flex Expert System Toolkit - LPIS

5. Questions And Answers 52
Customized Input
The range of standard questions provided will inevitably not cover all
possible situations. For this reason, flex allows customized questions in
which the programmer can specify both how to obtain an answer, and what
form that answer should take. The onus is totally on the programmer to
present the question to the user (for example create a dialog) and to return
the appropriate answer. This is indicated by the KSL keyword answer.
question my_question
answer is K such that ask_my_question( K ) .
In this case no predefined dialog will be presented, but a call will be made to
ask_my_question/1: this may be defined as a flex action, a flex relation
or as a Prolog predicate. It should ask the question, creating any necessary
dialogs, and return a value for the variable K.
Default Questions
When developing an application, it is often useful to delay the exact
implementation of questions until some later stage. During this development
process, flex allows you to declare a default question which is used in the
absence of a specific definition. The name of the default question is
catchall.
question catchall
Please enter data ;
input name .
Whenever a question is asked for which there is no definition, the
catchall definition is used instead. In this case, the default answer will be
of type name.
Explaining Questions
In addition to the form of a question, you can optionally attach an
explanation to any of the standard question types (as you can with rules)
using a because clause.
The explanation itself can either be some canned text to be displayed, or it
can be the name of a file to be browsed over. The explanations are
presented whenever the end-user requests them (usually there is an Explain
button in the built-in question dialogs).
flex toolkit