Pathmaker Programming Guide

Before You Begin
Pathmaker Application Development Overview
3–6 067868 Tandem Computers Incorporated
Top-Down
With the top-down approach, you use the Pathmaker product to create the requesters
for the application first, generally from the highest to the lowest level. Then you create
the services for the application.
You cannot generate and compile a requester that calls a lower level requester that
does not yet exist in the Pathmaker catalog, unless no reference is made to the lower
level requester. If you create a requester that invokes a service that does not yet exist,
you will be able to generate, compile, and test that requester. (During testing, when
any function key that is associated with a nonexistent or incomplete service is pressed,
a message will be sent to the end user indicating that the service is not yet available.)
After all of the services and requesters have been built, the messages between services
and requesters and the parameters between requesters, if any, must be specified.
For services, you must specify the IPC message components for each service and for
each requester that uses those services. For requesters passing parameters, you must
add CALLs in the requester definition and specify which parameters are to be passed.
For requesters receiving parameters, you must specify which parameters are expected.
Finally, the requesters and servers are generated and compiled beginning with the
services and progressing up through the hierarchy of requesters.
The top-down approach is more complex than the bottom-up approach when
developing a large application, but it can be very useful when you are trying to
quickly create requesters to show screens and screen navigation to the end user using
the simulation feature of Pathmaker product. The top-down approach for completing
a Pathmaker application is illustrated in Fig. 3-2.