You are reading O'Reilly XForms Essentials by Micah Dubinko. (What is this?) - Buy XForms Essentials Online

constraint
Prev Model Item Properties Next

Name

constraint

Synopsis

Allowed values:any XPath expression; the result is interpreted as a boolean.
Default value:true

This property imposes an additional XPath-based constraint on the validity of the attached node.

If the XPath expression with this property evaluates to false, the attached node is guaranteed to be invalid. If it evaluates to true, however, it's still possible (through XML Schema constraints) that the attached node might be invalid.

minOccurs and maxOccurs

Earlier drafts of the XForms Specification included model item properties for minOccurs and maxOccurs, designed to restrict the number of times a repeated node could occur. Difficulties arose in describing how these would actually work, since any given sequence of repeating nodes could have differing restrictions on each node.

Such restrictions can still be done with the calculate property, as shown in this example, which restricts the number of item children to more than zero and less than ten: 

<xforms:bind nodeset="items" constraint="count(item) &gt; 0 and count(item) &lt; 10"/>
Prev Up Next
calculate Home p3ptype