ALF 1.0b2 FTF Avatar
  1. OMG Issue

ALF — Enforcement of multiplicity

  • Key: ALF-6
  • Legacy Issue Number: 4907
  • Status: closed  
  • Source: International Business Machines ( Mr. Sridhar Iyengar)
  • Summary:

    [Sridhar Iyengar] 20. In a number of places in the spec (see Page 2-261,
    para 3 for an example, Page 2-266 314 next to last paragraph...) , the
    following statement 20. In a number of places in the spec (see Page
    2-appears "The semantics of adding a value that violates the
    multiplicity of an attribute is undefined". Why did the submitters not
    choose to treat this event as a violation of well formedness rules and
    raise an exception (for example by invoking an exceptionAction)? For
    vendors that implement UML tools that implement these constraints, it
    would be better if the semantics of actions handles these violations
    consistently. At some point in time when enough tools implement the
    Action Semantics spec issues such as these will become more important
    for interoperability reasons. Imagine a programming language interface
    (MOF 2 IDL or JMI) used to manipulate a UML metamodel server which has
    been extended to support the Actions package. It would be good if
    conformant client implementations treated multiplicity violations
    consistently. (the fact that the spec leaves this undefined is one way
    to be consistent I suppose!). Should the spec reviewer assume that for
    those parts of the spec where the semantics is explicitly marked as
    undefined, we should raise a red flag for modelers using these
    capabilities because those models 'may not be executable'?

    See also Page 2-266, next to last para. 'creating a link that violates
    20. In a number of places in the spec (see Page 2-maximum multiplicities
    has undefined semantics'.. 'modeler must determine when minimum
    multiplicity associations should be enforced'. There isn't a standard
    way (I know of), this can be done consistently in UML. May be this will
    get sorted out as part of UML2 as part of the OCL Metamodel RFP.

    Multiplicity constraints are very popular in UML and we should look at
    providing some clear guidelines of when and how these (and other
    constraints) are checked or ignored in UML.

    Finally in Page 128 of revised submission the following text "When a
    semantic variation point' is mentioned.

    24. ClearAssociationAction class. I suggest that handling
    multiplicity be a semantic variation point as opposed to making the
    arbitrary choice that minimum muliplicity be violated when links of the
    association in which the object participats is destroyed.This could for
    example be handled by tags that can be customized (preferably at the
    package level) to (a) ignore multiplciity constraints (b) enforce them
    and raise an exception if the constraint is violated. I did notice the
    the choice to ignore minimum multiplicity is being consistently made -
    so this will minimize confusion.

  • Reported: ALF 1.0a — Tue, 5 Mar 2002 05:00 GMT
  • Disposition: Resolved — ALF 1.0b1
  • Disposition Summary:


  • Updated: Fri, 6 Mar 2015 20:57 GMT