How to do a choice on aggregation with XML schema

Discussion in 'XML' started by Sony Antony, Dec 18, 2003.

  1. Sony Antony

    Sony Antony Guest

    Hello:
    ( Please redirect me to the correct list if this is not where I m
    supposed to
    ask this question )

    Our application essentially sends xml 'commands' to another system.

    These commands are essentially one xml element signifying which
    command it is (
    3 types of commands ) and a corresponding data required by that
    command.
    Because some different teams are involved, we do not have freedom to
    change the
    XML structure ( xml vocabulary )
    XML appears in one of the following 3 forms

    <COMMAND>REQUEST1</COMMAND>
    <COMMAND_DATA>
    <REQ1_DAT1> something </REQ1_DAT1>
    <REQ1_DAT2> something </REQ1_DAT2>
    ....
    </COMMAND_DATA>

    or

    <COMMAND>REQUEST2</COMMAND>
    <COMMAND_DATA>
    <REQ2_DAT1> something </REQ2_DAT1>
    <REQ2_DAT2> something </REQ2_DAT2>
    <REQ2_DAT3> something </REQ2_DAT3>
    ....
    </COMMAND_DATA>

    or

    <COMMAND>REQUEST3</COMMAND>
    <COMMAND_DATA>
    <REQ3_DAT1> something </REQ3_DAT1>

    ....
    </COMMAND_DATA>


    We need to essentially build a schema that will restrict the xml to be
    in one
    of these 3 forms. Is it possible to do this at all.

    I had trouble defining it as the definition for COMMAND_DATA is
    changing
    depending on what the COMMAND is.

    I tried something like

    <xs:simpleType name="req1Typ">
    <xs:restriction base="xs:string">
    <xs:pattern value="REQUEST1"/>
    </xs:restriction>
    </xs:simpleType>

    <xs:simpleType name="req2Typ">
    <xs:restriction base="xs:string">
    <xs:pattern value="REQUEST2"/>
    </xs:restriction>
    </xs:simpleType>

    <xs:simpleType name="req1Typ">
    <xs:restriction base="xs:string">
    <xs:pattern value="REQUEST2"/>
    </xs:restriction>
    </xs:simpleType>

    <xs:complexType name req1DatTyp>
    <xs:sequence>
    <xs:element name="REQ1_DAT1"/>
    <xs:element name="REQ1_DAT2"/>
    ...
    <xs:sequence>
    </xs:complexType>

    <xs:complexType name req2DatTyp>
    <xs:sequence>
    <xs:element name="REQ2_DAT1"/>
    <xs:element name="REQ2_DAT2"/>
    <xs:element name="REQ2_DAT3"/>
    ...
    <xs:sequence>
    </xs:complexType>

    <xs:complexType name req3DatTyp>
    <xs:sequence>
    <xs:element name="REQ3_DAT1"/>
    ...
    <xs:sequence>
    </xs:complexType>


    <xs:complexType name="choice_on_aggregation" >
    <xs:choice>
    <xs:sequence>
    <xs:element name="COMMAND" type="req1Typ">
    <xs:element name="COMMAND_DATA" type="req1DatTyp">
    </xs:sequence>
    <xs:sequence>
    <xs:element name="COMMAND" type="req2Typ">
    <xs:element name="COMMAND_DATA" type="req1DatTyp">
    </xs:sequence>
    <xs:sequence>
    <xs:element name="COMMAND" type="req3Typ">
    <xs:element name="COMMAND_DATA" type="req1DatTyp">
    </xs:sequence>
    </xs:choice>
    </xs:complexType>

    <element name"GLOBAL" type="choice_on_aggregation"/>


    But though my xml editor ( xmlspy ) reported this to be a valid
    schema, when I
    used its 'generate sample XML' feature, it ended up generating xml
    that did not
    comply with the schema !!
    When I used xerces to validate I got an error like

    "http://www.bellsouth.com/wfaif":COMMAND and
    "http://www.bellsouth.com/wfaif":COMMAND (or elements from their
    substitution group) violate "Unique Particle Attribution". During
    validation against this schema, ambiguity would be created for those
    two particles"

    Any help will be greatly appreciated
    Thanks
    --sony
    Sony Antony, Dec 18, 2003
    #1
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  2. Sony Antony

    Sony Antony Guest

    (Sony Antony) wrote in message news:<>...
    > Hello:
    > ( Please redirect me to the correct list if this is not where I m
    > supposed to
    > ask this question )
    >
    > Our application essentially sends xml 'commands' to another system.
    >
    > These commands are essentially one xml element signifying which
    > command it is (
    > 3 types of commands ) and a corresponding data required by that
    > command.
    > Because some different teams are involved, we do not have freedom to
    > change the
    > XML structure ( xml vocabulary )
    > XML appears in one of the following 3 forms
    >
    > <COMMAND>REQUEST1</COMMAND>
    > <COMMAND_DATA>
    > <REQ1_DAT1> something </REQ1_DAT1>
    > <REQ1_DAT2> something </REQ1_DAT2>
    > ...
    > </COMMAND_DATA>
    >
    > or
    >
    > <COMMAND>REQUEST2</COMMAND>
    > <COMMAND_DATA>
    > <REQ2_DAT1> something </REQ2_DAT1>
    > <REQ2_DAT2> something </REQ2_DAT2>
    > <REQ2_DAT3> something </REQ2_DAT3>
    > ...
    > </COMMAND_DATA>
    >
    > or
    >
    > <COMMAND>REQUEST3</COMMAND>
    > <COMMAND_DATA>
    > <REQ3_DAT1> something </REQ3_DAT1>
    >
    > ...
    > </COMMAND_DATA>
    >
    >
    > We need to essentially build a schema that will restrict the xml to be
    > in one
    > of these 3 forms. Is it possible to do this at all.








    Looks like it is impossible using w3C schema
    ( http://www.w3.org/TR/xmlschema-1/#non-ambig )

    It also turns out that w3c schema is not capable of doing conditionals
    in general - like "elements a,b,c should be present if the value of
    this other element is this"

    That fells like a huge shortcoming on the expressive nature of w3c
    schema. I hear that Relax NG is capable of doing such things. But we
    dont have that liberty.

    --sony















    >
    > I had trouble defining it as the definition for COMMAND_DATA is
    > changing
    > depending on what the COMMAND is.
    >
    > I tried something like
    >
    > <xs:simpleType name="req1Typ">
    > <xs:restriction base="xs:string">
    > <xs:pattern value="REQUEST1"/>
    > </xs:restriction>
    > </xs:simpleType>
    >
    > <xs:simpleType name="req2Typ">
    > <xs:restriction base="xs:string">
    > <xs:pattern value="REQUEST2"/>
    > </xs:restriction>
    > </xs:simpleType>
    >
    > <xs:simpleType name="req1Typ">
    > <xs:restriction base="xs:string">
    > <xs:pattern value="REQUEST2"/>
    > </xs:restriction>
    > </xs:simpleType>
    >
    > <xs:complexType name req1DatTyp>
    > <xs:sequence>
    > <xs:element name="REQ1_DAT1"/>
    > <xs:element name="REQ1_DAT2"/>
    > ...
    > <xs:sequence>
    > </xs:complexType>
    >
    > <xs:complexType name req2DatTyp>
    > <xs:sequence>
    > <xs:element name="REQ2_DAT1"/>
    > <xs:element name="REQ2_DAT2"/>
    > <xs:element name="REQ2_DAT3"/>
    > ...
    > <xs:sequence>
    > </xs:complexType>
    >
    > <xs:complexType name req3DatTyp>
    > <xs:sequence>
    > <xs:element name="REQ3_DAT1"/>
    > ...
    > <xs:sequence>
    > </xs:complexType>
    >
    >
    > <xs:complexType name="choice_on_aggregation" >
    > <xs:choice>
    > <xs:sequence>
    > <xs:element name="COMMAND" type="req1Typ">
    > <xs:element name="COMMAND_DATA" type="req1DatTyp">
    > </xs:sequence>
    > <xs:sequence>
    > <xs:element name="COMMAND" type="req2Typ">
    > <xs:element name="COMMAND_DATA" type="req1DatTyp">
    > </xs:sequence>
    > <xs:sequence>
    > <xs:element name="COMMAND" type="req3Typ">
    > <xs:element name="COMMAND_DATA" type="req1DatTyp">
    > </xs:sequence>
    > </xs:choice>
    > </xs:complexType>
    >
    > <element name"GLOBAL" type="choice_on_aggregation"/>
    >
    >
    > But though my xml editor ( xmlspy ) reported this to be a valid
    > schema, when I
    > used its 'generate sample XML' feature, it ended up generating xml
    > that did not
    > comply with the schema !!
    > When I used xerces to validate I got an error like
    >
    > "http://www.bellsouth.com/wfaif":COMMAND and
    > "http://www.bellsouth.com/wfaif":COMMAND (or elements from their
    > substitution group) violate "Unique Particle Attribution". During
    > validation against this schema, ambiguity would be created for those
    > two particles"
    >
    > Any help will be greatly appreciated
    > Thanks
    > --sony
    Sony Antony, Dec 18, 2003
    #2
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  3. (Sony Antony) wrote in message news:<>...

    > Looks like it is impossible using w3C schema
    > ( http://www.w3.org/TR/xmlschema-1/#non-ambig )
    >
    > It also turns out that w3c schema is not capable of doing conditionals
    > in general - like "elements a,b,c should be present if the value of
    > this other element is this"
    >


    Suggest you pose your problem to the folks that lurk on the
    xmlschema-dev list (lists.w3c.org). There may be a workaround
    for this "constrait".

    - Finnbarr
    Finnbarr P. Murphy, Dec 19, 2003
    #3
  4. (Sony Antony) writes:

    > Our application essentially sends xml 'commands' to another system.
    >
    > These commands are essentially one xml element signifying which
    > command it is ( 3 types of commands ) and a corresponding data
    > required by that command. Because some different teams are
    > involved, we do not have freedom to change the XML structure ( xml
    > vocabulary ) XML appears in one of the following 3 forms
    >
    > <COMMAND>REQUEST1</COMMAND>
    > <COMMAND_DATA>
    > <REQ1_DAT1> something </REQ1_DAT1>
    > <REQ1_DAT2> something </REQ1_DAT2>
    > ...
    > </COMMAND_DATA>
    >
    > or
    >
    > <COMMAND>REQUEST2</COMMAND>
    > <COMMAND_DATA>
    > <REQ2_DAT1> something </REQ2_DAT1>
    > <REQ2_DAT2> something </REQ2_DAT2>
    > <REQ2_DAT3> something </REQ2_DAT3>
    > ...
    > </COMMAND_DATA>
    >
    > or
    >
    > <COMMAND>REQUEST3</COMMAND>
    > <COMMAND_DATA>
    > <REQ3_DAT1> something </REQ3_DAT1>
    >
    > ...
    > </COMMAND_DATA>


    If you want the tail end of a sequence of siblings to
    depend on the beginning, there is a very easy way to do it.
    Why not write

    <REQUEST1>
    <REQ1_DAT1> something </REQ1_DAT1>
    <REQ1_DAT2> something </REQ1_DAT2>
    ...
    </REQUEST1>

    or

    <REQUEST2>
    <REQ2_DAT1> something </REQ2_DAT1>
    <REQ2_DAT2> something </REQ2_DAT2>
    <REQ2_DAT3> something </REQ2_DAT3>
    </REQUEST2>

    etc.?

    Since you appear to have an exhaustive list of commands,
    this would appear fairly straightforward.

    Alternatively, if your collaborators insist that they
    must have the same wrapper 'COMMAND_DATA' around what
    are necessarily very different kinds of contents, you
    could write

    <COMMAND_DATA xsi:type="REQUEST1">
    <REQ1_DAT1> something </REQ1_DAT1>
    <REQ1_DAT2> something </REQ1_DAT2>
    ...
    </COMMAND_DATA>

    or

    <COMMAND_DATA xsi:type="REQUEST2">
    <REQ2_DAT1> something </REQ2_DAT1>
    <REQ2_DAT2> something </REQ2_DAT2>
    <REQ2_DAT3> something </REQ2_DAT3>
    ...
    </COMMAND_DATA>

    and define types REQUEST1, REQUEST2, etc. as restrictions
    of a more generic COMMAND_DATA type.

    If you are stuck with a vocabulary designed to fight your
    validation tools, however, and really cannot change it, all
    I can say is you have my sympathy.

    -C. M. Sperberg-McQueen
    World Wide Web Consortium
    C. M. Sperberg-McQueen, Dec 19, 2003
    #4
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