Visual DataFlex
Encyclopedia
Visual DataFlex is a 4GL windows programming language
by Data Access, targeted at creating database
and client-server type programs.
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.
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 16.1, named VDF 2010, and features a datadictionary layer of business rules which is of dual use with the windows product and the webapp extension.
Programming language
A programming language is an artificial language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine and/or to express algorithms precisely....
by Data Access, targeted at creating database
Database
A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...
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
Gui
Gui or guee is a generic term to refer to grilled dishes in Korean cuisine. These most commonly have meat or fish as their primary ingredient, but may in some cases also comprise grilled vegetables or other vegetarian ingredients. The term derives from the verb, "gupda" in Korean, which literally...
) 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 DataFlexDataflex
DataFlex is a relational database management system, self-described as an applications development database, originated around 1980.It is a relatively early example of a fully fledged and commercially used fourth-generation programming language . In its early forms, DataFlex was available for UNIX,...
language which was released prior to DOS
MS-DOS
MS-DOS is an operating system for x86-based personal computers. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for IBM PC compatible personal computers during the 1980s to the mid 1990s, until it was gradually superseded by operating...
and competed with dBase II
DBASE
dBase II was the first widely used database management system for microcomputers. It was originally published by Ashton-Tate for CP/M, and later on ported to the Apple II and IBM PC under DOS...
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 16.1, named VDF 2010, and features a datadictionary layer of business rules which is of dual use with the windows product and the webapp extension.