In addition, as XSLT becomes more pervasive--particularly in the Web services arena--the speed at which an engine can perform transformations is critical. Hardware-based XSLT engines, such as DataPower's XA35, are crucial to the success of your XML-based projects. But to take advantage of such products, an editor must be able to use an alternative external XSLT engine.
Full Debugger
An XSL transformation may include data manipulation, such as mathematical calculations, iterations over sequences of elements and even the restructuring of data elements within the original XML document. These processes are no different than those used with C or Java code, so it's imperative that your XSLT editor include a full debugger. When things go wrong, you'll want to be able to walk through the transformation. Though "print" statements littered throughout your code is one method of debugging, it's not efficient. A full debugger with step capabilities, break points and watch points makes the debugging process immeasurably easier.
A large portion of XSLT consists of finding specific elements within an XML document, then performing some sort of manipulation on the element or subelements. To search efficiently through an XML document, which can be large, many editors use XPath.
XPath queries can be complicated and may involve the use of specific functions, such as local-name() and position(). Although XSL provides some mechanisms for manipulating elements, it is rare to find XSLT without XPath, which provides the basic syntactical constructs necessary to select and address nested elements.
A good XSLT editor should support XPath queries and help you evaluate them. XPath analysis can speed up the construction of XSLT by letting you test XPath queries to see the resulting node. Such analysis removes the need to run the transformation in order to determine whether your XPath query is correct.
Tag Handling
No development environment would be complete without color syntax highlighting. Even the most rudimentary editor should provide customizable highlighting and support not only XSLT but XSL, XML and HTML.
XSLT editors' tag handling capabilities have grown considerably and are now almost on a par with a professional C/C++/Java environment. Features such as drop-down lists make writing XSLT a breeze. The "automatic but optional feature" lists attributes with mandatory values and can reduce mistakes and save you time.
Miscellaneous Goodies
Version-control integration really should be a requirement. Project-based management of files--keeping your XSL, XSLT and other related files together--is another. Finally, a hierarchical, tree-based view of your XML is a great option, especially if provided internally rather than through an external browser.
Lori MacVittie is a Network Computing technology editor working in our Green Bay, Wis., labs. Write to her at lmacvittie@nwc.com.
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