Unidirectional and bidirectional relationships

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A relationship describes the dependency or connectivity between configuration items. A relationship can be either unidirectional or bidirectional. The results of a search are affected when relationships are bidirectional or unidirectional.

Unidirectional relationships

A unidirectional relationship is valid in only one direction. The following phrases are examples of unidirectional relationships: installed on, installed with, contains, member of, starts from, resides on, succeeded by, and preceded by.

For example, an operating system is installed on a computer. A computer is not installed on an operating system. However, in another type of unidirectional relationship, you can specify that a computer contains an operating system.

Bidirectional relationships

A bidirectional relationship is valid in both directions. Intersects is an example of a bidirectional relationship.

Search results

The distinction between unidirectional relationships and bidirectional relationships is important when you search configuration items based on relationships.

Relationship	Search results
Bidirectional	A user searches for all configuration items with an interfaces with relationship to application Z. Since interfaces with is a bidirectional relationship, the search program searches for these occurrences: The source configuration item is application Z and the relationship is interfaces with. The target configuration item is application Z and the relationship is interfaces with.
Unidirectional	For unidirectional relationships, the search program searches for one combination. For example, a user searches for all configuration items with a member of relationship to an EMAIL SERVICE application, where EMAIL SERVICE is the target configuration item. The search program searches for the following occurrence: the target configuration item is EMAIL SERVICE and the relationship is member of. You can define one unidirectional relationship to be complementary to another unidirectional relationship. For example, in your relationship definition, you specify that installed on is complementary to installed with. A user wants to find all configuration items that are installed on AppServer K. The search program searches for these occurrences: The target configuration item is AppServer K and the relationship is installed on. The source configuration item is AppServer K and the relationship is installed with.

Relationship

Search results

Bidirectional

A user searches for all configuration items with an interfaces with relationship to application Z. Since interfaces with is a bidirectional relationship, the search program searches for these occurrences:
- The source configuration item is application Z and the relationship is interfaces with.
- The target configuration item is application Z and the relationship is interfaces with.

Unidirectional

For unidirectional relationships, the search program searches for one combination. For example, a user searches for all configuration items with a member of relationship to an EMAIL SERVICE application, where EMAIL SERVICE is the target configuration item. The search program searches for the following occurrence: the target configuration item is EMAIL SERVICE and the relationship is member of.
You can define one unidirectional relationship to be complementary to another unidirectional relationship. For example, in your relationship definition, you specify that installed on is complementary to installed with. A user wants to find all configuration items that are installed on AppServer K. The search program searches for these occurrences:
- The target configuration item is AppServer K and the relationship is installed on.
- The source configuration item is AppServer K and the relationship is installed with.