In addition to supporting an unparalleled range of physical field types, Arbutus also supports virtual fields, referred to as computed fields. Computed fields are implemented by Arbutus purely as definitions, there is no physical data actually created, and no pre-processing delays. Once defined, computed fields are automatically exposed through Legacy Link and can be used just like a physical field. As a simple example, if you had an inventory file that contained physical fields specifying the quantity on hand (QTY) and the unit price (PRICE), then you can define a simple computed field VALUE with the definition QTY*PRICE. As soon as the field is defined you can refer to VALUE as if it were a physical field in the file, as Legacy Link does not differentiate between physical and computed fields. While the above example is very simple, computed fields can contain the value of any expression, regardless of complexity.