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From "Jeffrey Rodriguez" <jeffreyr...@hotmail.com>
Subject Re: Way to link schema to parser instead of particular document instance?
Date Tue, 12 Sep 2000 08:26:45 GMT

Hi Travers,
The answer is no in the current version of Xerces, but it is in the
list of feature to add to Xerces and in the design of Xerces2.
This feature is also known as Grammar caching. This is very useful
in Server environments. e.g. an SVG server.

Grammar caching could be implemented as a combination of properties
and features.
A feature could be implemented such that it indicates the default
cache grammar ( dtd or schema) and a property sets the caching behavior for 
the parser. The default would be to false so we don't cache a server
program could set the caching behavior to true so the default cache grammar 
is used instead.
The cache grammar will be loaded once and reused multiple times
until the parser caching behavior is reset to false.


Hope this helps,

             Jeffrey Rodriguez
             IBM Silicon Valley
             XML Development


>From: "Travers Waker" <traversw@innoforge.co.za>
>Reply-To: general@xml.apache.org
>To: <general@xml.apache.org>
>Subject: Way to link schema to parser instead of particular document 
>instance?
>Date: Tue, 12 Sep 2000 09:53:40 +0200
>
>Hi.
>
>I'm wondering if there is a way to make Xerces validate using a particular
>schema regardless of what XML document is being parsed.  The way I get it 
>to
>validate using a schema now is to set the schemaLocation to a file
>containing the schema in the XML document itself.
>
>This seems quite inefficient if you're validating many XML documents with
>the same schema.  Every time a new document is parsed, the schemaLocation
>has to be read, the schema file (*.xsd) has to be loaded, the parser has to
>set itself up for validation with this scahem and only then can parsing and
>validation take place.
>
>What I would prefer to do is to tell the parser to always validate using a
>particular schema.  This would eliminate the time wasted by reloading the
>schema file every time.  This is important to me because the application 
>I'm
>writing is a server that accepts XML formatted request messages from
>clients.  The schema used is the same every time.  It would be nice to
>initialize the parser to always use the same schema because:
>
>1.  Less time wasted (as mentioned already).
>2.  One doesn't want the incoming XML message dictating what schema is used
>to validate it - If and incorrectly formatted message makes its way into 
>the
>server it will cause problems (eg null pointer exceptions because you are
>assuming data is present when it is not).  Because of this, the server
>itself must decide what schema to apply to the incoming XML message.  The
>only way I can think of doing this is to prepend the lines specifying the
>schemaLocation to each XML message as it arrives at the server, before it 
>is
>parsed.  To me, this seems more like a "quick and dirty" workaround than 
>the
>proper way to achieve what I am trying to do.
>
>Has anyone got comments or suggestions?
>
>Thanks for any responses.
>
>Travers Waker
>
>
>
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