1、Chapter 2, Modeling with UML,Overview: modeling with UML,What is modeling? What is UML? Use case diagrams Class diagramsNext lecture Sequence diagrams Activity diagrams,What is modeling?,Modeling consists of building an abstraction of reality. Abstractions are simplifications because: They ignore ir
2、relevant details and They only represent the relevant details. What is relevant or irrelevant depends on the purpose of the model.,Example: street map,Why model software?,Why model software?Software is getting increasingly more complex Windows XP 40 mio lines of code A single programmer cannot manag
3、e this amount of code in its entirety. Code is not easily understandable by developers who did not write it We need simpler representations for complex systems Modeling is a mean for dealing with complexity,Systems, Models and Views,A model is an abstraction describing a subset of a system A view de
4、picts selected aspects of a model A notation is a set of graphical or textual rules for depicting views Views and models of a single system may overlap each otherExamples: System: Aircraft Models: Flight simulator, scale model Views: All blueprints, electrical wiring, fuel system,Systems, Models and
5、 Views,Aircraft,Flightsimulator,Scale Model,Blueprints,Electrical Wiring,Models, Views and Systems (UML),System,Model,View,*,*,Depicted by,Described by,Airplane: System,Blueprints: View,Fuel System: View,Electrical Wiring: View,Scale Model: Model,Flight Simulator: Model,Concepts and Phenomena,Phenom
6、enon An object in the world of a domain as you perceive it Example: The lecture you are attending Example: My black watch Concept Describes the properties of phenomena that are common. Example: Lectures on software engineering Example: Black watches Concept is a 3-tuple: Name (To distinguish it from
7、 other concepts) Purpose (Properties that determine if a phenomenon is a member of a concept) Members (The set of phenomena which are part of the concept),Abstraction Classification of phenomena into concepts Modeling Development of abstractions to answer specific questions about a set of phenomena
8、while ignoring irrelevant details.,Concepts and phenomena,Concepts in software: Type and Instance,Type:An abstraction in the context of programming languages Name: int, Purpose: integral number, Members: 0, -1, 1, 2, -2, . . . Instance: Member of a specific type The type of a variable represents all
9、 possible instances the variable can takeThe following relationships are similar: “type” “instance” “concept” “phenomenon”,Abstract Data Types & Classes,Abstract data type Special type whose implementation is hidden from the rest of the system. Class: An abstraction in the context of object-oriented
10、 languages Like an abstract data type, a class encapsulates both state (variables) and behavior (methods) Class Vector Unlike abstract data types, classes can be defined in terms of other classes using inheritance,Application and Solution Domain,Application Domain (Requirements Analysis): The enviro
11、nment in which the system is operatingSolution Domain (System Design, Object Design): The available technologies to build the system,Object-oriented modeling,Application Domain,Solution Domain,Application Domain Model,System Model,Aircraft,TrafficController,FlightPlan,Airport,MapDisplay,FlightPlanDa
12、tabase,SummaryDisplay,TrafficControl,TrafficControl,UML Package,What is UML?,UML (Unified Modeling Language) An emerging standard for modeling object-oriented software. Resulted from the convergence of notations from three leading object-oriented methods: OMT (James Rumbaugh) OOSE (Ivar Jacobson) Bo
13、och (Grady Booch) Reference: “The Unified Modeling Language User Guide”, Addison Wesley, 1999. Supported by several CASE tools Rational ROSE TogetherJ,UML: First Pass,You can model 80% of most problems by using about 20 % UML We teach you those 20%,UML First Pass,Use case Diagrams Describe the funct
14、ional behavior of the system as seen by the user. Class diagrams Describe the static structure of the system: Objects, Attributes, Associations Sequence diagrams Describe the dynamic behavior between actors and the system and between objects of the system Statechart diagrams Describe the dynamic beh
15、avior of an individual object (essentially a finite state automaton) Activity Diagrams Model the dynamic behavior of a system, in particular the workflow (essentially a flowchart),UML first pass: Use case diagrams,Actor,Use case,Package,Use case diagrams represent the functionality of the system fro
16、m users point of view,UML first pass: Class diagrams,1,2,push() release(),Watch,Class,Association,Multiplicity,Attribute,Operations,Class diagrams represent the structure of the system,state,PushButton,UML first pass: Sequence diagram,Object,Message,Activation,Sequence diagrams represent the behavio
17、r as interactions,Actor,Lifeline,UML first pass: Statechart diagrams for objects with interesting dynamic behavior,State,Initial state,Final state,Transition,Event,Represent behavior as states and transitions,Other UML Notations,UML provide other notations that we will be introduced in subsequent le
18、ctures, as needed.Implementation diagrams Component diagrams Deployment diagrams Introduced in lecture on System Design Object constraint language Introduced in lecture on Object Design,UML Core Conventions,Rectangles are classes or instances Ovals are functions or use cases Instances are denoted wi
19、th an underlined names myWatch:SimpleWatch Joe:Firefighter Types are denoted with non underlined names SimpleWatch Firefighter Diagrams are graphs Nodes are entities Arcs are relationships between entities,Use Case Diagrams,Used during requirements elicitation to represent external behaviorActors re
20、present roles, that is, a type of user of the system Use cases represent a sequence of interaction for a type of functionality The use case model is the set of all use cases. It is a complete description of the functionality of the system and its environment,Actors,An actor models an external entity
21、 which communicates with the system: User External system Physical environment An actor has a unique name and an optional description. Examples: Passenger: A person in the train GPS satellite: Provides the system with GPS coordinates,Use Case,A use case represents a class of functionality provided b
22、y the system as an event flow.A use case consists of: Unique name Participating actors Entry conditions Flow of events Exit conditions Special requirements,Use Case Diagram: Example,Name: Purchase ticketParticipating actor: PassengerEntry condition: Passenger standing in front of ticket distributor.
23、 Passenger has sufficient money to purchase ticket.Exit condition: Passenger has ticket.,Event flow: 1. Passenger selects the number of zones to be traveled. 2. Distributor displays the amount due. 3. Passenger inserts money, of at least the amount due. 4. Distributor returns change. 5. Distributor
24、issues ticket.,Anything missing?,Exceptional cases!,The Relationship, relationships represent exceptional or seldom invoked cases. The exceptional event flows are factored out of the main event flow for clarity. Use cases representing exceptional flows can extend more than one use case. The directio
25、n of a relationship is to the extended use case,The Relationship, relationship represents behavior that is factored out of the use case. behavior is factored out for reuse, not because it is an exception. The direction of a relationship is to the using use case (unlike relationships).,Use Case Diagr
26、ams: Summary,Use case diagrams represent external behavior Use case diagrams are useful as an index into the use cases Use case descriptions provide meat of model, not the use case diagrams. All use cases need to be described for the model to be useful.,Class Diagrams,Class diagrams represent the st
27、ructure of the system. Used during requirements analysis to model problem domain concepts during system design to model subsystems and interfaces during object design to model classes.,Enumeration getZones() Price getPrice(Zone),*,*,Classes,A class represent a concept A class encapsulates state (att
28、ributes) and behavior (operations). Each attribute has a type. Each operation has a signature. The class name is the only mandatory information.,Name,Attributes,Operations,Signature,Instances,An instance represents a phenomenon. The name of an instance is underlined and can contain the class of the
29、instance. The attributes are represented with their values.,zone2price = 1, .20, 2, .40, 3, .60,Actor vs Instances,What is the difference between an actor , a class and an instance? Actor: An entity outside the system to be modeled, interacting with the system (“Passenger”) Class: An abstraction mod
30、eling an entity in the problem domain, must be modeled inside the system (“User”) Object: A specific instance of a class (“Joe, the passenger who is purchasing a ticket from the ticket distributor”).,Price Zone,Associations,Associations denote relationships between classes. The multiplicity of an as
31、sociation end denotes how many objects the source object can legitimately reference.,Enumeration getZones() Price getPrice(Zone),*,*,1-to-1 and 1-to-many Associations,Country,name:String,City,name:String,Has-capital,Polygon,draw(),Point,x: Integer,y: Integer,One-to-one association,One-to-many associ
32、ation,*,*,Many-to-Many Associations,StockExchange,Company,tickerSymbol,Lists,*,*,StockExchange,Company,Lists,1,*,tickerSymbol,SX_ID,From Problem Statement To Object Model,Pr,oblem Statement: A stock exchange lists many companies. Each company is uniquely identified by a ticker symbol,Class Diagram:,
33、StockExchange,Company,tickerSymbol,Lists,*,*,From Problem Statement to Code,public class StockExchange,private Vector m_Company = new Vector();,;,public class Company,public int m_tickerSymbol;,private Vector m_StockExchange = new Vector();,;,Pr,oblem Statement,:,A,stock exchange lists many companie
34、s.,Each company is identified by a ticker Symbol,Class Diagram:,Java Code,StockExchange,Company,tickerSymbol,Lists,*,*,Aggregation,An aggregation is a special case of association denoting a “consists of” hierarchy. The aggregate is the parent class, the components are the children class.A solid diam
35、ond denotes composition, a strong form of aggregation where components cannot exist without the aggregate. (Bill of Material),3,Exhaust system,Muffler,diameter,Tailpipe,diameter,1,02,Qualifiers,Qualifiers can be used to reduce the multiplicity of an association.,Inheritance,The children classes inhe
36、rit the attributes and operations of the parent class. Inheritance simplifies the model by eliminating redundancy.,Object Modeling in Practice: Class Identification,Foo,Betrag,CustomerId,Deposit(),Withdraw(),GetBalance(),Class Identification: Name of Class, Attributes and Methods,Object Modeling in
37、Practice: Encourage Brainstorming,Naming is important! Is Foo the right name?,Object Modeling in Practice ctd,CustomerId,1) Find New Objects,CustomerId,2) Iterate on Names, Attributes and Methods,Object Modeling in Practice: A Banking System,1) Find New Objects,2) Iterate on Names, Attributes and Me
38、thods,3) Find Associations between Objects,Has,4) Label the assocations,5) Determine the multiplicity of the assocations,*,Practice Object Modeling: Iterate, Categorize!,CustomerId(),Has,*,*,Packages,A package is a UML mechanism for organizing elements into groups (usually not an application domain
39、concept) Packages are the basic grouping construct with which you may organize UML models to increase their readability.A complex system can be decomposed into subsystems, where each subsystem is modeled as a package,DispatcherInterface,Notification,IncidentManagement,UML sequence diagrams,Used duri
40、ng requirements analysis To refine use case descriptions to find additional objects (“participating objects”) Used during system design to refine subsystem interfaces Classes are represented by columns Messages are represented by arrows Activations are represented by narrow rectangles Lifelines are
41、represented by dashed lines,Nested messages,The source of an arrow indicates the activation which sent the message An activation is as long as all nested activations Horizontal dashed arrows indicate data flow Vertical dashed lines indicate lifelines,ZoneButton,Dataflow,to be continued.,Iteration &
42、condition,Iteration is denoted by a * preceding the message name Condition is denoted by boolean expression in before the message name,ChangeProcessor,Iteration,Condition,to be continued.,continued from previous slide.,*,Creation and destruction,Creation is denoted by a message arrow pointing to the
43、 object. Destruction is denoted by an X mark at the end of the destruction activation. In garbage collection environments, destruction can be used to denote the end of the useful life of an object.,ChangeProcessor,continued from previous slide.,Creation,Destruction,Sequence Diagram Summary,UML seque
44、nce diagram represent behavior in terms of interactions. Useful to find missing objects. Time consuming to build but worth the investment. Complement the class diagrams (which represent structure).,State Chart Diagrams,State,Initial state,Final state,Transition,Event,Represent behavior as states and
45、 transitions,Activity Diagrams,An activity diagram shows flow control within a system An activity diagram is a special case of a state chart diagram in which states are activities (“functions”) Two types of states: Action state: Cannot be decomposed any further Happens “instantaneously” with respect
46、 to the level of abstraction used in the model Activity state: Can be decomposed further The activity is modeled by another activity diagram,Statechart Diagram vs. Activity Diagram,Active,Inactive,Closed,Archived,Incident- Handled,Incident- Documented,Incident- Archived,Statechart Diagram for Incide
47、nt (similar to Mealy Automaton) (State: Attribute or Collection of Attributes of object of type Incident),Activity Diagram for Incident (similar to Moore (State: Operation or Collection of Operations),Triggerless Transition,Completion of activity causes state transition,Event causes State transition
48、,Activity Diagram: Modeling Decisions,Activity Diagrams: Modeling Concurrency,Synchronization of multiple activities Splitting the flow of control into multiple threads,Synchronization,Splitting,Activity Diagrams: Swimlanes,Actions may be grouped into swimlanes to denote the object or subsystem that
49、 implements the actions.,Open,Incident,Allocate,Resources,Coordinate,Resources,Document,Incident,Archive,Incident,Dispatcher,FieldOfficer,What should be done first? Coding or Modeling?,It all depends.Forward Engineering: Creation of code from a model Greenfield projects Reverse Engineering: Creation of a model from code Interface or reengineering projects Roundtrip Engineering: Move constantly between forward and reverse engineering Useful when requirements, technology and schedule are changing frequently,
