dBASE Plus offers a verity of data access objects for linking forms and reports to the data stored in your tables. The objects that you will use in this course are the Query object, Rowset object, Field object, and Database object. A datamodule is a dBASE container used for handling the data access objects. Usually a datamodule is stored in a separate file (with a dmd or cdm extension) and the datamodule object is used in a form or report. A datamodule enables you to re-use your data access objects on more then one form or report. In addition, you can create one set of business rules and share them across an entire application.

Readings

An Overview of OODML

"An Overview of OODML" is authored by Alan Katz, and provides an excellent conceptual overview of the "Object Oriented Data Manipulation Language" (OODML) used in dBASE.

Beginning Data Objects in Visual dBASE 7

"Beginning Data Objects" by Ken Mayer provides a detailed look at each of the data access components and explains a bit about how they are used.

Code Tips, Tricks and Advice

This document contains a variety of progrmming tips. Some of the sections are related to data access objects, while other sections are related to different topics. For the current Session of the course, you should read the following Sections. (There is a table of contentents at the beginning of the text.)

• lookupSQL
• Relating Tables
• Finding Data

Tutorial Project

Phase III: Create the Data Modules

In Phase III of the Tutorial you create the datamodules that will be used in the Tutorial application. In addition, you will create some lookupSQL files, some calculated files and some field validation.

Hands-on Project

Create the Data Modules

The Hands-on Project will also use datamodules. Here you will create the datamodules that are used in the Hands-on Project. However, you will need to create these classes without step-by-step guidance.