Advanced Object-Oriented Analysis Concepts

Transcription

1 Advanced Object-Oriented Analysis Concepts Prof. Dr. U. Aßmann Technische Universität Dresden Institut für Software- und Multimediatechnik Gruppe Softwaretechnologie Version , June 12, 2006 Softwaretechnologie II, Prof. Uwe Aßmann 1

2 Contents Different kinds of classes and their relationships (UML class profiles) Facet-based classifications (powertypes) The UML metamodel 2 Prof. U. Aßmann, Softwaretechnologie II 2

3 Obligatory Reading Ghezzi Chap 4.2, 4.6 Pfleeger 12.4 Software Reusability [ if you have it: Maciaczek 5.4] Prof. U. Aßmann, Softwaretechnologie II 3

4 Literature I. Mathiassen, A. Munk-Madsen, P. Axel Nielsen, J. Stage. Objektorienterad analys och design. Studentliteratur. Ken Lunn. Software Development with UML. Palgrave-Macmillan. UML 2.0 report. Object Management Group (OMG). I. Jacobsen, G. Booch, J. Rumbaugh. The Unified Software Development Process. Addison-Wesley. The united process from the 3 amigos. Guiding through the OOD, from OOA to OOP. L. A. Maciaszek. Requirements Analysis and System Design. Addison-Wesley. Prof. U. Aßmann, Softwaretechnologie II 4

5 Common Class Patterns Softwaretechnologie II, Prof. Uwe Aßmann 5

6 How To Use Class Classifications UML allows for annotations of classes with stereotypes Classes can be marked-up, i.e., annotated with more semantics If the engineers knows classifications of classes, he can convey much more semantic in his models Learn the classes, use them as stereotypes UML 2.0 superstructure, Appendix B contains a huge set of standard stereotypes User can define stereotypes and collect them in UML profiles Prof. U. Aßmann, Softwaretechnologie II 6

7 Types Of Classes (Bahrami Profile) Concept class A concept is a notion on that many people agree in a domain (an ontology is a collection of concepts) Frequently used in a domain model Events class Event that happens over time <<concept>> <<event>> Organization class Captures knowledge about an organization People class Captures knowledge about people (actors) Places class Captures knowledge about locations <<organization>> <<people>> <<place>> Prof. U. Aßmann, Softwaretechnologie II 7

8 Types of Classes (Rumbaugh Profile) Physical class (e.g., Boat) Business class (e.g., Bill) Logical class (e.g., Timetable) Application class (e.g., BillingTransaction) Computer class (e.g., Set) Behavioral class (e.g., Cancellation) <<physical>> <<business>> <<logical>> <<application>> <<computer>> <<behavior>> Prof. U. Aßmann, Softwaretechnologie II 8

9 BCE/BCED Profile Boundary classes: Represent an interface item that talks with the user May persist beyond a run Control class: Controls the execution of a process, workflow, or business rules Does not persist Entity class: Describes persistent knowledge. Caches a persistent object from a database Database class Adapter class for the database <<boundary>> <<entity>> <<database>> <<control>> Often, Entity and Database classes are unified BCED is linked with the 4-tier architecture Prof. U. Aßmann, Softwaretechnologie II 9

10 Facet Classifications and Powertype Classes Softwaretechnologie II, Prof. Uwe Aßmann 10

11 Facet Classifications and Powertype Classes Sometimes, the object universe of a class falls into several partitions, facets A facet is a dimension of a model Every facet has its separate model The facets are independent of each other Final classes in the model inherit from every dimension (every facet) The facets compose a type, the powertype The following model of Living Beings has 3 facets Domain (where does an animal live?) Age Group of Animal 11 Prof. U. Aßmann, Softwaretechnologie II 11

12 Powertype LivingBeing Prof. U. Aßmann, Softwaretechnologie II 12

13 Facets Factorize Facets factorize inheritance hierarchies Facet 1 Facet 2 Services Cost Parking Refuel Maintenance Cheap Middle Expensive Minimal Service Don't Know Configured Service Powertype Service Prof. U. Aßmann, Softwaretechnologie II 13

14 Facets Can Be Implemented by Delegation One central facet, others are delegatees The powertype becomes a type, with a delegatee Facet 1 Facet 2 Services Cost Parking Refuel Maintenance Cheap Middle Expensive Minimal Service Don't Know Configured Service Powertype Service Prof. U. Aßmann, Softwaretechnologie II 14

15 How Can I Recognize Facets in Modelling? A facet is a partition of the object universe of the powertype A model is not a facet model, if some class exists, whose heirs do not partition the class (non-partitioned inheritance) If an object can belong to several subclasses or derivatives of a class, this indicates a facet model TypeOfEater Powertype Partition 1 QualityOfEater SortOfEater Partition 2 Gourmet Gourmand Vegetarian AllEater Prof. U. Aßmann, Softwaretechnologie II 15

16 Facets are Important UML 2.0 has facets in form of powertypes. They denote a special form of class Facets simplify inheritance hierarchies, because they factorize Less height, less breadth There are many complex models; use facets whereever possible. Prof. U. Aßmann, Softwaretechnologie II 16

17 The UML Metamodel Softwaretechnologie II, Prof. Uwe Aßmann 17

18 Objects, Classes, Metaclasses Metadata describes data A class can be considered as an object of the metalevel because it describes an object on the base level A metaclass describes a class and is part of the metamodel <<Object>> Peter:Person <<Class>> Person Person:Class Eat() Drink() Work() Sleep() <<Metaclass>> Class Delegate() Inherit() Extend() Instantiatate() world model Metamodel 18 Prof. U. Aßmann, Softwaretechnologie II 18

19 Metamodel of UML Structure Diagram Interface GenericClass Classifier Feature AbstractClass Class Method Attribute The UML metamodel describes UML. It contains all concepts of UML as classes. Here, stereotypes are described as classes. Some stereotypes are predefined, e.g., Interface, AbstractClass, GenericClass, Class are standard classes in the meta model of UML The UML metamodel models all diagram sublanguages of UML In the 80s, grammars were used for language specification. Now, with UML This indicates that UML can be used to specify languages 19 Prof. U. Aßmann, Softwaretechnologie II 19

20 Why is This Important? User-defined stereotypes are considered as extensions of the UML meta model Every time you define a stereotype, you extend the metamodel of UML UML is an extensible language Language extensions are called profiles On the long run, many application domains will have their profiles for object-oriented modelling Embedded and real-time systems Medical systems... Your task as engineer in an application domain will be to create UML profiles and metamodel extensions Problem The UML metamodel is not modeled with facets. Different aspects are mixed: not so nice! Prof. U. Aßmann, Softwaretechnologie II 20

21 Different Types of Class Relationships Softwaretechnologie II, Prof. Uwe Aßmann 21

22 Different Types of Relations Between Classes is-a: indicates similarity has-same-structure: the same structure (structural equality) behaves-like always-behaves-like: conformance, substitutability behaves-sometimes-like: Sometimes, A behaves-like B restrictedly-behaves-like: (restriction inheritance, extravagance) in general, A behaves-like B, but not in special situations is-a is acyclic, sometimes tree-like behaves-like can be symmetric Prof. U. Aßmann, Softwaretechnologie II 22

23 part-of Relation part-of: indicates containment [Maciaszek] exclusively-owns: The part cannot be switched to another owner. owns: The part has only one owner. Alias-free part-of ownership has-a: simple part-of. The part can be part of many entities. Aliases. member-of: The part can be part of many entities. all brothers are equal. composed-of (in UML): the part has the same life span as the whole and cannot exist standalone The part-of relation in a system is acyclic Can be layered Ownership relationships are tree-like Prof. U. Aßmann, Softwaretechnologie II 23

24 Hierarchical System Decomposition with owns-a Car <<owns>> Body Work Engine Dynamo Wheels Lights <<owns>> Cylinder Spark Plug Injection Nozzle Piston Rear Lights Front Lights No sharing 24 Prof. U. Aßmann, Softwaretechnologie II 24

25 Owns-A in Classes A class has features, i.e., attributes and methods The part-of relationship between the class and the features is treelike In database schemas, this is called a functional relationship The class name is a key to the attributes Prof. U. Aßmann, Softwaretechnologie II 25

26 Layered System Decomposition with part-of Part-of forms dags, sharing destroys trees Society Family University SportClub Government ChessClub Professors Students Uwe Frank Mary Sara 26 Prof. U. Aßmann, Softwaretechnologie II 26

27 The End Softwaretechnologie II, Prof. Uwe Aßmann 27