To create a presentation layer from existing applications about application-to-application integration, document the high-level business process model of the complete system and map from that to the current IT applications. From this information, you can identify necessary shared data and the integration dependencies (real-time and deferred) between the applications.
The second step is to decide on the business priorities for change. Most changes will be in the area of data consolidation and the addition of a new presentation layer. Having focused on a particular application, you need to do a more detailed business process model and pick out the difference between the core process activities and one or more presentation layer refinements. From this information, you can explore various strategies for changing the code.
Wrapping and gateways are effective technologies for interfacing new technology with old mainframe applications. The presentation logic, security logic, and session-control logic in these programs have to be removed, typically by creating new transaction types from the old code rather than changing existing transaction type code.
There are a large number of integration software vendors whose products sometimes have a tactical use. XML will make many of these products irrelevant, but workflow-management products must provide a good source of implementing tracking objects where the business process extends many applications.
Integration servers are useful when the presentation layer accesses many back-end transaction servers, particularly if the transaction server belongs to different companies.