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POSteps and involvement of implementing a parser (in .Net - and in this case XPath 2.0)
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  1. POSteps and involvement of implementing a parser (in .Net - and in this case XPath 2.0)
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    copied!<p>In the lack of any good free XPath 2.0 implementations for .Net build upon Linq to XML I have thought about implementing my own (also for the experience). But just to be clear (and not building something that exists) these are the XPath 2.0 implementations I have found:</p> <ul> <li>Saxon .Net</li> <li><a href="http://qm.codeplex.com/" rel="nofollow noreferrer">Query Machine</a> - I had problems with this - exceptions with the examples</li> <li><a href="http://xqsharp.com/xqsharp/" rel="nofollow noreferrer">XQSharp</a> - may be good, but is commercial (single developer ~300 $)</li> </ul> <p>Now, I want some thoughts on how difficult it is to implementing some language such as XPath 2.0 expressions. I have found this link which have a EBNF for XPath 2.0 expression: <a href="http://www.w3.org/TR/2007/REC-xpath20-20070123/#id-grammar" rel="nofollow noreferrer">http://www.w3.org/TR/2007/REC-xpath20-20070123/#id-grammar</a> and I'm thinking of making it in F# with the fslex/fsyacc combination.</p> <p><strong>My background</strong> (subjective): I have played with these tools before, but only for some simple expressions and a very simple programming language. Furthermore, I have read most of the Dragon book and Appel´s Modern compiler implementation in ML - but unfortunately, I have not put the theory in practice while reading. I've studied computer science in a year now where I have completed courses with theory about ex <code>finite automaton</code>, <code>CFL</code> and algorithms but I have been a developer for years before university (a few years with professional jobs - back-end of websites mainly).</p> <p>Now, the steps of parsing and what I tend to cover:</p> <ol> <li>Lex - Parsing - Reductions: FsLex/FsYacc. I will properly not cover ALL of Xpath 2.0 at first but at least all of what XPath 1.0 can do + a little more.</li> <li>Sematic analysis - I'm not sure about how much there is to this</li> <li>Optimization - I do not tend to cover this (at least not at first)</li> <li>Actual traversing etc.</li> <li>...?</li> </ol> <p>Now, the <strong>concrete questions</strong> in addition to the above:</p> <ol> <li>How difficult is it to make a parser of this size? based on my background, would I could to it?</li> <li>Is there any crucial steps I have missed in regards to XPath 2.0 in particular?</li> <li>Is there any technology I have missed; Do I have to cover more than just XPath 2.0 and <code>XDocument</code> etc. to be able to make the parser?</li> </ol> <p><strong>To be clear:</strong> I want to make a XPath 2.0 expression parser and traverse <code>XDocument</code> etc. with this parsed expression. Which I guess combined is a query engine.</p> <p><strong>Update:</strong> I found this: <a href="http://www.w3.org/2007/01/applets/xpathApplet.html" rel="nofollow noreferrer">http://www.w3.org/2007/01/applets/xpathApplet.html</a> which contains code to parsing and traversing. I think it would be a nice start or reference :-)</p> <p>Your answers will be appreciated.</p>
 

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