Alias

Example

The above picture shows part of an example database specification. The example contains an entity Relation. There is a recursive relation contained in this entity. Each Relation can have an optional Partner that also is a Relation.

The entity Relation contains a recursive relation "is partner of". To express this relation in the DID you can define an Alias for an Entry. Such an Alias is an alternative name for an Entry. The Alias Entry can be used as a Subentry. We can now write WITH Partner IN Relation.Partner instead of WITH Partner IN Relation.Relation. The first alternative is clearer.

An Alias can also be useful if you want to use a certain Entry twice as a Subentry. For example, an Entry Relation has a Field Postal_Address and a Field Visiting_Address. Both Fields contain an address number. This address number serves as a formal parameter for an Entry Address. You could then make two Aliases Postal_Address and Visiting_Address for the Entry Address. You can then use these Aliases as Subentries in the Entry Relation. For the Subentry Postal_Address, you define the Field Postal_Address as the actual parameter. For the Subentry Visiting_Address, you define the Field Visiting_Address as the actual parameter. This is shown in the picture below.

An Alias is an alternative name for an Entry.