持久Reference-Sets

A裁判erence-setis removed from ther-stackand destroyed as soon as its originating mapping rule is deactivated. If there is a need to keep裁判erencesfor a longer period then its裁判erence-setcan be made to persist on the sets that still reside in ther-stack. A裁判erence-setwhose originating mapping rule is being deactivated can be made to persist either at the top or at the bottom of ther-stack.

Thepersistattribute in theelement allows a裁判erence-setto be persisted beyond the deactivation of its originating mapping rule. The valid values for thepersistattribute aretrueandfalse. A裁判erence-setis not persisted by default, so an absentpersistattribute has the same effect as setting it tofalse.

persist=”true|false”>
...

By default, a persistent裁判erence-setpersists in the set at the top of ther-stack. This persistent set will be destroyed as soon as its containing set is also destroyed. For convenience, the xfMap allows a set to be persisted in the set at the bottom of ther-stack. Theelement’s optionalpersist-inattribute can be used to control this. The valid values for thepersist-inattribute are父andbase. Setting thepersist-inattribute tobaseallows a set to be persisted at the bottom of ther-stack. By default, a persistent裁判erence-setwill be persisted in the set at the top of the stack – this is the same as setting thepersist-inattribute to父.

persist-in=”parent|base”>
...

A reference-setpersisting in another裁判erence-setoverwrites the references in the host set.

Persist options may also be set with xfMap expression elements via children elements. The value for the name attribute may be persist or persist-in.

For example:

 ... expression or expression sequence evaluating to “true” or “false” ...   ... expression or expression sequence evaluating to “parent” or “base” ... ...