<p:for-each name? = NCName> ((p:iteration-source? & (p:output | p:log)*), subpipeline) </p:for-each>
The <p:for-each> step is a loop implementation under XProc. In this way, documents which are assigned to this step are successively processed within a loop in a subpipeline. The input has to be provided as a sequence by a previous step (it has to contain several documents). Alternatively, the content can also be provided by <p:iteration-source>.
<p:iteration-source select? = XPathExpression> (p:empty | (p:pipe | p:document | p:inline | p:data)+)? </p:iteration-source>
<p:iteration-source> is only available in <p:for-each>. As an attribute a XPath expression can be passed on which addresses desired contents from the initial document (of the input port). Alternatively, contents can also be loaded and created via <p:document>, <p:inline> and <p:data>. Then, the documents read in are gradually processed in the subpipeline.
In the following example the functionality of the <p:for-each> step is demonstrated.
<?xml version="1.0" encoding="UTF-8"?> <p:declare-step xmlns:p="http://www.w3.org/ns/xproc" xmlns:c="http://www.w3.org/ns/xproc-step" version="1.0"> <p:input port="source"> <p:document href="FilmCollection.xml"/> </p:input> <p:output port="result" sequence="true"/> <p:for-each> <p:iteration-source select="//Year"/> <p:output port="result"/> <p:rename match="/Year" new-name="Date"/> </p:for-each> </p:declare-step>
The data to be processed are defined by the <p:iteration-source> step. It determines that any “Year“ elements of the source document read in shall be processed. These are sent consecutively to the <p:rename> step which renames the element as “Date“.