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Compound

Introduction

A compound box is a box which contains a set of other boxes. Compound boxes allow a set of boxes to be bracketed as a single functional unit. They behave in the same way as all other boxes when they are being drawn and manipulated, but can be opened to reveal a new window in which further boxes may be drawn. The set of boxes which comprise the compound may be drawn in this window in exactly the same way as boxes were drawn on the compound's parent's window.

Any model can actually be thought of as a compound box, and opening a compound reveals a new window much like the main window. However, the window associated with a compound differs from the main window in one important way: it contains "virtual" boxes, drawn with dotted lines, representing those boxes to which the compound is externally linked. Arrows may be drawn to and from these external objects, enabling boxes within the compound to communicate with those outside of it.

There are several things which you might want to do with compounds but which cannot as yet be done. It is not possible, for example, to "rubber-band" a set of boxes and transform them into a compound. Conversely, it is not possible to "explode" a compound, so that all boxes within a compound return to the compound's parent. However, it is possible to cut and paste boxes between compounds (just as you can cut and paste subobjects between any pair of boxes of the same class). Since a model can be thought of as a compound box, this facility means that you can cut objects from the main window and place them in a compound, or you can cut them from a compound and place them on the main window. It is also possible to cut and paste objects between different models.

Editing Compounds

A window displaying a compound box has an Initial Contents tab which allows the user to add and delete boxes and arrows and to move boxes. Once the Initial Contents tab has been selected the following operations may be performed.


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