References

The CommsDSL allows references to fields or other definitions in order not to duplicate information and avoid various copy/paste errors. The referenced element must be defined (if in the same file) or processed (if in different schema file) before the definition of the referencing element.

For example, message defines its payload as a reference (alias) to the globally defined field. This field is defined before the message definition. the opposite order must cause an error. It allows easy avoidance of circular references.

<?xml version="1.0" encoding="UTF-8"?>
<schema ...>
    <fields>
        <int name="SomeField" type="uint8" />
    </fields>

    <message name="SomeMessage" id="1">
        <ref field="SomeField" />
    </message>
</schema>

When referencing a field or a value defined in a namespace (any namespace, not just different one), the former must be prefixed with a namespace(s) name(s) separated by a . (dot).

<?xml version="1.0" encoding="UTF-8"?>
<schema ...>
    <ns name="myns">
        <fields>
            <int name="SomeField" type="uint8" />
        </fields>

        <ns name="subns">
            <fields>
                <int name="SomeOtherField" type="uint16" />
            </fields>
        </ns>

        <message name="SomeMessage" id="1">
            <ref field="myns.SomeField" />
            <ref field="myns.subns.SomeOtherField" />
        </message>
    </ns>
</schema>