Possibly the most powerful and useful new feature added to the CallXML3.0 markup is the ability to perform application operations with XPath. Never heard of XPath? Then you are in the right place to learn, my friend. While a full dissertation of the uses of XPath is somewhat outside of the scope of this document, we will cover the basics of XPath, and detail in full how you can use XPath within your CallXML 3.0 applications. For the uninitiated, an XPath expression specifies a specific pattern that selects a set of XML nodes, and XSLT templates then use these patterns when applying transformations. In other words, XPath is a language for navigating through element nodes of a specific XML document,(or even a txt document!), and importing the returned information into the existing application context. Voxeo uses the XPath version 1.0 syntax, and a few Voxeo-specific function extensions to allow the developer even more options.
XPath Expressions: Part 1 - Luckily for you, XPath has a relatively simple method for plucking out specific nodes of an XML document to retrieve information from. All we need to do is to take a close look at the XML document in question, and make sure our element and node names match up with the 'addressing' syntax. This subsection illustrates the basic 'Axes' commands that you can employ to pull specific data from an XML, (or even text-based!) source.
Xpath Expressions: Part 2 - Building on what we have learned in the first section of our Xpath documentation, we now delve into the usage of Xpath predicates, which help us to filter results based on user criteria. Also covered in detail is the usage of the available Operators that we can use to further manipulate our data. We also include numerous code examples that help you get a grasp of how you can use these features in your own CallXMl3.0 applications.
Xpath Functions - Like any good markup, Xpath comes packaged with a number of built-in functions that we can use to further modify our data that is returned from a query. This section of the Xpath documentation lists and defines these various functions in an easy-to-understand manner, and further explores function usage with code examples that show how they can be used in a real-world application
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