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It appears to be a common practice when, if you have a schema which includes
a volatile code-list (enumeration), to externalise it into its own
[chameleon] schema and then include that schema into the main [transaction]
schema. I just wanted to see whether others have experience of using this
approach and if any issues arise from it ?
In our case the enumerated values of of type xs:string (not sure if this
matters but it might)
We also get our schema from a standards body who define the standard market
values. Naturally :-) my business colleagues are not always satisfied with
that and want to both extend and restrict the values used. So in this case I
am thinking of :-
a. creating another schema to contain OUR custom enum values
b. creating another schema that imports my custom codes and the market
standard and :-
- contains a type which is a restriction of the market standard enum
- contains a type which is a union of the restricted market standard and
custom enum.
Does this seems reasonable ? here's a rough example using the oft described
'currency code' example :-
Market Standard Schema (BaseCodes.xsd)
===============
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema";
elementFormDefault="qualified" version="1.0">
<xs:simpleType name="iso3currency">
<xs:annotation>
<xs:documentation>ISO-4217 3-letter currency codes. Only a subset are
defined here.</xs:documentation>
</xs:annotation>
<xs:restriction base="xs:string">
<xs:length value="3"/>
<xs:enumeration value="AUD"/>
<xs:enumeration value="BRL"/>
<xs:enumeration value="CAD"/>
<xs:enumeration value="CNY"/>
<xs:enumeration value="EUR"/>
<xs:enumeration value="GBP"/>
<xs:enumeration value="INR"/>
<xs:enumeration value="JPY"/>
<xs:enumeration value="RUR"/>
<xs:enumeration value="USD"/>
</xs:restriction>
</xs:simpleType>
</xs:schema>
My Custom Schema (MYCurrencyCodes.xsd)
============
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema";
xmlns="http://www.someorg.com/ws/2006/02/codelists";
targetNamespace="http://www.someorg.com/ws/2006/02/codelists";
elementFormDefault="qualified" attributeFormDefault="unqualified">
<xs:simpleType name="iso3currency">
<xs:restriction base="xs:string">
<xs:length value="3"/>
<xs:enumeration value="abc"/>
<xs:enumeration value="def"/>
<xs:enumeration value="ghi"/>
<xs:enumeration value="jkl"/>
<xs:enumeration value="mno"/>
<xs:enumeration value="pqr"/>
<xs:enumeration value="stu"/>
<xs:enumeration value="vwx"/>
<xs:enumeration value="yza"/>
</xs:restriction>
</xs:simpleType>
</xs:schema>
The schema to INCLUDE in the main transaction (CombinedCurrencyCodes.xsd)
=============================
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema";
xmlns:my="http://www.someorg.com/ws/2006/02/codelists";
elementFormDefault="qualified" attributeFormDefault="unqualified">
<xs:include schemaLocation="BaseCodes.xsd"/>
<xs:import namespace="http://www.someorg.com/ws/2006/02/codelists";
schemaLocation="MYCurrencyCodes.xsd"/>
<xs:simpleType name="iso3currencyRestricted">
<xs:restriction base="iso3currency">
<xs:enumeration value="CNY"/>
<xs:enumeration value="EUR"/>
<xs:enumeration value="GBP"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="MYiso3currency">
<xs:union memberTypes="iso3currencyRestricted my:iso3currency"/>
</xs:simpleType>
</xs:schema>
The main schema
===========
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema";
xmlns="urn:www.polaris-uk.co.uk/codelist/example"
targetNamespace="urn:www.polaris-uk.co.uk/codelist/example"
elementFormDefault="qualified">
<xs:include schemaLocation="CombinedCurrencyCodes.xsd"/>
<xs:element name="accountSummary">
<xs:complexType>
<xs:sequence>
<xs:element ref="timestamp"/>
<xs:element ref="currency"/>
<xs:element ref="balance"/>
<xs:element ref="interest"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="timestamp" type="xs:dateTime"/>
<xs:element name="currency" type="MYiso3currency"/>
<xs:element name="balance" type="xs:decimal"/>
<xs:element name="interest">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:decimal">
<xs:attribute name="rounding" type="roundingDirection" use="required"/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<xs:simpleType name="roundingDirection">
<xs:annotation>
<xs:documentation>Whether the interest is rounded up, down, or to the
nearest round value.</xs:documentation>
</xs:annotation>
<xs:restriction base="xs:string">
<xs:enumeration value="up"/>
<xs:enumeration value="down"/>
<xs:enumeration value="nearest"/>
</xs:restriction>
</xs:simpleType>
</xs:schema>
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