How to Set the Type of an Attribute

Types serve to restrict the set of valid values the attribute can take, and will be one of the basic types, a restriction or another fact. The basic types have been predefined as:

• String: any combination of alpha-numeric characters, plus the _ and $ characters only
• Integer: whole numbers in the range -2147483648 to +2147483647
• Real: all numbers in the range 4.94e-324 to 1.798e308
• Boolean: the words true or false
• Date: numerically expressed in the European format: dd/mm/yyyy, (i.e. 2 digits for day/ 1 or 2 for month/4 for year). Terms can also be separated by dashes, i.e. dd-mm-yyyy. ZEUS is millennium compliant.
• Time: numerically expressed using the 24-hour clock format, as either hh:mm:ss, (i.e. 1 or 2 digits for each of hours:minutes:seconds). Seconds can be omitted, and hh:mm used instead.

Restrictions are custom types used to further restrict the values taken by the basic types. These are entered separately, see How to Create a Restriction.

When attributes need to assume more complex values, their type can be specified as a particular fact. All previously entered facts are listed under the "Facts" node of the type selection window.

• Double-click on an entry in the Attribute Table, this will summon a window showing all a hierarchy of currently known types.
• Then select the type required and click the OK button.