Dear Moose-icians, I'm currently pondering on the idea of writing a Perl module for bibliographic records using the MODS format (http://loc.gov/mods). Basically there are two approaches I'm considering right now: a) Using XML::Compile::Schema for parsing and writing the XML records and utilizing the "typemap" feature to map the structural elements to Perl classes (probably without using Moose there). b) Using PRANG to parse/write the XML records and map their elements directly to Moose-based Perl classes.
There are a few minor questions related to b) - regarding, e.g., the handling of attributes belonging to different namespaces - which can probably be sorted out - read: expect more mails to come ;-) One questions, however, currently looks like a major road block to me - but that might be just me being ignorant of the appropriate features of Moose: The MODS specification has seen a number of revisions already where elements and attributes have been added, removed, declared (no longer) mandatory, or where the list of allowed values has been changed. My goal would be to support a number of older versions and all future versions with minimum effort. Writing the perl classes "by hand" I'd require a version attribute and write custom code in every class / accessor to check for (version-specific) correct data. But how am I supposed to tackle this problem using Moose/PRANG? Changing the 'isa' property of Moose attributes at runtime based on the value of another attribute (holding the MODS version number) seems weird. I'd be glad if someone could describe possible solutions and/or point to existing code solving this kind of problem. Thanks! Heiko
