Issue 6873: UML 2 Super / state machines / non-existent return type (uml2-superstructure-ftf)
Source: Simula Research Laboratory (Mr. Bran Selic, selic(at)acm.org)
Nature: Uncategorized Issue
Severity: 
Summary: The LCA operation, defined in section 15.3.12 (page 194) has a non-existent return type, CompositeState
Resolution: see above
Revised Text: 
Actions taken:
December 31, 2003: received issue
March 8, 2005: closed issue
Discussion: 
In the context of the UML2.0 metamodel the LCA of two states shall be a model element
which is either a state or the region, which is the least common container of the states in
the statemachine containment hierarchy. Practically it can be either a region or an
orthogonal states as these are the only statemachine model elements that contain more
than a single element (regular states contain 0..1 region, and therefore won’t be LCAs)
This implies the following corrections to the text:
Constraint 4 on page 470 shall be modified to
[4]All transitions incoming a join vertex must originate in different regions of an orthogonal state.
(self.kind = #join)
implies
self.incoming->forAll (t1, t2 | t1<>t2 implies (self.stateMachine.LCA(t1.source, t2.source).isOrthogonal)
Constraint 6 shall be modified to:
[6] All transitions outgoing a fork vertex must target states in different regions of an orthogonal state.
(self.kind = #fork) implies
self.outgoing->forAll (t1, t2 | t1<>t2 implies
(self.stateMachine.LCA(t1.target, t2.target).isOrthogonal)
The additional operations section (p 491) shall be modified to specify the LCA function
without the OCL definition, since lacking a common metamodel element for state and
region makes the OCL specification of it too cumbersome to add any value.
Therefore the ancestor operation on page 491 shall be removed, and the LCA operation
will be defined as follows:
[1] The operation LCA(s1,s2) returns the an orthogonal state or a region which is least common ancestor of
states s1 and s2 based on the statemachine containment hierarchy.
The paragraph Transition execution sequence shall be corrected on page 501 to the
following: Every transition, except for internal and local transitions, causes exiting of a source state, and entering of
the target state.
These two states, which may be comp osite, are designated as the main source and the main target of a
transition.
The least common ancestor (LCA) of a (compound) transition is a region or an orthogonal state which is
the LCA of the source and target states of the (compound) transition. The LCA operation is an operation
defined for the statemachine class.
If the LCA is a region, then the main source is a direct subvertex of the region which contains the
source states, and the main target is a the subvertex of the region that contains the target states.
In case where the LCA is an orthogonal state, the main source and main target are the orthogonal state
itself. The reason is that transition crossing regions of an orthogonal state forces exit of the entire
orthogonal state and reentering all of its regions.
End of Annotations:=====
ubject: UML 2 Super / state machines / non-existent return type 
X-Mailer: Lotus Notes Release 6.0.2CF1 June 9, 2003 
From: Branislav Selic <bselic@ca.ibm.com> 
Date: Tue, 30 Dec 2003 09:44:49 -0500 
X-MIMETrack: Serialize by Router on D25ML05/25/M/IBM(Release 6.0.2CF1|June 9, 2003) at 
 12/30/2003 09:44:51, 
        Serialize complete at 12/30/2003 09:44:51 


The LCA operation, defined in section 15.3.12 (page 194) has a non-existent return type, CompositeState. 

Bran Selic
Distinguished Engineer
IBM Rational Software