Introduction to Data Management

Developing Applications With PATHMAKER
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Application
Components
When you begin your development effort, PATHMAKER creates a project, which is a
framework that allows the application to run under control of the PATHWAY
transaction processing system. The PATHWAY environment includes the requesters
that manage the terminal interface and the servers that manage the database, both
supplied by your application. The PATHWAY environment also includes several
other processes that PATHWAY supplies to support your application. These
processes communicate with each other through messages transmitted through the
message system portion of the GUARDIAN 90 operating system. The PATHWAY
environment is explained in detail in Section 6.
Your requester program interacts with the end user under control of a PATHWAY
terminal control process (TCP), as shown in Figure 5-1. The TCP runs your program,
which translates the end user’s input into requests for action by a server. The
requester program contains presentation logic for a single logical screen (which can
contain many pages), manages terminal context associated with that screen,
communicates with servers, and handles navigation to other requester screens.
PATHMAKER generates requester programs based on the information you supply
through PATHMAKER screens, using a standard file of SCREEN COBOL code. The
logical screen associated with the requester defines the locations, lengths, and other
attributes of fields displayed on the user’s terminal screen.
Figure 5-1. Requester Passing User Requests to a Server
S8020-016
Server
TCP
Requester
Screen
Within a server, an entity called a service defines a particular transaction to be
performed on the database. The service is one module of the server program. Each
service can perform various database operations, plus other functions typically
available through the COBOL language.
PATHMAKER supplies a set of standard services that perform simple I/O tasks like
reading the next record or inserting a record, in much the same way as ENABLE does.
But in most cases, you will want to create your own custom services; these services,
for instance, might perform a series of related operations.