© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 1 Advanced UML State Diagrams

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 2 Objectives  To present advanced features of the UML state diagram notation  To illustrate uses of state diagrams with advanced features  To present heuristics for making good state diagrams with advanced features

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 3 Topics  Concurrent composite states  Compound transitions  History and deep history states  More state diagram heuristics

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4 Concurrent Composite States  The regions in a concurrent composite state nested state compartment contain state diagrams that execute in parallel.  One state in each region is entered when the concurrent composite state is entered.  One state from each region is always among the joint concurrent states until the concurrent composite state is exited.  Events cause transitions in each concurrent region to occur simultaneously.

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 5 Concurrent Composite State Example

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 6 Entering Concurrent Composite States  Make a transition to the concurrent composite state boundary The initial state in each region becomes the current state  Make a transition to individual states in different regions Main transition goes to a fork bar Transitions to individual state come from the fork bar A region without a state targeted by a transition begins in its initial state

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 7 Entering Selected Concurrent States: Illustration

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 8 Leaving Concurrent Composite States  Make a transition from the concurrent composite state boundary For a non-completion transition, all concurrent sub-states are exited immediately For a completion transition, the current state must be a final state in every concurrent region  Make a transition from one or more concurrent sub-states Coordinated transitions can go to a join bar All other sub-states are exited immediately

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 9 Leaving Selected Concurrent States: Illustration

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 10 Using Concurrent Composite States  Any concurrent composite state can be represented by a diagram with only simple states, but it will have many more states than the concurrent composite state.  Concurrent composite states thus simplify diagrams.  On the other hand, diagrams with concurrent composite states are often hard to understand.

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 11 Compound Transitions  Transitions from multiple sources or to multiple targets with common transition strings Transition arrows from multiple sources may converge on a transition junction point from which a single arrow goes to a target  Common transition string stated only once A transition arrows with a single event string may end at a junction point from which emerge arrows with mutually exclusive guards to multiple targets  Symbol is a filled circle

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 12 Compound Transition Example

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 13 History States  A history state is a pseudo-state indicating that the sub-state last active when a composite state was exited should be reentered. Symbol is a circled H  Many common devices have persistent state, so this is a useful modeling feature.

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 14 History State Example

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 15 History State Restrictions  May only appear in a region of a composite state  Transitions may only enter a history state from outside the composite state  May have at most one unlabeled outgoing transition to a peer state Indicates the default reentered state if the composite state has not yet been entered  History states may not have internal transitions, nested compartments, etc.  History state is forgotten if the current inner state becomes a final state.

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 16 Deep History States  A history state indicates reentry to a state at the same nesting level. States at lower nesting levels are entered as usual (initial states).  A deep history state is a pseudo-state indicating that the states last active at every nesting level when a composite state was exited should be reentered. Symbol is a circled H*

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 17 Deep History State Example

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 18 More State Diagram Heuristics 1  Avoid concurrent composite states, especially those with synch states.  Designate an initial state in every concurrent region of a concurrent composite state.  Check that transitions to several concurrent sub-states go through a fork.

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 19 More State Diagram Heuristics 2  Check that arrows connected to transition junction points are properly labeled.  Check that at most one unlabeled arrow emanates from each history state.  Check that every sequential state diagram containing a history state has an initial state.

© 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 20 Summary  State diagrams can show concurrency concurrent composite states, but these are governed by somewhat complex rules and hard sometimes hard to understand.  Compound transitions allow combination of several transitions with common transition strings into one.  History and deep history states allow state diagrams to model persistent states.