I have also transitioned away from defining element references to defining complex types and only one global element on my own, so I agree completely with these best practices.
You've recommended that DFDL schemas should use elementFormDefault="unqualified" in the style guide without giving a reason for it. Can you please expand that one sentence to include your rationale, such as that the XML instance document would become larger because every single element in it would have a prefix even when all the elements are already in the same target namespace? Interestingly enough, I was experimenting with the ex_nums.dfdl.xsd schema a while ago when testing it with the C code generator and I happened to change it to use elementFormDefault="qualified", targetNamespace="http://example.com";, and xmlns="http://example.com"; all together. I found out that the combination of these 3 attributes together was the secret sauce to outputting the simplest XML instance document yet: <ex_nums xmlns="http://example.com";> <array> ... </fixed> </ex_nums> The root element had an xmlns attribute and no prefix. No other elements had either an xmlns attribute or a prefix. Normally, a schema uses both a target namespace and a prefix, and the XML instance document ends up looking like: <ex:ex_nums xmlns:ex="http://example.com";> <array> ... </fixed> </ex:ex_nums> Which is not too bad, and I'm sure that makes it easier to combine elements from multiple schemas with different target namespaces and prefixes in the same XML instance document. The magic combination above probably works only for a single example schema and its instance document and can't scale to large schemas. If you try the magic combination but change xmlns="http://example.com"; to xmlns:ex="http://example.com";, you go from the smallest XML instance document to the largest XML instance document: <ex:ex_nums xmlns:ex="http://example.com";> <ex:array> ... </ex:fixed> </ex:ex_nums> Every single element gets a prefix, so that's probably your reason for recommending elementFormDefault="unqualified". John From: Mike Beckerle <[email protected]> Sent: Monday, February 13, 2023 9:41 AM To: [email protected] Subject: EXT: Page on DFDL Schema Style Guidance Comments are welcome https://cwiki.apache.org/confluence/display/DAFFODIL/DFDL+Schema+Style+Guide Mike Beckerle Apache Daffodil PMC | http://daffodil.apache.org/ OGF DFDL Workgroup Co-Chair | http://www.ogf.org/ogf/doku.php/standards/dfdl/dfdl Owl Cyber Defense | http://www.owlcyberdefense.com/
