Production Template Directive
The *Production template directive specifies valid combinations of members that can appear within a particular construct. This directive can appear only within templates with *Type: CONSTRUCT.
If this directive is present, the production is evaluated against each instance of a construct that is bound to the production's host template. The host template is the template that contains the Production directive. If the Production directive evaluates to FALSE, a warning message is issued, but processing is otherwise unaffected. If the host template contains no Production directives, no validation is performed.
The *Production directive appears at the root level of the host template construct. If more than one *Production directive appears at the root level, only the most recently defined directive will be evaluated. The result of evaluating a Production directive is a Boolean value.
The *Production directive is itself a construct. The child elements of the *Production directive are either other *Production constructs or *Member constructs or a combination of both (also called child productions). You cannot use namespace directives within the *Production directive.
Each child production that is contained within the *Production directive also evaluates to TRUE or FALSE. The Production directive is evaluated by first evaluating each of its child productions. The result for the enclosing parent Production directive is obtained by performing a simple logical operation on the results of each of the child productions. The type of logical operation to apply is specified by vValue of the *Production directive.
The value of the *Production directive can be one of the following symbols: EXACTLY_ONE, SATISFY_ALL, or AT_LEAST_ONE.
The following example shows a production directive.
*Production: EXACTLY_ONE
{ ... child Productions ... }
The following algorithm defines the production directive values:
If the production specifies EXACTLY_ONE, this production evaluates to TRUE if exactly one child production evaluates to TRUE, with the remainder being FALSE. Otherwise, the production evaluates to FALSE.
If the production specifies SATISFY_ALL, this production evaluates to TRUE only if all of the child productions evaluate to TRUE. Otherwise, the production evaluates to FALSE.
If the production specifies AT_LEAST_ONE, this production evaluates to TRUE if at least one or more child productions evaluate to TRUE. Otherwise, the production evaluates to FALSE.
*Production directives can be nested to arbitrary depth.