2-01:Characteristics of the Data Dictionary

Chapter 2-1: Data Dictionary Overview

Characteristics of the Data Dictionary

There are four principal attributes that characterize the APPX data dictionary. The dictionary is:

· Active, in that its specifications are used by, and place real time restrictions on, both designers creating applications and users operating them. An active data dictionary maximizes consistency, productivity, and integration. It minimizes the chance for error, both when designing and using applications. For example, assume you have defined a numeric, five-character zip code field. APPX uses the length specification to provide a proper mask for the designer who is painting the field on an input image. APPX also uses data dictionary specifications as a basis for data validation when the image is executed. The system displays an error message if the application user attempts to enter a Canadian postal code (containing letters) into the numeric zip code field.

· Processed, to enhance performance. The specifications you enter into the data dictionary are translated into a format more directly usable by APPX during process execution. Processing the data dictionary also searches for logic errors (invalid key definitions or illegal record lengths, for example), constructs default value records for each file, computes field lengths, and establishes the starting position for each field within a record. Refer to Processing the Data Dictionary in Chapter 2-2 for more information.

· Internally documented. The dictionary provides entry screens for the online help text and printed technical documentation. Documentation is an integral part of APPX development and user interface.

· Automatically monitored for structural changes, to ensure integrity. If you make such a change to the dictionary, all processes that reference changed elements are automatically updated, including images and event points. APPX flags existing data files that require restructuring, and permits you to automatically convert them to the new structure with the restructure utility in database management.

APPX Application Design Manual (01/13/03)