pt:multi

In a similar fashion to required, the multi property functions slightly differently depending on whether it is declared within a fetch context or not.

When fetching

In this context multi is used to signal whether the pre-processor should expect to find multiple instances of an element in the active source, and optionally how many. An evaluated value of True (as achieved with any boolean XPath expression such as true() or even 1 = 1) will duplicate the template element for each matched instance in the active source. If instead the expression evaluates to an integer, N, the effect is functionally equivalent to if the element (subtree) was repeated N times in the template instead, with the exception that the pre-processor will raise an error if the number of matched source instances is not equal to N.

<geom:Motion_Counter pt:fetch="true()" pt:sources="primary">
    <geom:name/>
    <local_identifier/>
    <geom:Motion_Counter_Index pt:multi="12"> 
        <geom:index_id/>
        <geom:index_value_number/>
    </geom:Motion_Counter_Index>
</geom:Motion_Counter>

Here, setting multi to 12 signals that we expect the pre-processor to find exactly 12 instances of geom:Motion_Counter_Index in the active source label. Specifying the cardinality is not strictly necessary, but in this example we know that the motion counter has exactly 12 indices, which we wish to express to increase the descriptiveness of the template and enable the additional consistency checks.

When not fetching

Outside the fetch context, the multi property can be used for convenience to collapse repeating (identical) elements in the template into a single entry. In this mode the property expression must evaluate to an integer (as a value of True would not be very helpful), which indicates the total number of element instances that will be made available by the pre-processor.