[Laszlo-dev] full featured server-side xpath implementation

Mike Santy msanty at mac.com
Fri Mar 25 15:00:54 PST 2005

In evaluating Laszlo by developing a simple application, I have been 
very frustrated with Laszlo's limited XPath support.  Without the 
ability to evaluate nested predicates and  compound expressions, I find 
myself writing quite a bit of code that I could avoid if the XPath 
implementation was more robust.  I've seen recommendations on the lists 
for incorporating more feature-complete ECMAScript or ActionScript 
XPath evaluators into xpath.  While those might be great simple to 
moderately complex queries, they do not seem to have the features that 
Apache's Xalan-J processor supports.  I realize that it wouldn't be 
feasible (or possible) to use Xalan-J in a Laszlo application on the 
client-side, so I started thinking that Xalan-J could be used on the 
server-side to support arbitrary XPath queries.  A servlet/JSP could be 
created that took the XML structure and XPath expression as HTTP POST 
data, and returned the resulting text or XML structure.  This would 
involve more latency for each XPath expression evaluation, but I think 
that the added capabilities would warrant this cost in many situations. 
  As an additional idea, maybe we could programatically specify this 
behavior when complex evaluations must be performed, but default to the 
current client-side mechanism.

I'm looking for feedback on:
1) any more elegant methods for accomplishing full XPath 1.0 compliance
2) where to modify the existing Laszlo codebase to communicate back to 
a server as described above.

Let me know what you think.


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