stm:set-xpath-eval

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Attribute
xpath	the target path into the operand document
select	optional an unambiguous xpath into the child document fragment contained by the stm:set-xpath-eval element

The stm:set-xpath-eval operation is used to set the value of elements or attributes to a value obtained from an xpath expression. It does not create or modify document structure it cannot be used to create or rename elements. The value to be set is obtained by evaluating an xpath expression located either as the text value of the stm:-set-xpath-eval element or at the xpath location specified by select xpath location of an enclosed fragment. The evaluated xpath expression has the same context as the target xpath, therefore '.' is target node, '..' the parent etc. Both absolute and relative xpaths can be used.

stm:set-xpath-eval is very good at a=a+1 evaluation and assignments since the value of the target node is available in the xpath expression.

Example

Example1: Set attribute value to the size of the elements text string
This example first creates size attributes on all /a/b/c elements. It next sets each of the size attributes to the length of the text contained by the parents c element. The xpath expresion ../text() is the value of the text in c and the string-length() function gives the number of characters in the text.
<idoc>
  <seq>
    <instr>
      <type>stm</type>
      <operand>doc.xml</operand>
      <operator>
        <stm:group xmlns:stm="http://1060.org/stm">
          <stm:create-path newpath="@size" xpath="/a/b/c" />
          <stm:set-xpath-eval xpath="/a/b[1]/c/@size"> string-length(../text()) </stm:set-xpath-eval>
          <stm:set-xpath-eval xpath="/a/b[2]/c/@size"> string-length(../text()) </stm:set-xpath-eval>
        </stm:group>
      </operator>
      <target>this:response</target>
    </instr>
  </seq>
</idoc>
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Example 2: set-xpath-eval with values from Param

In this example we show param substitution. Any element named <param> within an stm operation element is substituted by the document fragment within the param document at the location given by the <param> xpath attribute. In this case we show how the value substituted from the param is actually into an xpath expression which is then evaluated and the result is placed in the operations xpath target.

In detail, this example does an xpath concatenation to form a string with literals interspersed with values obtained from the param. The targets are the food attributes of /a/b/c

<idoc>
  <seq>
    <instr>
      <type>stm</type>
      <operand>doc.xml</operand>
      <operator>
        <stm:group xmlns:stm="http://1060.org/stm">
          <stm:set-xpath-eval xpath="/a/b[1]/c/@food"> concat('I like ',.,', but I prefer ','
            <stm:param xpath="/i/j[1]/k/text()" />')
          </stm:set-xpath-eval>
          <stm:set-xpath-eval xpath="/a/b[2]/c/@food"> concat('I likes ',.,' and I will eat ','
            <stm:param xpath="/i/j[1]/k/text()" />,',' but I really prefers ','
            <stm:param xpath="/i/j[2]/k/text()" />')
          </stm:set-xpath-eval>
        </stm:group>
      </operator>
      <param>param.xml</param>
      <target>this:response</target>
    </instr>
  </seq>
</idoc>
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