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  1. OMG Issue

OCL23 — OCL 2.1 11.2.3 Navigated Implicit Conversion to Collection Literal

  • Key: OCL23-28
  • Legacy Issue Number: 15009
  • Status: closed  
  • Source: Model Driven Solutions ( Dr. Edward Willink)
  • Summary:

    The Issue 14981 considered use of explicit null as a Collection.

    11.2.3 states that 'If the source is the null literal, it is implicitly converted to Bag{}'.

    Surely when the null arises as a navigation result, the isOrdered and isUnique characteristics of the navigated property should determine what CollectionKind the null result is converted to?

    However meta-modelling tools and meta-modellers pay little attention to the isUnique and isOrdered characteristics of zero and unit multiplicity properties. Using this overlooked information may cause surprises.

  • Reported: OCL 2.2 — Fri, 29 Jan 2010 05:00 GMT
  • Disposition: Resolved — OCL 2.3
  • Disposition Summary:

    7.6.3 Navigation over Associations with Multiplicity Zero or One suggests non-collection are converted to Sets. Similarly 7.6.5, 9.7. So there is a contradiction in the normative conversion to Set or Bag. Set seems more sensible and what the non-normative clauses suggest.
    Using the accidental ordered/unique attributes of non-collections would lead to horrible surprises for existing usage, so it must be conversion to a set.
    Since the conversion of null yields an empty set, whereas any other object yields a single element set, the Set size is data dependent and so must be determined at run-time and cannot be expressed as a CollectionLiteralExp. Rather, evaluation of PropertyCallExp and OperationCallExp must detect a mismatch between a non-collection source type and a collection-type referredOperation class.
    Delayed resolution is inconsistent with OCL's static typing, so let us make it explicit by defining OclAny::oclAsSet() for the static analysis to invoke and perform the conversion. The conversion is represented as a regular OperationCallExp in the AST and only type-dependent run-time decisions need to be made.
    Note that the revisions below do not address the deficiencies in the normative Clause 9 text raised by Issue 15790. We continue to rely on the final sentence of 9.7: "The mapping is not formally defined in this document but should be obvious."

  • Updated: Fri, 6 Mar 2015 20:58 GMT