Today s Agenda UML. CompSci 280 S Introduction to Software Development. 1.Introduction UML Diagrams. Topics: Reading:

Transcription

1 CompSci 280 S Introduction to Software Development Today s Agenda Topics: Introduction Activity Diagram Object interaction Sequence Diagram Reading: Booch G.,The Unified Modeling Language User Guide, ch 19. UML 2 UML Unified Modeling Language (UML) When creating complex OO systems, where do we start? When building complex systems, it might be worthwhile to plan things out before you start coding! When building a house, we usually have a set of plans. The UML is a standard notation for writing software blueprints UML is a language which allows us to graphically model an OO system in a standardised format. This helps us (and others!) understand the system. There are many different UML, allowing us to model designs from many different viewpoints. Roughly, there are Structure (documenting the architecture), e.g. class Behaviour (documenting the functionality), e.g. use-case 1.Introduction UML The UML is used to construct a model of a software system A model is a simplification of reality A model is thus an abstraction that exposes interesting properties while suppressing unnecessary detail A UML model comprises different, each focusing on a particular aspect of a system Class Model Interaction Use case Activity Component Component Deployment 3 4

2 1.Introduction UML diagram types Activity, which show the activities involved in a process or in data processing. Use case, which show the interactions between a system and its environment. Sequence, which show interactions between actors and perspective the system and between system components. Class, which show the object classes in the system and the associations between these classes., which show how the system reacts to internal and external events. Borrower Reserve book Borrow copy of book Return copy of book Update catalogue A Use Case diagram is user-centered and identifies system users (actors) and tasks. borrow( thecopy ) : LibraryMember thecopy : Copy oktoborrow An Interaction (sequence) diagram is concerned with dynamic behaviour and shows how objects exchange messages to fulfil a task. borrow borrowed browser Librarian : Book <<http>> Not borrowable A Class diagram shows the static structure of a system in terms of classes, interfaces and their relationships. returned( ) borrowed( ) [last copy] returned( ) Borrowable borrowed( ) [not last copy] A diagram shows the states and transitions for an instance of particular class (Book in this case). A Deployment diagram shows the deployment of software to hardware entities. servlet dbms 5 6 : PC Internet : Server LAN : Server 6 1.Introduction Tool Support: ArgoUML? You will draw some class and use-case. Options: ArgoUML Supports forward- and reverse-engineering. Class Java skeletons. Java classes class. Not on lab image you ll have to download and unzip the binary distribution in your echome directory (or on your USB pendrive) then double-click on argouml.jar (this is an executable jarfile ). Any general-purpose drawing package (e.g. Visio) By hand: This is your only option during exams and tests You ll have to scan your drawings into your assignments (which are submitted online) 2.Activity Diagram Activity describe the workflow behavior of a system. The describe the state of activities by showing the sequence of activities performed. they can show activities that are conditional or parallel. Activity do not give detail about how objects behave or how objects collaborate. An activity is an ongoing, though interruptible, execution of a step in a workflow (such as an operation or transaction) Represented with a rounded rectangle. Text in the activity box should represent an activity (verb phrase in present tense). 7 8

3 2. Activity Diagram How to Draw an Activity Diagram are read from top to bottom and have branches and forks to describe conditions and parallel activities. A fork is used when multiple activities are occurring at the same time. A branch describes what activities will take place based on a set of conditions. All branches at some point are followed by a merge to indicate the end of the conditional behavior started by that branch. After the merge all of the parallel activities must be combined by a join before transitioning into the final activity state. 2.Activity Diagram Activity Diagram Example Merge Branch Fork Start Join Activity End Object Interaction Object interaction show how class instances behave in terms of sending messages to one another This interactive behavior is represented in UML by two known as Sequence diagram and Collaboration diagram. The basic purpose of both the are similar. In UML, a sequence diagram is a popular form of interaction diagram where messages are time-ordered Interaction give a dynamic view of objects and show how they interact at run-time to fulfil a task Often used to model the way a use case is realized through a sequence of messages between objects. The purpose of Interaction is to: Model interactions between objects Assist in understanding how a system (a use case) actually works Verify that a use case description can be supported by the existing classes Identify responsibilities/operations and assign them to classes 3.Object Interaction Interaction diagram notation Key elements of interaction are objects and messages (method calls) Active Objects Life line appears below active objects to indicate their lifespan Messages Arrowed lines that indicated communication between objects Notations: An instance, named object, of an unspecified class An instance, named object, of a class named Class An unnamed instance of class Class Message m m Message reply r (optional) r Object lifeline Focus of control (optional) object object : Class : Class 11 12

4 4.Sequence Diagram Objects & Messages an Order Line 4.Sequence Diagram Example: Objects: An object in a sequence diagram is rendered as a box with a dashed line descending from it. The line is called the object lifeline, and it represents the existence of an object over a period of time. Messages Messages are rendered as horizontal arrows being passed from object to object as time advances down the object lifelines. Conditions ( such as ) indicate when a message gets passed Return: This arrow indicates a return from a previous message, not a new message. an Order Line check() remove() a Stock Item Time Increasing --> All lines should be horizontal to indicate instantaneous actions. Additionally if ActivityA happens before ActivityB, ActivityA must be above activity A Sequence Diagram Iterations Iteration: An iteration marker, such as * (as shown), or *[i = 1..n], indicates that a message will be repeated as indicated. an Order * prepare() Iteration marker a Order Line an Order Entry window Object prepare() Message an Order an Order Line a Stock Item * prepare() Iteration check() remove() Return Condition needstoreorder() [Fowler,97] Self-Delegation [needstoreorder = true ] new A Reorder Item new A Delivery Item Creation 15 16

5 5. Examples: Part of a Vending Machine Banking task: applying interest to a savings account driver : Customer : SavingsAccount balance : accounts( ) applyinterest( ) Points to note: Sequence are timeordered Actual arguments can include literals or references to participating objects multiply( 0.08 ) interest create( ) interest : add( interest ) newbalance create( ) newbalance : create( Transaction.INTEREST, interest, this ) : Transaction Sequence Diagram Exercise: ATM Machine Draw a sequence diagram on cash withdrawal from ATM 19