  Multiword expressions (MWEs) exhibit both regular and idiosyncratic
properties. Their idiosyncrasy requires lexical encoding in parallel with their
component words. Their (at times intricate) regularity, on the other hand,
calls for means of flexible factorization to avoid redundant descriptions of
shared properties. However, so far, non-redundant general-purpose lexical
encoding of MWEs has not received a satisfactory solution. We offer a proof of
concept that this challenge might be effectively addressed within eXtensible
MetaGrammar (XMG), an object-oriented metagrammar framework. We first make an
existing metagrammatical resource, the FrenchTAG grammar, MWE-aware. We then
evaluate the factorization gain during incremental implementation with XMG on a
dataset extracted from an MWE-annotated reference corpus.
