Constraints between objects

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Constraints between objects

In general, our modellers and other users of Web-O-Matic are likely to be more interested in the interactions between objects than in single objects. As a simple example, suppose that a Web form is to contain a field into which an integer can be entered, as above. When the form is submitted, the integer will be sent to a little program running on the server, which calculates its factorial and returns the result to the server. This result is then to appear as text under the field.

We could describe this in terms of objects by saying that the page contains two objects. One is an IntegerField. The other, the space for the result, is a simpler object which, when sent a value, displays it as HTML. We shall call this a Text, and we can describe its behaviour thus:

Then the entire page has the description:

There is no reason why all the related objects have to sit on the same page: the concept clearly extends to relations between objects on different pages.

Jocelyn Ireson-Paine
Sat Oct 12 23:35:52 BST 1996