Goals and Means of Visual Prolog 7 Language Update

The goals of the language update are to provide better means for creating and maintaining more complex programs for more complex surroundings.

Simplicity

Humans are better to dealing with simple things than complex things, so one important way to deal with complexity is to reduce it to something simpler, especially by using "structure" to organize the complexity.

The main "trick" is the divide and conquer principle: Divide the original problem into separate sub-problems that can be solved individually.  I.e., the solution to the overall problem consists of a number of sub-solutions and something that combines these into the overall solution.

Maintainability

For software it is often not enough to solve a problem, we must also be able to maintain and extend the solution in an evolving world.  So it is important that the used methods not only solve the problem, but also result in a program that can be maintained.  Here it is important that the program is understandable and especially that the divides are visible and clear in the program.

Reuse and Sharing

When you divide problems into sub-problems, perhaps repeatedly, you will sometimes see similar sub-problems.  Then it would of course be nice to short cut by reusing a similar solution.  Such a solution can be adopted into the new context, but there are two ways this can happen. We can make a copy and update it to its new purpose, or we can try to share the code between the two problems.

The latter is clearly the hardest and only makes sense if both pieces of software are still maintained.  But in that case you will have the advantage that maintenance made in one context is also shared with the other context.

Flexibility

It is also desirable that your software is flexible.  You may for example need to deliver several variants of your software to different customers.  Or you may need to reconfigure the software to a changed context.  Also some of your shared sub-solutions may need to go into contexts that are not completely the same.

Power

Finally, it is of course desirable if language extensions add additional programming power.  For example, by simplifying the code necessary to tackle certain standard "issues".