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Dynamic Modeling

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Wheel. Forward. Backward. Stationary. Stationary. power. on. power. off. power. off. power. on ... The temporal relationship of between objects over time ... – PowerPoint PPT presentation

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Title: Dynamic Modeling


1
Dynamic Modeling
2
Dynamic Modeling with UML
  • Interaction diagram
  • Dynamic behavior of a set of objects arranged in
    time sequence
  • Interaction between objects
  • State Chart diagram
  • A state machine that describes the response of a
    given class to the receipt of outside stimuli
  • Behavior of a single object

3
Sequence Diagram
  • From flow of events in use case, go to sequence
    diagram
  • Graphical description of objects in use case
  • Classes have already been found, but finds new
    classes
  • Each event passes a message between a sender
    object and a receiver object

4
Example
  1. Establish connection between smart card and
    onboard computer
  2. Establish connection between onboard computer and
    sensor for seat
  3. Get current seat position and store on smart card

5
Sequence Diagram for Get SeatPosition
Seat
Onboard Computer
Smart Card
1. Establish connection between smart card and
onboard computer 2. Establish connection between
onboard computer and sensor for seat 3. Get
current seat position and store on smart card
Establish Connection
Establish Connection
Accept Connection
Accept Connection
Get SeatPosition
500,575,300
time
6
Heuristics for Sequence Diagrams
  • Layout
  • 1st column Should correspond to the actor who
    initiated the use case
  • 2nd column Should be a boundary object
  • 3rd column Should be the control object that
    manages the rest of the use case
  • Creation
  • Control objects are created at the initiation of
    a use case
  • Boundary objects are created by control objects

7
  • Access
  • Entity objects are accessed by control and
    boundary objects,
  • Entity objects should never call boundary or
    control objects This makes it easier to share
    entity objects across use cases and makes entity
    objects resilient against technology-induced
    changes in boundary objects.

8
Is this a good Sequence Diagram?
Seat
Onboard Computer
Smart Card
  • First column is not the actor
  • It is not clear where the boundary object is
  • It is not clear where the control object is

Establish Connection
Establish Connection
Accept Connection
Accept Connection
Get SeatPosition
500,575,300
9
An ARENA Sequence Diagram Create Tournament
10
Impact on ARENAs Object Model
  • Lets assume, before we formulated the previous
    sequence diagram, ARENAs object model contained
    the objects
  • League Owner, Arena, League, Tournament, Match
    and Player
  • The Sequence Diagram identified new Classes
  • Tournament Boundary, Announce_Tournament_Control

11
League
League

Owner
1

Attributes
Attributes
Operations
Operations
Tournament
Attributes
Operations
Player
Match


Attributes
Attributes
Operations
Operations
12
League
League

Owner
1

Attributes
Attributes
Operations
Operations
Tournament
Attributes
Operations
Player
Match


Attributes
Attributes
Operations
Operations
13
Impact on ARENAs Object Model (ctd)
  • The Sequence Diagram also supplied us with a lot
    of new events
  • newTournament(league)
  • setName(name)
  • setMaxPlayers(max)
  • Commit
  • checkMaxTournaments()
  • createTournament

14
  • Question Who owns these events?
  • Answer For each object that receives an event
    there is a public operation in the associated
    class.
  • The name of the operation is usually the name of
    the event.

15
Example from the Sequence Diagram
createTournament is a (public) operation owned
by Announce_Tournament_Control
createTournament (name, maxp)
16
League
League

Owner
1

Attributes
Attributes
Operations
Operations
Tournament
Announce_ Tournament_ Control
Attributes
Operations
Attributes
createTournament (name, maxp)
Player
Match


Attributes
Attributes
Operations
Operations
17
What else can we get out of sequence diagrams?
  • Sequence diagrams are derived from the use cases.
    We therefore see the structure of the use cases.
  • The structure of the sequence diagram helps us to
    determine how decentralized the system is.
  • We distinguish two structures for sequence
    diagrams Fork and Stair Diagrams (Ivar Jacobsen)

18
Fork Diagram
  • Much of the dynamic behavior is placed in a
    single object, ususally the control object. It
    knows all the other objects and often uses them
    for direct questions and commands.



19
Stair Diagram
  • The dynamic behavior is distributed. Each object
    delegates some responsibility to other objects.
    Each object knows only a few of the other objects
    and knows which objects can help with a specific
    behavior.



20
Fork or Stair?
  • Which of these diagram types should be chosen?
  • Object-oriented fans claim that the stair
    structure is better
  • The more the responsibility is spread out, the
    better
  • However, this is not always true. Better
    heuristics

21
  • Decentralized control structure
  • The operations have a strong connection
  • The operations will always be performed in the
    same order
  • Centralized control structure (better support of
    change)
  • The operations can change order
  • New operations can be inserted as a result of new
    requirements

22
UML Statechart Diagram Notation
Event trigger With parameters
State1
State2
Event1(attr) condition/action
do/Activity
Guard condition
entry /action
exit/action
Also internal transition and deferred events
23
  • Notation based on work by Harel
  • Added are a few object-oriented modifications
  • A UML statechart diagram can be mapped into a
    finite state machine

24
Statechart Diagrams
  • Graph whose nodes are states and whose directed
    arcs are transitions labeled by event names.
  • We distinguish between two types of operations in
    statecharts
  • Activity Operation that takes time to complete
  • associated with states
  • Action Instantaneous operation
  • associated with events
  • associated with states (reduces drawing
    complexity) Entry, Exit, Internal Action

25
  • A statechart diagram relates events and states
    for one class
  • An object model with a set of objects has a
    set of state diagrams

26
State
  • An abstraction of the attributes of a class
  • State is the aggregation of several attributes a
    class
  • Basically an equivalence class of all those
    attribute values and links that do no need to be
    distinguished as far as the control structure of
    the system is concerned
  • Example State of a bank
  • A bank is either solvent or insolvent
  • State has duration

27
Example of a StateChart Diagram
28
Toy Car Dynamic Model
Wheel
Forward
power

power

off
on
Stationary
Stationary
power

power

on
off
Backward
29
State Chart Diagram vs Sequence Diagram
  • State chart diagrams help to identify
  • Changes to an individual object over time
  • Sequence diagrams help to identify
  • The temporal relationship of between objects over
    time
  • Sequence of operations as a response to one or
    more events
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