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XML Metadata Interchange — Open Issues

  • Acronym: XMI
  • Issues Count: 11
  • Description: Issues not resolved
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Issues Descriptions

XMI for TypeLibrary::Objects::Object is Unspecified

  • Key: XMI21-7
  • Legacy Issue Number: 6345
  • Status: open  
  • Source: Google ( Don Baisley)
  • Summary:

    Issue for XMI for MOF 2

    The specification of XMI for MOF 2 does not describe handling of MOF's
    object type, which is a supertype of ordinary class types as well as data
    types. Particularly, it does not describe what XML results from the
    following small example. The whole model is this:

    In a package M there is one class X having one owned attribute named Y of
    type TypeLibrary::Objects::Object with multiplicity 1..1.

    Consider the following 4 instances of X:

    1. An instance of X having Y set to the second instance of X.
    2. An instance of X having Y set to the integer 3.
    3. An instance of X having Y set to the string "this UNICODE string".
    4. An instance of X having Y set to that same fourth instance of X.

    What would an XMI-based serialization of these four instances of X look
    like?

    What would an XML schema for the package M look like?

  • Reported: XMI 1.3 — Thu, 4 Sep 2003 04:00 GMT
  • Updated: Wed, 11 Mar 2015 11:11 GMT

ISSUE: XMI for MOF 2 should address models, not just metamodels

  • Key: XMI21-9
  • Legacy Issue Number: 6635
  • Status: open  
  • Source: Google ( Don Baisley)
  • Summary:

    The XMI for MOF 2 specification has not been updated to reflect one of the key goals in the alignment of MOF 2 with UML 2, which is that XMI becomes applicable to UML class models in general rather than to MOF-based metamodels only.

    Recommended Resolution: Replace "metamodel" with "model" in most places within the XMI for MOF 2 specification. Also, in describing the mapping from classes, properties, etc. to XML, do not use wording that implies a restriction to a MOF context except where MOF is , such as for elements of the MOF Type Library.

  • Reported: XMI 1.3 — Thu, 20 Nov 2003 05:00 GMT
  • Updated: Wed, 11 Mar 2015 11:11 GMT

ISSUE: XMI for MOF 2 does not reflect MOF 2 model

  • Key: XMI21-11
  • Legacy Issue Number: 6636
  • Status: open  
  • Source: Google ( Don Baisley)
  • Summary:

    The XMI for MOF 2 Specification seems to have been written as if referring to a MOF 1 Specification. For example, it defines mappings and mapping parameters for AssociationEnd, which is not in MOF 2.

    Recommended Resolution: Restate the XMI rules and mapping parameters in terms of MOF 2 and UML 2.

  • Reported: XMI 1.3 — Thu, 20 Nov 2003 05:00 GMT
  • Updated: Wed, 11 Mar 2015 11:11 GMT

XMI for MOF 2 defines tagged values

  • Key: XMI21-10
  • Legacy Issue Number: 6394
  • Status: open  
  • Source: Google ( Don Baisley)
  • Summary:

    The XMI for MOF 2 specification defines several tagged values for adding
    data to a UML model that guide generation of an XML Schema and that guide
    document production. But these tags appear to be defined as if for MOF 1.
    To be appropriate for MOF 2 these must be defined using either an extension
    to the MOF or UML core models (as a package that adds to MOF and/or UML
    infrastructure) or they must be defined as a UML 2 profile. In either case,
    an official XML rendering of the model or profile is required. And given
    the big change from MOF 1, an example of such tags as they would appear in
    an XMI-based XML document of an example model would be very helpful.

  • Reported: XMI 1.3 — Thu, 30 Oct 2003 05:00 GMT
  • Updated: Wed, 11 Mar 2015 11:11 GMT

Are xlinks legal?

  • Key: XMI21-19
  • Legacy Issue Number: 6054
  • Status: open  
  • Source: Zuehlke Engineering ( Frank Pilhofer)
  • Summary:

    maybe this is just because of my ignorance, but I'm running into
    a problem trying to validate documents against an XMI based schema
    here, and it looks like the validator has a point.

    As usual, my base document is XMI 2.0, formal/03-05-02.

    Section 1.10.2 "Linking" describes the usage of XLink simple links
    and XPointers to link across documents.

    However, looking at the schema production rules (page 2-2 to 2-5,
    rules 4g:ClassAttListItems and 1g:XMIFixedAttribs, as well as the
    LinkAttribs attributeGroup in the Fixed Schema Declarations on
    page 2-10, the xlink:href is never declared as a legal attribute
    for complexTypes.

    Hence I see why the parser (Xerces-C, when requested to validate)
    complains about attempts to use XLinks in a document.

    I think it is paramount that documents validate against the schema.
    (Am I the first to attempt validation? Can't be.)

    I realize that there doesn't seem to be a schema for XLinks yet,
    so the short-term solution might be to allow the "normal" href
    attribute to contain an XPointer.

    As a minor nitpicking, page 1-23 gives the XLink namespace as
    "http://www.w3.org/1999/XLink", whereas the W3C recommendation
    for XLink uses "http://www.w3.org/1999/xlink" (note case).

  • Reported: XMI 1.3 — Wed, 13 Aug 2003 04:00 GMT
  • Updated: Fri, 6 Mar 2015 20:59 GMT

Remarks to chapter "3.4.3 Derived Types and References" in XMI Spec. , v 2

  • Key: XMI21-20
  • Legacy Issue Number: 6065
  • Status: open  
  • Source: Anonymous
  • Summary:

    Remarks to chapter "3.4.3 Derived Types and References" in XMI Spec. , v 2.0, S. 3-15
    There it says:

    "... An instance of Company can use xsi:type to
    indicate that its HQAddress is actually of type USAddress and includes a zipcode:
    <Company xmi:id="Company_1" name="Acme">
    <HQAddress xmi:type="USAddress" xmi:id="Address_1"
    Street="Side Street" City="Hometown" zipcode="90210"
    ... "
    The 'HQAdress'-Element has a 'xmi:type'-Attribute. Parsing this with Xerces 2.4.0 gives problems, since a 'xsi:type' Attribute is required. Derived types must be specified with the 'xsi:type'-Attibute. Maybe the line
    "... An instance of Company CAN use xsi:type ..."
    should be changed in
    " ... An instance of Company MUST use xsi:type ..."

  • Reported: XMI 1.3 — Wed, 13 Aug 2003 04:00 GMT
  • Updated: Fri, 6 Mar 2015 20:59 GMT

Schema production rule for 'ClassReferences' (4.e)

  • Key: XMI21-17
  • Legacy Issue Number: 6010
  • Status: open  
  • Source: TU Braunschweig ( Lorenz Däubler)
  • Summary:

    The Schema production rule for 'ClassReferences' (4.e) does not conform with the Document Production Rule 'Reference Element' (4). In the Class References the linking attribues are missing

  • Reported: XMI 1.3 — Mon, 21 Jul 2003 04:00 GMT
  • Updated: Fri, 6 Mar 2015 20:59 GMT


XMI 2.0 issue: Proxies and Multiplicities

  • Key: XMI21-12
  • Legacy Issue Number: 5950
  • Status: open  
  • Source: Zuehlke Engineering ( Frank Pilhofer)
  • Summary:

    Doc references are based on formal/03-05-02.

    In a Schema that is produced by the XML Schema Production
    rules, enforcement of multiplicities is incompatible with
    the use of proxies.

    According to 1.10.1, page 1-21, "Elements act as a union,
    where they are either a definition or a proxy. Proxies use
    the LinkAttribs attribute group to define the link, and
    contain no nested elements."

    However, if the org.omg.xmi.enforceMinimumMultiplicity is
    true, then the generated schema does not allow the complex-
    Type's content to be empty, and so proxies cannot exist in
    an XML document.

    As a simple fix, the 4b:ClassContents could be wrapped into
    an additional choice element, as in

    <xsd:choice minOccurs="0">
    <xsd:sequence>
    4b:ClassContents
    </xsd:sequence>
    </xsd:choice>

    This would allow the element to be empty. However, in this
    form, an XML document that contained both link attributes
    and contents would still validate.

    A stronger solution would be to make a choice between a
    link element and contents, by removing the LinkAttribs from
    the ObjectAttribs attribute group and by, in rule set 4,
    defining something along the lines of

    <xsd:choice>
    <xsd:sequence>
    4b:ClassContents
    </xsd:sequence>
    <xsd:element name="href" type="xsd:string">
    <xsd:element name="idref" type="IDREF">
    </xsd:choice>

    This way, an element in a validating document could only be
    either a proxy or not.

    As a side note to this issue, there are obviously unpleasant
    side effects when org.omg.xmi.enforceMinimumMultiplicity is
    true and org.omg.xmi.element is false. org.omg.xmi.enforce-
    MinimumMultiplicity=true should have the same effect as
    if org.omg.xmi.element=true and org.omg.xmi.attribute=false.

  • Reported: XMI 1.3 — Thu, 12 Jun 2003 04:00 GMT
  • Updated: Fri, 6 Mar 2015 20:59 GMT

More type safety in generated schemas

  • Key: XMI21-14
  • Legacy Issue Number: 5981
  • Status: open  
  • Source: Zuehlke Engineering ( Frank Pilhofer)
  • Summary:

    Document refs are against formal/03-05-02.

    According to rule 4d of the Schema production rules on page 2-5,
    "The type is 'xsd:string' for simple attributes".

    I assume here that "simple attributes" refers to MOF primitive
    types (Boolean, Integer, Long, Float, Double, String).

    I wonder why xsd:string was used for all these primitive types,
    when perfectly suitable data types are predefined for XML Schemas:
    there's xsd:boolean, xsd:int, xsd:long, xsd:float and xsd:double
    that exactly match the data types used by MOF.

    I propose to make use of these existing types to strengthen the
    generated schema.

  • Reported: XMI 1.3 — Mon, 23 Jun 2003 04:00 GMT
  • Updated: Fri, 6 Mar 2015 20:59 GMT

Schema production rule 4d clarification request

  • Key: XMI21-13
  • Legacy Issue Number: 5975
  • Status: open  
  • Source: Zuehlke Engineering ( Frank Pilhofer)
  • Summary:

    Document refs are against formal/03-05-02.

    Maybe it's because I'm still struggling with the details
    of XML Schemas and MOF, but I'm confused with rule 4d of
    the XML Schema Production rules (EBNF on page 2-4, expla-
    nation on page 2-5).

    • According to the EBNF, a type='xmi:Any' is an output
      option, but according to the explanation, this option
      is never used.
    • The explanation goes, "The type is 'xsd:string' for simple
      attributes ..." It is not clear to me what constitutes a
      "simple" vs. "non-simple" attributes. I assume this refers
      to MOFs PrimitiveTypes, but in any case a clarification
      would be useful.
    • The explanation goes on, "The type is [...] part of the
      of the value of the org.omg.xmi.schemaType tag". Why does
      it say "part of"? What should be removed from the value?
    • There is also a question of precedence. I guess the
      intention is that the schemaType tag should take
      precedence over the "simple attribute" decision?
    • There is no "else:" What if the attribute is not simple,
      not an enumeration, and the schemaType tag is not set?
      (Or maybe that is not possible in MOF?)
  • Reported: XMI 1.3 — Mon, 23 Jun 2003 04:00 GMT
  • Updated: Fri, 6 Mar 2015 20:59 GMT