The traditional technology

Traditionally, configurators are built from a product model by the use of a complex piece of dynamic search software, often referred to as "constraint propagation.

Constraint propagation

Constraint propagation is based on research dating back to the 1960s within the research area of computer science called artificial intelligence.

The search software provides guidance by initiating a search through the rules each time the user makes a selection. The result of the search is used to update the information the configurator provides to the user. The following figure illustrates how the search software reads the rules and interacts with the user through the configurator.

Complex and no guarantees

Although dynamic search has many useful applications, there are problems with the approach. Performance of the dynamic search software is unpredictable and the formulation of the rules has a direct influence on the performance of the searches.

A consequence is that in order to obtain reasonable performance, an expert must re-engineer the rules until acceptable performance has been obtained. This gives a serious problem with maintenance of the product model because the model no longer is structured in a manner suitable for the product but rather is suitable for the search software.

That is, the model does not reflect how the persons having product knowledge and responsibility view the product. As a consequence, there is a high risk of errors being introduced in the re-engineering and that the maintenance of the model is very expensive.

Even after re-engineering, it is impossible to guarantee good performance in all circumstances. This is often tackled by setting a timeout, of for instance 1 second, and then terminate the search after the timeout without having found the exact answer and instead use an approximate answer.

Another problem is that the search software is quite complex. This limits the places in which it can be used to powerful servers and PCs. The complexity of the software further makes it very difficult to ensure that the answers are always correct.