BUILDING XSLT APPLICATIONS in Font

Making PDF 417 in Font BUILDING XSLT APPLICATIONS

Figure 12-9. Viewing TVGuide6.html in Internet Explorer The flags on Ally McBeal and Taboo are being generated based on data held in flags.xml. If you wanted to add different kinds of flags, or change the location of the flags that the document is using, then you could edit flags.xml without touching the stylesheet.

One of the main ways in which you can use external documents to augment your stylesheet is to provide lookup tables. Lookup tables encode the mapping between an identifier and a piece of information, as in flags.xml. They are used to do things like the following: Give translations for a term in different languages. Provide the labels used for different codes. Hold the mapping between abbreviations and full names. Specify the ordering of a set of strings (the position of the node acts as its identifier). Often the set of mappings held in the XML lookup table will be quite large, or you will want to access it many times. As you learned in 10, the quickest way of accessing information by the value of one of its attributes or descendants is using a key, defined with an <xsl:key> element and accessed using the key() function. However, the key() function (and the id() and idref() functions) usually only searches for the relevant element within the document that holds the context node. As we ve seen, the

lookup tables are often held in external documents. If you try to use the key while processing an element in the source document, then the XSLT processor will only look in the source document for the elements that match the key. There are two ways to use a key on an external document. The first is to use the optional third argument of the key() function, specifying a node in the external document. If you use the document node of the external document, then the entire document will be searched; otherwise you ll just search the descendants of the node you specify. For example: key('keyName', keyValue, doc('externalDocument.xml')) Alternatively, you can change the context node from the source document to the document in which the lookup table is located. The easiest way to do this is to use the key() function in a step within a path whose earlier steps access the external document. For example: doc('externalDocument.xml')/key('keyName', keyValue) This second option is easiest to use if you have several external documents to search. But remember that the expression you use to select the key value will be evaluated relative to the node(s) selected by the previous step. If the key value comes from the original document, you should store it in a variable so that you can get hold of the value easily.

change the context node to a node in the external document and then use the key(), id(), or idref() functions as normal.

The data in TVGuide.xml is made up of two main sections: the channels and their program listings, and information about series. In the original plan for the XML TV guide, back in 1, we wanted the information about series to be held in a separate document from the program listing. In this example, we ll separate out this series information into another file, series.xml, and access information from that file using keys. Our first task is to separate the information from TVGuide.xml into two documents: TVGuide2.xml for the program listing and series.xml for the series information. TVGuide2.xml looks like this: < xml version="1.0" encoding="ISO-8859-1" > <TVGuide> <Channel>...</Channel> <Channel>...</Channel> ... more <Channel> elements ... </TVGuide> while series.xml looks like this: < xml version="1.0" encoding="ISO-8859-1" > <SeriesList>