Advanced LDDTool Techniques

There are some advanced techniques available via the <Ingest_LDD> document and the LDDTool that might be useful in some complex cases. On the whole, SBN recommends that you resort to these only when there are compelling reasons to do so. These features are the more experimental, and thus more unstable, parts of the package.

Schematron Rules

Schematron rules can be used to check the sort of contingency relationships (i.e., "If A, then B") that XML Schema is not particularly good at. PDS also uses Schematron to define enumerated value lists rather than XML Schema largely for the diagnostic benefits - we can include the list of valid values in the Schematron error message.

Schematron rules are applied to an XML document via a two-step process involving style sheet translations (XSL). There are some subtleties to how and when Schematron rules are triggered, so if you're going to start writing Schematron rules yourself you should take some time to become familiar with the details of the standard. There are also multiple forms of the standard with a couple of significant differences in capabilities for the more advanced Schematron programmer. PDS requires ISO Schematron, which is available as a "Publicly Available Standard" (i.e., free if you promise to behave yourself) from this ISO website: http://standards.iso.org/ittf/PubliclyAvailableStandards. Search for "Schematron".

A limited capability to define additional Schematron rules as part of LDDTool processing is provided via the <DD_Rule> class. DD_Rule classes may be added after the <DD_Class> definitions in your <Ingest_LDD> document. Details for filling out the class are on the Filling Out the DD_Rule Class page.