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RE: Streaming Transformations for XML

• To: "Petr Cimprich" <petr@g...>,<xml-dev@l...>
• Subject: RE: Streaming Transformations for XML
• From: "Leigh Dodds" <ldodds@i...>
• Date: Wed, 13 Feb 2002 14:53:48 -0000
• Importance: Normal
• In-reply-to: <3C6A6D75.80304@g...>

Interesting. Looks to like XSLT-- or AFs++. I think this 
is worth pursuing further.

Lately, I've realised that while we've got a nice collection of 
schema languages, there's not a great deal to choose from in 
other areas (except tree models perhaps). So exploring other 
kinds of transformation mechanisms seems like a good thing 
to me.

I can see this being particularly useful when written as 
a Cocoon Transformer.

L.

> -----Original Message-----
> From: Petr Cimprich [mailto:petr@g...]
> Sent: 13 February 2002 13:43
> To: 'xml-dev@l...'
> Subject:  Streaming Transformations for XML
> 
> 
> I'm playing with an idea of a streaming transformation language. I don't 
> mean things like forward-only streamable subsets of XSLT or building 
> subtrees on request only, but an alternative language designed for 
> streaming transformations. From a bit different point of view, it would 
> be a language to define SAX filters.
> 
> Such a hypothetic languge (let me call it STX) could use an XML, 
> XSLT-like syntax with templates. However, the meaning of templates would 
> be quite different from this of XSLT. Matching expressions could 
> consists of SAX-related axes and simple, XPath-like identifier, for example.
> 
> STX transformations will be, of course, much less powerful than XSLT; it 
> will be as powerful as a SAX filter can be. On the other hand, the new 
> language could provide an memory inexpensive way to handle simplier 
> transformation.
> 
> Instead of a BNF definition, I append an example processed by 
> non-existing STX processor. It should provide you with some very basic 
> feeling about a possible syntax and semantics of the language.
> 
> I wonder whether the benefits of having simple streaming transformations 
> worth to learn a new language (and to implement a processor). Also, I 
> haven't been able to find a similar solution or idea on the Net, but I 
> expect there must a similar effort in the huge XML community. So, any 
> pointers are welcome to prevent me from reinventing the wheel.
> 
> Regards,
> Petr
> 
> --------------
> 
> * Example
> 
> ** Transformation:
> 
> <stx:transform xmlns:stx="some_namespace_here">
> 
>   <stx:variable name="date" select="'Monday'"/>
> 
>   <stx:template match="element-start::list">
>     <stx:copy-of attributes="all">
>       <stx:attribute name="date" select="$date"/>
>     </stx:copy-of>
>   </stx:template>
> 
>   <stx:template match="element-end::list">
>     <stx:copy-of/>
>   </stx:template>
> 
>   <stx:template match="element-start::item">
>     <stx:copy-of/>
>     <id><stx:value-of select="@id"/></id>
>     <stx:if test="@id=2">
>       <note>the item we have been looking for</note>
>     </stx:if>
>   </stx:template>
> 
>   <stx:template match="element-end::item">
>     <date><stx:value-of select="$date"/></date>
>     <stx:copy-of/>
>   </stx:template>
> 
>   <stx:template match="character::*">
>     <text><stx:copy-of/></text>
>   </stx:template>
> 
> </stx:transform>
> 
> ** Input data:
> 
> <list id="19">
>   <item id="1">A</item>
>   <item id="2">B</item>
>   <item id="3">C</item>
> </list>
> 
> ** Output:
> 
> <list id="19" date="Monday">
>   <item>
>     <id>1</id>
>     <text>A</text>
>     <date>Monday</date>
>   </item>
>   <item>
>     <id>2</id>
>     <note>the item we have been looking for</note>	
>     <text>B</text>
>     <date>Monday</date>
>   </item>
>   <item>
>     <id>3</id>
>     <text>C</text>
>     <date>Monday</date>
>   </item>
> </list>
> 
> -- 
> Petr Cimprich
> Ginger Alliance
> www.gingerall.com
> 
> 
> 
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