[DFDL-WG] Numbers with multiple ranges

6 Mar 2009

      One of the existing non-XML parsers from IBM is capable of modelling an 
integer or decimal with non-contiguous ranges, eg, 0-100, 200-300, 
400-500.  It is also possible to model this using XML Schema, using a 
user-defined simple type which is a union of simple type restrictions. 

However it is not possible to model this in DFDL because unions are not 
supported. A choice could be used, but that would give different named 
elements in the resultant infoset depending on the value, which is not 
ideal.

I believe this is use case that we should consider for DFDL 1.0.  We could 
decide to allow unions, but with a constraint that the members of the 
union had to be restrictions of the same built-in type, and that clashing 
DFDL properties on the members was an error. I believe the existing 
scoping rules for visiting types would still apply ok. No annotation 
appears on the xs:union only on the xs:simpleType as currently. The net 
effect is that our parsing rules are the same as currently, but we gain 
validation capability.

I am not in favour of more widespread support for unions. I don't have a 
compelling use case for union of different logical types, eg, xs:dateTime 
and xs:string.

Your thoughts are welcome.

  !-- integer range 0 - 100
  <xsd:simpleType name="intRange1">
    <xsd:restriction base="xsd:int">
      <xsd:maxInclusive value="100"/>
      <xsd:minInclusive value="0"/>
    </xsd:restriction>
  </xsd:simpleType>

  !-- integer range 200 - 300
  <xsd:simpleType name="intRange2">
    <xsd:restriction base="xsd:int">
      <xsd:maxInclusive value="300"/>
      <xsd:minInclusive value="200"/>
    </xsd:restriction>
  </xsd:simpleType>

  !-- integer range 400-500
  <xsd:simpleType name="intRange3">
    <xsd:restriction base="xsd:int">
      <xsd:maxInclusive value="500"/>
      <xsd:minInclusive value="400"/>
    </xsd:restriction>
  </xsd:simpleType>

  !-- Union of above types
  <xsd:simpleType name="intRange">
    <xsd:union memberTypes="intRange1 intRange2 intRange3"/>
  </xsd:simpleType>

  !-- Union of anonymous types being restrictions of above types
  <xsd:simpleType name="intRangeLocal">
    <xsd:union>
      <xsd:simpleType>
        <xsd:restriction base="intRange1"/>
      </xsd:simpleType>
      <xsd:simpleType>
        <xsd:restriction base="intRange2"/>
      </xsd:simpleType>
      <xsd:simpleType>
        <xsd:restriction base="intRange3"/>
      </xsd:simpleType>
    </xsd:union>
  </xsd:simpleType>

  !-- Union of anonymous types being local restrictions
  <xsd:simpleType name="intRangeLocalRestrictions">
    <xsd:union>
      <xsd:simpleType>
        <xsd:restriction base="xsd:int">
          <xsd:minInclusive value="0"/>
          <xsd:maxInclusive value="100"/>
        </xsd:restriction>
      </xsd:simpleType>
      <xsd:simpleType>
        <xsd:restriction base="xsd:int">
          <xsd:minInclusive value="200"/>
          <xsd:maxInclusive value="300"/>
        </xsd:restriction>
      </xsd:simpleType>
      <xsd:simpleType>
        <xsd:restriction base="xsd:int">
          <xsd:minInclusive value="400"/>
          <xsd:maxInclusive value="500"/>
        </xsd:restriction>
      </xsd:simpleType>
    </xsd:union>
  </xsd:simpleType>

Regards

Steve Hanson
Programming Model Architect
WebSphere Message Brokers
Hursley, UK
Internet: smh@uk.ibm.com
Phone (+44)/(0) 1962-815848

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