Dynamical enumeration in XSD

Question

I have such xml structure:

<main>
  <objects>
    <object name="book" />
    <object name="table" />
  </objects>
  <actions>
    <action input="book" />
    <action input="table" />
    <action input="book" />
  </actions>
</main>

This is a simplified example.

I want to create xsd schema which invalidates such xml:

<main>
  <objects>
    <object name="book" />
    <object name="table" />
  </objects>
  <actions>
    <action input="book" />
    <action input="table" />
    <action input="fruit" />
  </actions>
</main>

because of there is no object item with the name "fruit" into list of objects.

I can't simply create <xsd:enumeration> because object names are always different and I don't know all of them. It seems to be a list of possible values of action's names should be created dynamically.

It would be wonderful to create enumeration dynamically for IntelliSense support (<xsd:assert> can't provide it).

Is it possible?

Don't believe you can while they are attributes, except by changing the xsd each time. If input was an element, then you could use ID and IDRef, to do xml's equivalent of a "foreign key". e.g you put book and table in one element, then action has an idref attribute that must refer to an existing id — Tony Hopkinson, Jul 28 '12 at 14:40

score 3 · Accepted Answer · answered Jul 28 '12 at 16:15

Start with a generated XSD, then tweak it to introduce the constraints you want. The Intellisense part is highly dependent on the editor. Even though the metadata to infer a "smart" intellisense is in there (via key/keyref), I doubt editors in the market would make use of that. The XSD below would validate and fail the XMLs you've provided.

<?xml version="1.0" encoding="utf-8"?>
<!--XML Schema generated by QTAssistant/XML Schema Refactoring (XSR) Module (http://www.paschidev.com)-->
<xsd:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <xsd:element name="main">
        <xsd:complexType>
            <xsd:sequence>
                <xsd:element name="objects">
                    <xsd:complexType>
                        <xsd:sequence>
                            <xsd:element maxOccurs="unbounded" name="object">
                                <xsd:complexType>
                                        <xsd:attribute name="name" type="xsd:string" use="required"/>
                                </xsd:complexType>
                            </xsd:element>
                        </xsd:sequence>
                    </xsd:complexType>
                </xsd:element>
                <xsd:element name="actions">
                    <xsd:complexType>
                        <xsd:sequence>
                            <xsd:element maxOccurs="unbounded" name="action">
                                <xsd:complexType>
                                        <xsd:attribute name="input" type="xsd:string" use="required"/>
                                </xsd:complexType>
                            </xsd:element>
                        </xsd:sequence>
                    </xsd:complexType>
                </xsd:element>
            </xsd:sequence>
        </xsd:complexType>
        <xsd:key name="Objects">
            <xsd:selector xpath="objects/object"/>
            <xsd:field xpath="@name"/>
        </xsd:key>
        <xsd:keyref name="ActionToObjects" refer="Objects">
            <xsd:selector xpath="actions/action"/>
            <xsd:field xpath="@input"/>
        </xsd:keyref>
    </xsd:element>
</xsd:schema>

The diagram:

QTAssistant showing XSD diagram with key/keyref features

Dynamical enumeration in XSD

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