Pathmaker Programming Guide

Defining Data for a Pathmaker Project
Preparing for Pathmaker Application Development
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Using Enscribe DDL for NonStop SQL Data
Occasionally, you need to create Enscribe DDL definitions for use in a NonStop SQL
application. Situations where you might do so include:
The Pathmaker product does not allow you to pass a single column of a table from
a requester and to a single column of a service. This restriction means that even if
you need data from only one column, you must pass data for the entire table if you
use only NonStop SQL.
To pass a single column, create a DDL definition of the same length and type as
the column you want to pass. Add the DDL definition to the IPC Definition screen
of the service. Now, when defining a requester that accesses that service, you can
match the column name to the DDL definition on the SEND Parameter Definition
screen. Note that you must qualify the column name with the table object name
on the SEND Parameter Definition screen. For example, if the table object name is
OBJECTNAME and the column name is COLUMNNAME, you would enter the
qualified column name this way on the SEND Parameter Definition screen:
OBJECTNAME.COLUMNNAME
In NonStop SQL, data is organized as tables; you cannot refer to a common
definition for a column that is included in more than one table. There is no
inheritance structure where one definition can take on characteristics of another.
If you are creating a tabular screen, that is, a screen that lists information in one or
more columns, you can create an Enscribe DDL definition using the OCCURS
clause to describe the screen. You can use this structure to pass data to and receive
data from the service. This use of Enscribe DDL is discussed in more detail later in
this section.
You can use Enscribe DDL to create a data field that is never sent to a service. For
example, you can create a screen data field to provide data for custom requester
code in the requester copy library.
Note If you create definitions in Enscribe DDL, you can use the SQL CONVERT utility to convert the Enscribe
files described in a DDL dictionary to tables described in a catalog. CONVERT, however, ignores a
number of Enscribe DDL clauses, including MUST BE. You can restrict the values that can be inserted
into a column by adding CREATE CONSTRAINT commands.
See the NonStop SQL Conversational Interface Reference Manual for a complete list of clauses ignored
by CONVERT and for a description of how to use the utility.
Enscribe DDL does not support the DATETIME and INTERVAL data types; if you want to use either of
these data types in your application, you must write the data description for the table by using SQL DDL.
Although it might not be necessary, you might prefer to create an Enscribe DDL
schema that contains:
All data items not found in the NonStop SQL database
A DEF for every data field found in the NonStop SQL database