Re: Possible use of <INSERT> - serious inquiry

Murray Altheim (murray@spyglass.com)
Tue, 19 Mar 1996 10:27:50 -0400


Message-Id: <v02110100ad746c91d155@[140.186.34.50]>
Date: Tue, 19 Mar 1996 10:27:50 -0400
To: MegaZone <megazone@livingston.com>
From: murray@spyglass.com (Murray Altheim)
Subject: Re: Possible use of <INSERT> - serious inquiry
Cc: www-html@w3.org

>I just spent a while stufying the <INSERT> tag proposal at
><http://www.w3.org/pub/WWW/TR/WD-insert.html>
>
>This seems to me to be perfectlyu extensible for the inclusion of
>other text files, as we have recently discussed.
>
>Now, my serious question is, at this time could one simply use
>
><insert
>        data="http://www.mysite.com/path/file.html"
></insert>
>
>I don't *think* so from my reading, but I'm looking for other input.

A valid HTML document is of the form:

    <!DOCTYPE ...>
    <HTML>
    <TITLE>...</TITLE>
    <BODY>
    ...
    </BODY>
    </HTML>

To insert another valid HTML document anywhere in this structure
invalidates the document, unless the inserted entity is a document fragment
and it is allowed at the inserted location. I don't think I've ever seen
any proposed resolution to this problem, where in practice folks will
probably simply insert complete HTML documents. It would be a royal mess,
as it puts a heavy requirement on authors to do their own entity
management, something I've seldom seen in practice.

Also, the issue of whether or not the inserted document exists on the same
system may or may not be a problem, depending on your SGML system. While a
validating parser may be able to locate external entities via URL, this is
not a requirement in SGML (ISO 8879:1986), it is simply a nice feature of
nsgmls. Dan Connolly and I have gone 'round on this one before.

So strictly speaking (following HTML as an SGML application, according to
both 8879 and RFC 1866 as current specifications) I don't believe we can
*require* an SGML system to understand URLs in order to parse a document.
Therefore, any feature that required an insertion of content based upon
URLs may not be conformant. Someone may correct me on this, but this is the
way I read 8879.

Murray

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     Murray Altheim, Program Manager
     Spyglass, Inc., Cambridge, Massachusetts
     email: <mailto:murray@spyglass.com>
     http:  <http://www.stonehand.com/murray/murray.htm>