XSD question - relationship between attributes?

[Stewart Johnson]

Hey All -

I'm stuck while trying to write a schema, hoping someone can provide me
with a flash of inspiration.

One of the elements I'm writing has two attributes, both of which are
optional. I want to express in the schema that there's a relationship
between the two -- that the second attribute is optional only if the
first one is not specified. ie:

<myElement /> <!-- valid -->
<myElement name="A" /> <!-- valid -->
<myElement myattr="true" /> <!-- invalid because name wasn't specified
-->
<myElement myattr="true" name="A" /> <!-- valid -->

So far my schema looks like this:

<element name="myElement">
<complexType>
<attribute name="name" type="string" use="optional" />
<attribute name="myattr" type="boolean" use="optional"
default="false" />
</complexType>
</element>


That captures the default values and the optional nature of the two
elements, but it doesn't capture the relationship between the two. Is
there any xsd construct I can use to express the relationship? I know
how to do it with elements (xsd:group, xsd:choice) but not with
attributes.

Thanks for any thoughts.

Stewart

 

[Martin Honnen]

Stewart Johnson wrote:

I'm stuck while trying to write a schema, hoping someone can provide me
with a flash of inspiration.

One of the elements I'm writing has two attributes, both of which are
optional. I want to express in the schema that there's a relationship
between the two -- that the second attribute is optional only if the
first one is not specified. ie:

<myElement /> <!-- valid -->
<myElement name="A" /> <!-- valid -->
<myElement myattr="true" /> <!-- invalid because name wasn't specified
-->
<myElement myattr="true" name="A" /> <!-- valid -->

So far my schema looks like this:

<element name="myElement">
<complexType>
<attribute name="name" type="string" use="optional" />
<attribute name="myattr" type="boolean" use="optional"
default="false" />
</complexType>
</element>


That captures the default values and the optional nature of the two
elements, but it doesn't capture the relationship between the two. Is
there any xsd construct I can use to express the relationship? I know
how to do it with elements (xsd:group, xsd:choice) but not with
attributes.

I don't think that a W3C XML schema can express such constraints between
attributes. Other schema languages are more powerful in that regard, for
instance schematron should allow that.

 

[Stone]

Stewart Johnson wrote:



I don't think that a W3C XML schema can express such constraints between
attributes. Other schema languages are more powerful in that regard, for
instance schematron should allow that.

Hi,

I don't think you can do it using attributes. But you can express it
using elements : use a <xs:choice> within a <xs:sequence>