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From Erik Hatcher <e...@ehatchersolutions.com>
Subject Re: "Advanced" query language
Date Tue, 06 Dec 2005 09:50:02 GMT

On Dec 5, 2005, at 9:07 PM, Yonik Seeley wrote:
> There is one little problem with XML though...  It's inability to
> directly represent binary data, or even all unicode code points (no,
> entities don't fix this).  I use binary data in lucene to represent
> some numerics, and that can't be represented in standard XML.  An
> application specific escaping mechanism can be used, but then you are
> a step away from standard XML.
>
> example:  <tag>&#0;</tag> is not valid XML
>
> If we go with XML, I think this must be solved (or else we are at the
> point where we can only represent a subset of queries that lucene can
> handle again).

Can you give an example of a query that needs binary information?   
Also I'd be curious to see a problem with Unicode code points in XML,  
if you have one handy.

Even something like setBoost(float f) isn't taking a String.  But the  
XML->Query mapping would translate <Query boost="2.0"> by parsing the  
boost attribute and calling setBoost appropriately.  Is this what you  
mean?

For example, Ant has this sort of type mapping capability built-in.    
Here's some info on how that works:

	http://ant.apache.org/manual/develop.html#writingowntask  
("Conversions Ant will perform for attributes" section)

I described this in some more detail in a JavaPro article a couple of  
years ago also:

	http://www.fawcette.com/javapro/2003_02/magazine/features/ehatcher/  
(must register to see the full article, unfortunately)

I'm confident that XML can accommodate our needs just fine, and any  
other text transmission would have to re-solve many issues that XML  
has already solved.

	Erik


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