aspects: operation, specification, and implementation. The operations are the set of services directly offered by the Subsystem. 29 -Sophia Antipolis OCL Object Constraint Language

UML Constraint OCL is a formal language that provides a way to specify UML constraints 31 Charles André University of Nice OCL Part of the UML standard

16 UML Constraint OCL is a formal language that provides a way to specify UML constraints 31 Charles André University of Nice OCL Part of the UML standard Formalspecification language Object-oriented language Query-only language Why? because UML is not enough Where? 32

17 UML is not enough How many persons can own a car? How old must a car owner be? How can we require that a person must at most own one black car? Sources: Andreas Roth Introduction to OCL Praktikum WS0304: Formale Entwicklung objektorientierter Software 33 OCL Basic Types Built-in types that can be used in expressions: Boolean: true/false. Supports logical operators (and, or, xor, not, implies, if-then-else). Integer: 10, -56, etc. Supports the operators *, +, -, /, abs(). Real: 2.23, , etc. Supports the operators *, +, -, /, floor() String: "a string". Supports concat(), size(), substring(). Casting Casting objects from one type to another (related to generalization) oclastype() 34

18 Example 1 A vehicle owner must be at least 18 years old : 35 Class Invariants (1) A vehicle owner must be at least 18 years old : context Vehicle inv: self.owner.age >= 18 36

19 Class Invariants (1) A vehicle owner must be at least 18 years old : context Vehicle inv: self.owner.age >= Class Invariants (1) A vehicle owner must be at least 18 years old : context Vehicle inv: self.owner.age >= 18 38

20 Class Invariants (1) A vehicle owner must be at least 18 years old : context Vehicle inv: self.owner.age >= Class Invariants (1) A vehicle owner must be at least 18 years old : context Vehicle inv: self.owner.age >= 18 What does this mean, instead? inv: self.age >= 18 40

21 Class Invariants (1) A vehicle owner must be at least 18 years old : context Vehicle inv: self.owner.age >= 18 A car owner must be at least 18 years old : context Car inv: self.owner.age >= Class Invariants (2) Nobody has more than 3 vehicles : inv: self.fleet->size() <= 3 42

22 Class Invariants (2) All vehicles of a person are black : inv: self.fleet->forall(v v.color=color::black) 43 Class Invariants (2) All vehicles of a person are black : inv: self.fleet->forall(v v.color=color::black) 44 All cars of a person are black : inv: self.fleet->forall(v v.oclistypeof(car) implies v.color=color::black)

23 Collections (1) Collection = Set Set{1,6,2} * OrderedSet OrderedSet{1,6,2} *{ordered} Bag Bag{1,6,6,2} *{nonunique} Sequence Sequence{1,6,6,2} *{ordered,nonunique} OCL 2.0 supports collections of collections. Explicit flattening if needed 45 select(), reject(): Collections (1) specify a subset of the collection collect(): Specified a derived collection, which contains objects of a different type iterate(): Builds one value by iterating over a collection forall o c: P( o) 46 c->forall( o P(o) )

24 Class Invariants (3) Nobody has more than 3 black vehicules : inv: self.fleet->select(v v.color=color::black) ->size() <=3 47 Class Invariants (3) Nobody has more than 3 black vehicules : inv: self.fleet->select(v v.color=color::black) ->size() <=3 What does it mean? inv: self.fleet->iterate(v; acc: Integer=0 if v.color=color::black then acc+1 else acc endif ) <= 3 48

25 Class Invariants (3) Nobody has more than 3 black vehicules : inv: self.fleet->select(v v.color=color::black) ->size() <=3 What does it mean? inv: self.fleet->iterate(v; acc: Integer=0 if v.color=color::black then acc+1 else acc endif ) <= 3 A person younger than 18 owns no cars : inv: age < 18 implies self.fleet->forall(v not v.ocliskindof(car)) 49 Class Invariants (3) Nobody has more than 3 black vehicules : inv: self.fleet->select(v v.color=color::black) ->size() <=3 What does it mean? inv: self.fleet->iterate(v; acc: Integer=0 if v.color=color::black then acc+1 else acc endif ) <= 3 A person younger than 18 owns no cars : inv: age < 18 implies self.fleet->forall(v not v.ocliskindof(car)) 50 There is a red car : context Car inv: Car.AllInstances()->exists(c c.color=color::red)

26 Pre-/Postconditions (1) If setage(... ) is called with a not negative argument then the argument becomes the new value of the attribute age. ::setage(newage:integer) pre: newage >= 0 post: self.age = newage 51 Pre-/Postconditions (2) Calling birthday() increments the age of a person by 1. ::birthday( ) post: self.age = self.age@pre

27 Pre-/Postconditions (2) Calling birthday() increments the age of a person by 1. ::birthday( ) post: self.age = self.age@pre + 1 Calling getname() delivers the value of the attribute name. ::getname( ): String body: self.name -- or post: result = self.name 53 Query Calling getname() delivers the value of the attribute name. body: self.getname( ) = name 54

28 OCL Basics OCL is used to specify invariants of objects and pre- and post conditions of operations. Makes UML (class) diagrams more precise. OCL expressions use vocabulary of UML class diagram. OCL attribute accesses navigate through UML class diagram. context specifies about which elements we are talking. self indicates the current object. result the return value. 55 OCL Basics (cont d) OCL can talk about collections (here: sets). Operations on collections: > Example operations: select, forall, iterate iterate can simulate all other operations on collections. Queries (= side effect free operations) can be used in OCL expressions. 56

Metamodeling. Janos Sztipanovits ISIS, Vanderbilt University

Metamodeling. Janos Sztipanovits ISIS, Vanderbilt University Metamodeling Janos ISIS, Vanderbilt University janos.sztipanovits@vanderbilt.edusztipanovits@vanderbilt edu Content Overview of Metamodeling Abstract Syntax Metamodeling Concepts Metamodeling languages