!!! Overview
[{$pagename}] or ([MP]) is applied to <add> events and serves to automatically link an object in the Identity Vault with the corresponding object in the application. The [Subscriber Channel] and [Publisher Channel] usually have different Matching Polices. 

The [{$pagename}] is usually implemented using the DirXML Script action <do-find-matching-object>.
The [{$pagename}] is executed after the Event Transformation Policy and before the Create Policy.

Matching policies, are within the [Subscriber Flow] the [{$pagename}] uses the [Policy Set Interval Values] of 6, and [Publisher Flow], the [{$pagename}] uses the [Policy Set Interval Values] of 7, and look for an object in the [Application namespace] data store that corresponds to an un-associated object in the source datastore.
 
It is important to realize that Matching policies are not always needed or desired.

For example, a [{$pagename}] might not be desired when performing an initial migration if there are no preexisting or corresponding objects.

A [{$pagename}] must be carefully crafted to ensure that the [{$pagename}] does not find false matches.

!! More Information
There might be more information for this subject on one of the following:
[{ReferringPagesPlugin before='*' after='\n' }]