[developers] code changes to LKB and [incr tsdb()]

[Stephan Oepen]

well, it turns out this cafe stays open a little longer tonight.  here
is a brief summary of recent code changes in the LKB:

  - allow customization of post-generation string read-out: when bound,
    the new global *gen-extract-surface-hook* will be invoked on edges
    returned from generation; the function must return a string which
    will be recorded in the (new) `string' slot on edges.  see the ERG
    `user-fns.lsp' for an (relatively un-appealing) example.

  - new MRS comparison functions, intended to replace the restrictive
    mrs-equalp(). 

  - eliminate unnecessary combinatorics in selectively-unpack-edges(),
    i.e. only put new indices on agenda that are actually required.

  - support to serialize and restore generator indices (in a CDB).

  - add VCS (aka vacuous lexical entries) slot to simple MRS exchange
    format; this is intended to support generation from MRSs without
    having to invoke trigger rules (e.g. in ACE) and should ordinarily 
    not be visible.

  - experimentally, allow a grammar to invoke a set of transfer rules
    on generator inputs, e.g. to patch MRSs up or increase robustness.

  - experimentally, generalize the top-level (empty) path in feature
    structures when testing subsumption for packing; see `dag.lsp'.

  - new all-records() function in CDB.

  - fix bug in index-for-generator(), viz. setting *top-semantics-type*
    when restoring cached indices, so that predicate underspecification
    works with construction semantics too.

  - bug fixes in transfer code; remove most LOGON-specific settings.

  - bug fixes in LUI and LSP.
  
please note that some of the above remain disabled by default, i.e. are
conditionalized on the :logon feature.  i plan to go through these and
eliminate unnecessary conditionals over the next few days.

regarding [incr tsdb()], there will be more to say, but note that there
are new fields in several relations, i.e. generating new profiles will
require up-to-date skeletons (otherwise, the code will refuse to write 
to old-style profiles).  as always, reading old profiles should remain
functional, all the way back to the 1996 data format.

                                                          best  -  oe

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+++ Universitetet i Oslo (ILN); Boks 1102 Blindern; 0317 Oslo; (+47) 2285 7989
+++     CSLI Stanford; Ventura Hall; Stanford, CA 94305; (+1 650) 723 0515
+++       --- oe at csli.stanford.edu; oe at hf.uio.no; stephan at oepen.net ---
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