W3C home > Mailing lists > Public > w3c-sgml-wg@w3.org > December 1996

Re: clink/ilink direction (Was: anchor awareness)

From: James Clark <jjc@jclark.com>
Date: Sun, 29 Dec 1996 12:16:52 +0700
Message-Id: <2.2.32.19961229051652.00883290@jclark.com>
To: dgd@cs.bu.edu (David G. Durand)
Cc: w3c-sgml-wg@www10.w3.org
At 16:02 28/12/96 -0500, David G. Durand wrote:
>At 4:11 PM 12/27/96, W. Eliot Kimber wrote:
>>At 05:04 PM 12/27/96 -0500, David G. Durand wrote:
>>>    A "grove" is just a new name for what everyone else in the world calls
>>>a "parse tree".
>>
>>Not exactly correct: groves are a new name for what everyone else in the
>>world calls a direct graph data structure.  It happens that one obvious
>>application of directed graphs is the representation of parse trees, but
>>that's not the only thing groves are used for.  Groves are useful because
>>the provide the following features on top of the basic directed graph of
>>nodes concept:
>
>trees are directed graphs. Are you saying that groves can include cyles of
>nodes (ie node that are their own ancestors), or multiple inheritance
>(directed _acyclic graphs_)? If not, groves are part of that subset of
>directed graphs known as trees, and you are spreading more smoke into the
>air, instead of shedding light on the issues.

Groves are directed graphs (not acyclic), but they can also be considered as
trees.  More precisely:

- A subset of the edges are distinguished as representing
"origin-to-subnode" relationships.  If you delete all edges other than
these, then the graph becomes a single tree.

- A subset of the "origin-to-subnode" edges are distinguished as
representing parent-child relationships.  If you delete all edges other than
these, then the graph becomes a set of disjoint trees: one of these trees is
the normal ESIS-like element structure tree; each attribute assignment (name
plus value) is also its own tree.

James
Received on Sunday, 29 December 1996 00:21:36 EST

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