TurboIMAGE/XL Database Management System Reference Manual (30391-90012)

62 Chapter3
Defining a Database
Database Description Language
Database Description Language
The database description, called a schema, can exist in the MPE/iX system as an ASCII
file. Regardless of the actual physical record size of the file, the Schema Processor reads,
prints, and processes only the first 72 characters of each record. Any remaining character
positions in the record are available for your convenience, to be used for comments or
collating information. The database description language is a free-format language; you
can insert blanks anywhere in the schema to improve its appearance, except within
symbolic names and reserved words.
Language Conventions
The conventions used in describing the database language are the same as those described
on the conventions page at the beginning of this manual. In addition, these conventions
apply.
Schema Structure
The overall schema structure is:
BEGIN DATABASE
database name [,LANGUAGE: language ];
PASSWORDS:
password part
ITEMS: item part
SETS: set part
Table 3-1. Additional Conventions
Convention Description
Punctuation All punctuation appearing in format statements must appear exactly as
shown.
Comments Comments take this form: <<comment>>
Comments can contain any characters and can appear anywhere in the
schema except embedded in another comment. They are included in the
schema listing but are otherwise ignored by the Schema Processor program.
Data Names Data names can consist of from 1 to 16 alphanumeric characters, the first of
which must be alphabetic. Characters after the first must be chosen from this
set:
Letters A through Z, digits 0 through 9, or + − * / ? ‘ # % & @
Upshifting All alphabetic input to the Schema Processor is upshifted (converted to
uppercase) with the exception of passwords which can contain lowercase
characters. Because the Schema Processor upshifts alphabetic characters,
programs must specify data set and data item names in all uppercase
characters. Take note of this if the programming language you use does not
require uppercase characters.