Relationships Among Objects

The Cadence database stores many predefined relationships among different types of objects. Some relationships are automatically kept by the database, while other inter-object relationships must be explicitly created and maintained by applications.

Some relationships in the database are mandatory, for example, each terminal must be attached to a net. Application programs cannot, therefore, create a terminal without specifying the net it connects to. Mandatory relationships are often unidirectional; for example, it is acceptable to have a net that does not connect to a terminal.

Some relationships in the database are optional. Objects can be created independently now with a relationship created later by an application.

When a predefined relationship is one-to-one or many-to-one, there is an access function (in the form of a pseudo-attribute) to go from the source object to the object it relates to. When a predefined relationship is a one-to-many relationship, there is an access function (in the form of a pseudo-attribute) that returns a list of the objects contained in the relationship.

Related Topics

Data Stored as Objects