For example, a message might contain a 'count' element
whose value gives the number of occurrences of a later element that
is an array. The array element uses an expression in the Occurs Count
property, which refers to the 'count' element.
The DFDL expression
language is a subset of XPath 2.0. Expressions follow XPath 2.0 syntax
rules, but are always enclosed in braces '{' and '}'.
The properties
that support DFDL expressions include:
- assert (the test property of the assert takes the expression)
- binary float rep
- byte order
- discriminator (the test property of the discriminator takes the
expression)
- encoding
- escape character
- escape escape character
- initiator
- input value calc
- length
- occurs count
- output new line
- output value calc
- separator
- terminator
- text boolean false rep
- text boolean true rep
- text standard decimal separator
- text standard exponent character
- text standard grouping separator
You can use the XPath Expression Builder to build the expression.
Either use content-assist on the property value, or click the property
wizard button beside the property in the properties area.