Recently in XPath Category

This was meant to be one big huge milestone. If only it was done 3 years ago. I hope it's not too late though:

XQuery, XSLT 2 and XPath 2 Are W3C Recommendations

2007-01-22: The World Wide Web Consortium has published eight new standards in the XML family for data mining, document transformation, and enterprise computing from Web services to databases. "Over 1,000 comments from developers helped ensure a resilient and implementable set of database technologies," said Jim Melton (Oracle). XSLT transforms documents into different markup or formats. XML Query can perform searches, queries and joins over collections of documents. Using XPath expressions, XSLT 2 and XQuery can operate on XML documents, XML databases, relational databases, search engines and object repositories.

Wow. Congrats to everybody envolved. Lots of reading now.

XslCompiledTransform implements the following useful MSXML extension functions. But what if you need to use them in XPath-only context - when evaluating XPath queries using XPathNavigator?

When working with XPath be it in XSLT or C# or Javascript, apostrophes and quotes in string literals is the most annoying thing that drives people crazy. Classical example is selections like "foo[bar="Tom's BBQ"]. This one actually can be written correctly as source.selectNodes("foo[bar=\"Tom's BBQ\"]"), but what if your string is something crazy as A'B'C"D" ? XPath syntax doesn't allow such value to be used as a string literal altogether- it just can't be surrounded with neither apostrophes nor quotes. How do you eliminate such annoyances? 

The solution is simple: don't build XPath expressions concatenating strings. Use variables as you would do in any other language. Say no to

selectNodes("foo[bar=\"Tom's BBQ\"]") 

selectNodes("foo[bar=$var]")

How do you implement this in .NET? System.Xml.XPath namespace provides all functionality you need in XPathExpression/IXsltContextVariable classes, but using them directly is pretty much cumbersome and too geeky for the majority of developers who just love SelectNodes() method for its simplicity.

The Mvp.Xml project comes to rescue providing XPathCache class:

XPathCache.SelectSingleNode("//foo[bar=$var]",
    doc, new XPathVariable("var", "A'B'C\"D\""))

And this is not only stunningly simple, but safe - remember XPath injection attacks?

You can download latest Mvp.Xml v2.0 drop at our new project homepage at the Codeplex.

I still own xsl.info and xpath.info domain names and still have no time to build anything around there. If anybody have any ideas about any community driven projects - let me know, I'm willing to donate domain name and may be participate.

And if anybody want to buy these domain names - I'm willing to sell.

Dimitre Novatchev has uploaded another FXSL 2.0 release. FXSL is the best ever XSLT library:

The FXSL functional programming library for XSLT provides XSLT programmers with a powerful reusable set of functions and a way to implement higher-order functions and use functions as first class objects in XSLT .

Now XPath 2.0 functions, operators and constructors as well as XSLT 2.0 functions have "higher-order FXSL wrappers that makes possible to use them as higher order functions and to create partial applications from them".

To fully understand the value of this stuff take a look at Dimitre's article "Higher-Order Functional Programming with XSLT 2.0 and FXSL".

Just in case if somebody have missed this cool new tool - check out DonXML's into into XPathmania. It's free open-source Visual Studio add-in for XPath development. I just can't live without it already. Very cool stuff, part of our Mvp.Xml project.

W3C has released fresh versions of the Candidate Recommendations of XML Query 1.0, XSLT 2.0, XPath 2.0 and supporting documents. No big deal changes - xdt:* types has been moved to xs:* namespace (damn XML Schema). See new XQuery1/XPath2 type system below. Looks like XSLT2/XPath2/XQuery1 are moving fast toward Proposed Recommendation. What's weird is that new documents all say "This specification will remain a Candidate Recommendation until at least 28 February 2006." Must be a mistake. Anyway, what are now chances for XSLT 2.0 in the .NET? Next major .NET release (Orcas) is expected October 2007 or so (forget newly announced .NET 3.0, which is actually .NET 2.0 + Avalon + Indigo). Plenty of time for XSLT2 to reach Recommendation status, even provided that Microsoft actually freezes codebase 6 months before shipping.

That's a big milestone in a 6-years-going-so-far design-by-committee experiment: XSLT 2.0, XQuery 1.0 and XPath 2.0 are finally W3C Candidate Recommendations. That means that W3C now officially calls for implementations (which shows another weirdness of the design-by-committee process as XQuery alone has about 40 implementations already as per Ken North). CR phase will last at least till 28 February 2006, that means late 2006 is probably the timeframe for the XSLT 2.0, XQuery 1.0 and XPath 2.0 Recommendations.

XPathReader v1.1 is available for download.

XPathReader is originally developed inside Microsoft and then dropped out as open-source implementation of a pull-based XML parser that supports XPath queries while parsing the XML document. It's basically XmlReader that supports streaming subset of XPath 1.0. Read "The Best of Both Worlds: Combining XPath with the XmlReader" article for more info about XPathReader.

New in this release:

• Support for look-ahead in predicates such as "foo[bar='baz']". This is done via internal caching using XmlBookmarkReader. This behaviour can be turned off using XPathReader.LookAheadInPredicates property.
• XPathReader.dll is now has a strong name, so it can be called from strongly named assemblies
• AllowPartiallyTrustedCallers attribute is applied, so XPathReader.dll can be called by partially trusted callers (e.g. in ASP.NET)
• A nasty bug with != in predicates is fixed

In .NET 2.0 XPathNavigator finally has SelectSingleNode() method! MSXML and XmlDocument (XmlNode actually) have it forever and it's so widely used because it's soooo handy. Obviously despite its name, XPathNavigator.SelectSingleNode() returns not a node, but node equivalent in XPathNavigator's data model - XPathNavigator. And this method is even better than XmlNode's one, because it has overloads accepting compiled XPathExpression, so when running within a loop you don't have to pay XPath compilation price on each iteration. That's another reason to switch completely to XPathNavigator API when processing XML in .NET 2.0.