Path: utzoo!yunexus!geac!syntron!jtsv16!uunet!husc6!bloom-beacon!zermatt.lcs.mit.EDU!RWS
From: RWS@zermatt.lcs.mit.EDU (Robert Scheifler)
Newsgroups: comp.windows.x
Subject: XCompose structure
Message-ID: <19881011193952.8.RWS@KILLINGTON.LCS.MIT.EDU>
Date: 11 Oct 88 19:39:00 GMT
Article-I.D.: KILLINGT.19881011193952.8.RWS
References: <16645@shemp.CS.UCLA.EDU>
Sender: daemon@bloom-beacon.MIT.EDU
Organization: The Internet
Lines: 3

It is a "hook".  There is no support in R3.  Some individual companies
have done something with it, but there is currently (unfortunately) no
standard definition of how it should work.