Steps in Using COMET/UML

Transcription

1 SWE 621: Software Modeling and Architectural Design Lecture Notes on Software Design Lecture 5- Finite State Machines and Statecharts Hassan Gomaa Dept of Computer Science George Mason University it Fairfax, VA Copyright 2011 Hassan Gomaa All rights reserved. No part of this document may be reproduced in any form or by any means, without the prior written permission of the author. This electronic course material may not be distributed by or posted on any other World Wide Web site without the prior written permission of the author. Steps in Using COMET/UML 1 Develop Software Requirements Model 2 Develop Software Analysis Model Develop static model of problem domain (Chapter 7) Structure system into objects (Chapter 8) Develop statecharts for state dependent objects (Chapter 10) Develop object interaction diagrams for each use case (Chapter 9, 11) 3 Develop Software Design Model User 1 Requirements 2 Modeling Analysis Modeling 4 Throwaway Prototyping 3 5 Design Modeling 6 Incremental Software Construction 7 Incremental Software Integration 8 Customer Incremental Prototyping 9 15 System Testing

2 Finite State Machines and Statecharts 5. Section FSM Hassan Gomaa References: H. Gomaa, Chapter 10 - Software Modeling and Design, Cambridge University Press, February 2011 H. Gomaa, Chapter 10 - Designing Concurrent, Distributed, and Real-Time Applications with UML, Addison Wesley Object Technology Series, July, 2000 Copyright 2011 Hassan Gomaa All rights reserved. No part of this document may be reproduced in any form or by any means, without the prior written permission of the author. Finite State Machines and Statecharts Many information and real-time systems are state dependent Action depends not only on input event Also depends on state of system Finite State Machine Finite number of states Only in one state at a time Statechart Graphical representation of finite state machine States are rounded boxes Transitions are arcs Statechart relates events and states fsm-4 2

3 Figure 2.7 UML notation for statechart: composite state with sequential substates Composite state A Initial State Event Substate A1 Entry / Action Exit / Action Event [condition] / Action Substate A2 Event / Action Final State fsm-5 States and Events State A recognizable situation Exists over an interval of time Represents an interval between successive events Event A discrete signal that happens at a point in time Also known as a stimulus Has no duration Causes change of state Referred to as state transition fsm-6 3

4 Figure 10.1 Example of Events and States Card Inserted Waiting for PIN PIN Entered Validating PIN Valid PIN Waiting for Customer Choice 7 Events and Conditions State transition label Event [Condition] Condition is a Boolean function Conditions are optional on statecharts Condition is true for finite period of time When event occurs, condition must be true for state transition to occur. If condition is false, state transition does not occur fsm-8 4

5 Figure 10.6 Example of Events and Conditions 9 Actions State transition label Event / action(s) Event [condition] / action(s) Action Executed as a result of state transition Executes instantaneously at state transition Terminates itself Is optional fsm-10 5

6 Figure 10.8 Example of actions Card Inserted / Get PIN PIN entered / Validate PIN Waiting for PIN Invalid PIN / Invalid PIN Prompt Validating PIN Third Invalid, Stolen / Confiscate Valid PIN / Display menu Waiting for Customer Choice Confiscating fsm-11 Entry and Exit Actions Entry action Action executed on entry into state Entry / action E.g., Start Cooking Exit action Action executed on exit from state Exit / action E.g, Stop Cooking fsm-12 6

7 Figure Example of entry action Fig a: Actions on state transitions Fig b: Entry action 13 Figure Example of exit action Fig a Actions on state transitions Fig b: Exit action 14 7

8 Hierarchical Statecharts Disadvantages of State Transition Diagrams and Flat Statecharts Complex State Transition Diagrams get very cluttered Limited capability for managing complexity Hierarchical Statecharts Based on Harel Statecharts Notation for hierarchical decomposition of state transition diagrams Composite state decomposed into substates Default entry states Transition out of composite state corresponds to transition out of every substate 15 Figure 10.9 Example of same event and action on different state transitions 16 8

9 Figure Example of hierarchical statechart showing composite state and substates Card Inserted / Get PIN Entry / Display Welcome Customer Input Waiting for PIN Cancel / Eject Ejecting PIN Entered / Validate PIN Invalid PIN / Invalid PIN Prompt Third Invalid PIN, Card Stolen, Card Expired / Confiscate Validating PIN Confiscating Valid PIN / Display Menu Waiting for Customer Choice 17 Hierarchical Statecharts Sequential decomposition When object is in composite state It is in one and only one of substates Transition into composite state Must be to one and only one of substates Aggregation g of state transitions If same event causes transition out of every substate Then aggregate into transition out of composite state 18 9

10 Figure Example of hierarchical statechart showing composite state without substates 19 Guidelines on Statecharts State name must be passive not active Represents time period when something is happening, e.g., Waiting for PIN Identifiable situation, e.g.,, Initial State names must be unique Must be able to exit from every state Flat statechart Statechart is only in one state at a time Hierarchical statechart sequential decomposition Statechart is only in one substate at a time fsm-20 10

11 Guidelines on Statecharts Event is the cause of the state transition Event happens at a moment in time Event name indicates something has just happened e.g, Card Inserted, Door Closed Action is the result of the state transition Action is a command, e.g., Dispense Cash, Start Cooking Action executes instantaneously Activity executes throughout a given state More than one action possible with a state transition No sequential dependency between actions Condition is a Boolean value Event [Condition] State transition only occurs if Event happens & Condition is True Condition is True over some interval of time Actions, Activities and Conditions are optional fsm-21 Developing Statechart from Use Case Develop state dependent use case Start with scenario (one path through use case) Consider sequence of interactions between actor and system Consider sequence of external events Input event from external environment Causes state transition to new state Action may result from state transition Initially develop flat statechart fsm-22 11

12 Figure 19.1 Banking System use case model Withdraw Funds «include» Query Account «include» «include» Validate PIN ATM Customer Transfer Funds Add Cash Startup Shutdown Operator fsm-23 Figure Statechart for ATM Control - Validate PIN use case Card Inserted / Get PIN Entry/ Display Welcome Waiting for PIN PIN Entered / Validate PIN Validating PIN Waiting for Customer Choice Valid PIN / Display Menu, Udt Update Statust fsm-24 12

13 Figure Statechart for ATM Control - Withdraw Funds use case Entry / Display Welcome After (Elapsed Time) [Closedown Not Requested] Terminating Ejecting Card Ejected / Display Ejected Receipt Printed / Eject Waiting For Customer Choice Withdrawal Selected / Request Withdrawal, Printing Cash Dispensed / Print Receipt, Display Cash Dispensed Confirm Cash Dispensed Withdrawal Withdrawal Approved / Dispense Cash, Update Status Dispensing fsm-25 Developing Statechart from Use Case (continued) Consider alternative external events Could result in additional states Could result in additional state transitions Develop hierarchical statechart States that can be aggregated to form composite state Event causing transition from several states Create composite state t with one transition out of composite state Instead of many transitions out of substates fsm-26 13

14 Example of integrated statechart Waiting for PIN PIN entered Invalid PIN Card Inserted Cancel Cancel Card Confiscated Insufficient Cash After (Elapsed Time) Terminating Card Ejected Validating PIN Valid PIN Waiting for Customer Choice Third Invalid, Stolen Transfer Selected Confiscating Transfer Cancel Rejected Transfer Approved Ejecting Printing Receipt Printed Query Selected Query Rejected Query Approved Cash Dispensed Withdrawal Selected Withdrawal Withdrawal Approved Dispensing Rejected fsm-27 Example of hierarchical statechart Customer Input Card Inserted Startup Closed Down Closedown Insufficient Cash After (Elapsed Time) [Closedown Was Requested] After (Elapsed Time) [Closedown Not Requested] Terminating Transaction PIN entered Waiting for PIN Validating PIN Invalid PIN Cancel Third Invalid, Stolen Card Confiscated Confiscating Terminating Ejecting Card Ejected Valid PIN Waiting for Customer Choice Transfer Selected Transaction Transfer Rejected Transfer Approved Printing Receipt Printed Query Selected Withdrawal Selected Query Withdrawal Query Approved Withdrawal Approved Dispensing Cash Dispensed fsm-28 14

15 Figure Top level statechart for ATM Control Card Inserted / Get PIN Customer Input Startup Closed Down Entry / Display System Down Closedown Entry / Display Welcome Insufficient Cash / Eject After(Elapsed Time) [Closedown Requested] After(Elapsed Time)[Closedown not Requested] Third Invalid, Stolen / Confiscate,Update Status Cancel / Eject, Display Cancel Terminating Transaction Transfer Selected / Request Transfer, Query Selected / Request Query, Withdrawal Selected / Request Withdrawal, Transaction Rejected / Eject, Display Apology Transfer Approved / Print Receipt, Update Status Query Approved / Print Receipt, Update Status Withdrawal Approved / Dispense Cash, Update Status 29 Figure Statechart for ATM Control - Customer Input composite state Customer Input PIN Entered / Validate PIN Waiting for PIN Validating PIN Card Inserted / Get PIN Invalid PIN / Invalid PIN Prompt, Update Status Entry/ Display Welcome Cancel / Eject, Display Cancel Third Invalid, Stolen / Confiscate, Update Status Waiting for Customer Choice Valid PIN / Display Menu, Udt Update Statust Transfer Selected / Request Transfer, Withdrawal Selected / Request Withdrawal, Query Selected / Request Query, 30 15

16 Figure Statechart for ATM - Transaction composite state Transaction Rejected / Eject, Display Apology Transfer Selected / Request Transfer, Query Selected / Request Query, Transfer Query Transfer Approved / Print Receipt, Update Status Query Approved / Print Receipt, Update Status Withdrawal Selected / Request Withdrawal, Withdrawal Withdrawal Approved / Dispense Cash, Udt Update Statust 31 Figure Statechart for ATM Control - Terminating Transaction composite state Closed Down After(Elapsed Time)[Closedown Requested] Entry / Display System Down Entry / Display Welcome After(Elapsed Time)[Closedown not Requested] Terminating Transaction Cancel / Eject, Display Cancel Third Invalid, Stolen / Confiscate Rejected / Eject, Display Apology Card Confiscated / Display Confiscated Confiscating Terminating Ejecting Card Ejected / Display Ejected Receipt Printed / Eject Insufficient Cash / Eject Printing Transfer Approved / Print Receipt, Update Status Cash Dispensed / Query Approved / Print Receipt, Update Status Print Receipt, Display Cash Dispensed ACK Cash Dispensed Withdrawal Approved / Dispense Cash, Update Status Dispensing 32 16

17 Steps in Using COMET/UML 1 Develop Software Requirements Model 2 Develop Software Analysis Model Develop static model of problem domain (Chapter 7) Structure system into objects (Chapter 8) Develop statecharts for state dependent objects (Chapter 10) Develop object interaction diagrams for each use case (Chapter 9, 11) 3 Develop Software Design Model User 1 Requirements 2 Modeling Analysis Modeling 4 Throwaway Prototyping 3 5 Design Modeling 6 Incremental Software Construction 7 Incremental Software Integration 8 Customer Incremental Prototyping 9 15 System Testing