VODML in VOTABLE Syntax

Pros Schema changes are small and easily expressed Might have fewest delays getting going Allows “naïve” users to know that certain elements are GROUPed, even without the VODML specifics Well-defined (unambiguous)

Cons Semantics often depend on context – Can contribute to errors in serialization/deserialization – More validation needed in logic instead of syntax – GROUP heavily overloaded – Context determined in leaf nodes, so whole element needs to be read to get semantics. 4 legacy VOTABLE elements can now contain VODML element

Parser Sees a GROUP… Does it define VODML object(s)? – If VODML is first child element Does it define an attribute of another instance? – If VODML has ROLE Is it a single instance or a template for creating an instance per table row? – If any leaf node has a FIELDref, then it is a template

Validation Some simple validations not checked by syntax. – VODML can have ROLE, TYPE or both. Is it correct in context? Does PARAM name match DM attribute name? Do we care? If not, they are inconsistent.