Visual DataFlex

Visual DataFlex is a 4GL windows programming language by Data Access, targeted at creating database and client-server type programs.

Architecture

Visual DataFlex has a 3-layer architecture:

Bottom layer

At this level you have the database tables.

Middle layer

Here you have Data Dictionary classes which are the core of the product. Data Dictionaries define the business rules for each table in your database. For example, when orders are saved a customer's balance can be adjusted and the balance tested against the customer's credit limit. An error can be raised if the customer's balance would exceed the allowable credit limit. Rules for saving, editing, deleting, or finding records are defined too. For example, you may not be allowed to delete an inventory item because there is history for it i.e. there are sales or purchases of the item. Finding of certain records can be limited to users who have the required credentials.

Top layer

A graphical user interface (GUI) that allows users to enter, find, create, modify, or delete data. The UI will respect all of the business rules defined in the Data Dictionary classes.

History

Data Access Worldwide of Miami, USA is the company behind the studio and language and built its business up around the console mode DataFlex language which was released prior to DOS and competed with dBase II in early microcomputer technology. The first attempt at a windows product was DataFlex for Windows which failed as it was a sort of windows bolted on top of DOS product. Then they released Visual DataFlex 4.0 in 1997 which allowed users to write native 32 bits Windows applications. Every 6 months a new revision level is released. Visual DataFlex is now in revision 17.0, named VDF 2012, and features a datadictionary layer of business rules which is of dual use with the windows product and the webapp extension.

External links

• Official website
• vdfwiki.com
• Support forum
• Visual DataFlex open source website
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