4gl's
Reasons for | Basic features (Non-procedural) | Desirable components | Products classified as | Ideal

Features

A 4GL produces an application for a particular task an order of magnitude faster than a 3GL.

For example: A database, combined with forms, reports, macros and programs could be considered a 4GL if they produce an application such as stock control.

Reasons for 4GL's

4GL's have resulted from the need for the following:

Fast interactive tools, to clear application backlogs

Increased programmer productivity

Allow for modern systems development cycles, to break free from some of the restrictions of the traditional systems development life cycle ie. serial nature, reliance on pre-specification techniques (pre-defined document), locks users in before all requirements may be known.

up-to-date tools & techniques, available for programmers

Reduction in the costs of producing software

End-user Involvement in the development process (prototyping)

Basic features

Create an application an order of magnitude faster than high level languages (such as COBOL)
Prototyping with DP Professional and end-user
Be easily learnt and remembered
Martin [Ref 72] proposed a two day learning curve
Be understood and useable by both DP professional and to the end-user
Non-procedural (WHAT has to be accomplished, rather than HOW (procedural))
Usually contain the following components
* Computer Assisted Software Engineering (CASE) tools
* Help facilities
* Non-procedural query languages
* Documentation facilities
* Application generators

Non-procedural languages

WHAT has to be accomplished

Specification Languages

Specify only what the desired results will be

Through the passing of parameters by means of form-filling or similar technique

Concerned with definition of data & the link between them

Desirable components

Database management system
Data dictionary
Query language
Report generator
Screen definition or screen painter
Graphics facilities
Decisions support &/or spreadsheet &/or statistical facilities
Application development facility (either 3GL or 4GL)
Other facilities eg. PC to mainframe links, or on-line help facilities etc.

Products classified as 4GLs

Products that have been classified as 4GL's (amongst others !) include:

Query languages
Report generators
Application builders
Very high level languages (you can include macro languages in products such as MS-Excel)
Decision support tools
Program generators
Database-oriented tools

The "ideal" 4GL

High level computer language
Single vocabulary and syntax
Defines ALL components of application development and processing
eg. DEFT ( a program/tool/language generator, where you begin with the data flow diagrams and can write scripts for ORACLE etc.)