Question

So I have one RelaxNG schema that references another:

<define name="review">
  <element name="review">
    <externalRef href="other.rng"/>
  </element>
</define>

other.rng:

<start>
  <choice>
    <ref name="good"/>
    <ref name="bad"/>
  </choice>
</start>

<define name="good"> 
  <element name="good"/>
</define>

<define name="bad">
  <element name="bad"/>
</define>

Is there any way I can import only <good>, but not allow <bad>? The goal being:

<review><good/></review>: valid
<review><bad/></review>: invalid

Answer 1

The grammar you import with externalRef can’t be modified. To achieve the kind of validation you’re after, I see this method :

<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
    datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">
    <include href="other.rng">
        <start combine="choice">
            <ref name="review"/>
        </start>
    </include>
    <define name="review">
        <element name="review">
            <ref name="good"/>
        </element>
    </define>
</grammar>

• You include the other schema.
• You override the start element in the include (good and bad elements won’t be possible root).
  The specification says :

If the include element has a start component, then all start
components are removed from the grammar element.

• You make a reference to the good element in your review definition.