xml query language xsl defines a u201c pattern u201d syntax which identifies nodes within an xml document this capability provides the equivalent of an sql where clause xsl is further discussed in professional xsl by kurt cagle michael corning et al wrox press inc 2001 isbn 186 100 3579 the xml data buffer tags shown without any data entered associated with the image elements or controls 4 5 6 and 7 appearing in form 3 would appear as follows in the preceding example the data item identifier patient address zipcode resolves to a data item having one object property the value of the zip code the data item identifier patient address resolves to a data item that is an entire object containing several objects with their own properties multiple lines of address information plus city state and zipcode and the data expression patient address state pa for example resolves to a data element which is an array composed of a repeating group of objects i e those patients who live in pennsylvania thus a data item identifier resolves to a data item or to some portion of data within the embedded xml document containing external data in xml this reference is to a document node that is one branch of the xml document as illustrated for example in fig1 a data item identifier can represent the data source for a prompt element the data target destination for a prompt element or both for example a combo box needs a data item.