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Re: Link-3: Sets, Singletons, and Determinism

From: Joe English <jenglish@crl.com>
Date: Thu, 22 May 1997 18:42:36 -0700
Message-Id: <199705230142.AA06203@mail.crl.com>
To: W3C SGML Working Group <w3c-sgml-wg@w3.org>

W. Eliot Kimber <eliot@isogen.com> wrote:

> As defined in terms of groves in HyTime, a span addresses the list of nodes
> in the grove from the span start to the span end, inclusive, in left-list
> pre-order traversal.

What precisely is a "left-list pre-order traversal"?
I've seen that term used dozens of times and have always
assumed it to mean the same thing as "preorder traversal",
but this makes me wonder.

For example, consider:

    <nameloc id=THESPAN spanloc=spanloc>
	<nmlist nametype=element>  C2 C3  </>
    <z id=Z>
	<a id=A>
	    <b id=B1>
		<c id=C1>...</c>
		<c id=C2>...</c>		<!-- span start -->
	    <d id=D>...</d>
	    <b id=B2>
		<c id=C3>...</c>		<!-- span end -->
		<c id=C4>...</c>

Does THESPAN include B1?  B2?  In a preorder traversal, B2 is visited
between C2 and C3, but B1 is not.  Does THESPAN include A?  Z?

I can think of three reasonable (to me) interpretations of SPANLOC:
THESPAN consists of either:

    (1) only C2, D, and C3, and their respective content; or
    (2) B1, and B2, in addition to (1) (since the span crosses
	B1's and B2's boundaries); or
    (3) A, in addition to (2) (since A is the root of the smallest
	subtree containing the span).

Going by the "preorder traversal" interpretation, THESPAN
contains (1) and B2, but not B1 or A.  Is this correct?

> The nodes are either those in the content tree that
> includes all of the span or the nodes in the subnode tree that includes the
> span.

That can't be right!  That would mean that THESPAN contains
the Z and A nodes, but *not* C2, C3, or any of their descendants!

--Joe English

Received on Thursday, 22 May 1997 21:45:25 UTC

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