slightly more standard data merge: Symtax.merge (K true) avoids equality on abstract type Pretty.T and gracefully accepts overriding, Symtab.join prefers first entry as usual;
Major:
Complete pgip_types: add PGML and objtypes
Complete pgip_markup: provide markup abstraction for parsing.ML
Minor:
cleanups: signatures & structures, concrete types in XML attrs, etc.
further tests in pgip_tests.ML