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Relationship Types A relationship type is a template for defining relationships in the dictionary. A relationship type has three parts: * An ordered entity type list. * A relationship class. * An attribute list. Like an entity type, you can think of a relationship type as a category or grouping. Relationships between IMAGE data bases and data sets are grouped under the relationship type IMAGE-DATABASE contains IMAGE-DATASET. You can also view a relationship type as a qualifier. The entity type list of the relationship type qualifies the entities in the relationship. You can have multiple relationships between entities named ORDERS and INVENTORY provided you qualify them by different relationship types. Specifying Entity Type Lists A relationship type does not have a name. It has a list of names representing the entity types involved in the relationship type. Before you can create a relationship type, all the entity types in the entity type list must already exist. Also, you cannot delete one of the entity types involved with the relationship type unless you explicitly request that all the relationship types involving that entity type are to be deleted. Specifying Relationship Classes In System Dictionary, a relationship type is qualified by relationship class. The relationship class describes the connection or action of a relationship. In the relationship type IMAGE-DATABASE contains IMAGE-DATASET, for example, the relationship class is contains. It expresses the fact that, in each relationship of this type, the first entity contains the second. To create a relationship type, you must specify a relationship class that already exists in the dictionary. You cannot delete a relationship class without explicitly requesting the deletion of all the relationship types of that class. Specifying Attribute Lists Relationship types have attribute lists such that each relationship of the type must have a value for each attribute in the list. Every relationship type has six built-in attributes, called special attributes (special attributes are discussed later in this chapter). When you create a relationship type, System Dictionary automatically associates these attributes with the new relationship type. In addition, each relationship type may have other attributes associated with it. For each attribute in a relationship type's attribute list, there must be a corresponding attribute value assigned to each relationship of that type. You can add attributes to a relationship type's attribute list by creating type-attribute associations (discussed later in this chapter). Creating and Accessing Relationship Types You can create, delete, modify, and retrieve relationship types. Detailed instructions for doing these operations are located in other HP System Dictionary/XL manuals. Refer to the HP System Dictionary/XL SDMAIN Reference Manual (32256-90001) for instructions to do these operations with the System Dictionary user interface, or to the HP System Dictionary/XL Intrinsics Reference Manual (32256-90002), if using the System Dictionary intrinsics.