Event mapping is a PeopleSoft delivered framework which helps applications and customers adapt PeopleSoft for business needs with minimum upgrade impact. Benefits include extension and modification of PeopleSoft for specific business needs, the introduction of Business Logic as configuration instead of customization, the developing of a re-usable code and artifacts, and customer code not being overwritten by PS delivered code during an upgrade.
The architecture of event mapping in PeopleSoft can be viewed in layers, the first being the PeopleSoft database. Within this database is the PeopleSoft Application Server. This is where event mapping is introduced. It is divided into two different boxes, PeopleSoft Entities and PeopleSoft Events. The interaction between these PeopleSoft Entities and Events can be classified into three categories; Model, Controller, and View. Model represents all update PeopleSoft fields and data entities, extend data, and customization. The Control layer is where adding/updating business logic gets executed. Then the View layer is the rendering layer, where you can change and/or hide labels.
For more information about event mapping, check out this video presented by Ramasimha Rangaraju, Director, PeopleTools and Anusha Srivatsan, Development Manager, PeopleTools: PeopleSoft Event Mapping Framework.