Unit set objects

Many databases have systems of units, such as currency and weight. You can define those units using unit set objects. Once you have defined the appropriate unit set objects, you can create instances of the units such as a pile of coins or use the unit set as the basis for properties in an object.

A unit set consists of any number of units related to each other with a value property. Each unit consists of the unit's name, plural name, abbreviation, and value. The plural name property is optional; if you leave it empty, the plural will be assumed to be the name plus an 's'.

Typically, you will want one of the units in the set to have a value of 1, denoting the base unit. If no unit has a value of 1, the default unit is the one whose value is logarithmically closest to 1. For example, if a unit set consists of two units, one with a value of 0.1 and the other with a value of 2, the unit with a value of 2 becomes the default unit. The base unit is displayed in bold face.

Unit Objects

Often, especially with currency unit sets, you will want to create objects that are physical representations of a unit in a set. To do this,

Choose Catalog from the Windows menu. This opens the Catalog window if it isn't already open and brings it to the front.
Double-click "Object" in the list of object types. The object is created. Now, we'll tell the object to use a unit value as its name.
Select the unit object.
Choose Edit Properties from the Object menu. The Properties window for the object is opened.
Select the Name property and choose Edit Properties from the Object menu, or double-click the Name property.
Select Unit from the Show As pop-up menu. This tells the object to display its name as a unit value.
Pick the appropriate unit set from the Unit Set pop-up menu; this menu contains a list of all unit sets in all open documents.

The object is now a unit object. Close the Properties window.

To change the value of the unit object,

Select the Name property by clicking on its name in the contents view.
Move the cursor out of the property or press Return; the property becomes a text entry box.
Type the new value as a number and, optionally, the name of the unit from the unit set and press Return to set the value.
The value in the list is changed to reflect the value and the edit property is removed. A unit from the unit set is chosen for the value based on what you enter. If you entered a unit name or abbreviation, that unit is chosen. Otherwise, the unit set's default unit is chosen.

Combining unit objects

You may want to combine a series of unit objects into the least amount of units possible. For example, you may have a set of currency objects and want to convert them all to the least possible number of coins. To combine unit objects:

Select the unit objects. Every object selected must have their Name property set to be shown as a unit referencing the same unit set object.
Choose Combine Unit Objects from the Object menu.

The unit objects are deleted and a new set of unit objects are created which represent the least number of objects to represent the same total value.

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