Altova Mailing List Archives


Re: RFC: thoughts for a "streamlined" XML syntax variant...

From: BGB <cr88192@-------.--->
To: NULL
Date: 5/14/2012 9:25:00 PM
On 5/14/2012 4:49 AM, Manuel Collado wrote:
> El 11/05/2012 19:40, BGB escribió:
>> ...
>> example, say that a person has an expression like:
>> <if>
>> <cond>
>> <binary op="&lt;">
>> <ref name="x"/>
>> <number value="3"/>
>> </binary>
>> </cond>
>> <then>
>> <funcall name="foo">
>> <args/>
>> </funcall>
>> </then>
>> </if>
>>
>> representing, say, the AST of the statement "if(x>3)foo();".
>>
>> the parser and printer could use a more compact encoding, say:
>> <if
>> <cond <binary op="&lt;" <ref name="x"/> <number value="3"/>>>>
>> <then <funcall name="foo" <args/>>>
>> >
>
> In that case the slashes in the "/>" endmarks are probably superfluous.
>

in depends on how the parser works.

given the intention that the new syntax be a direct extension of the 
existing syntax, rather than entirely replacing it, the '/' is still 
needed in order to avoid the syntax becoming ambiguous (how do you 
otherwise distinguish between an empty tag and the start of a list which 
is terminated by a closing tag?...).

there are potentially more complex ways to deal with it, such as 
determining the type of the next matching closing tag, but this is 
problematic and potentially costly.

example:
<a><b><c>...</c></a>
a begins, scans forwards, sees matched closing a.
b begins, scans forwards, sees that next closing tag is a, concludes it 
does not contain c, ...

the problem here is that in the naive case, this could cause the parser 
to require around O(n^2) time, rather than O(n) time, so it is better to 
avoid ambiguity.


or such...

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