## 4.6.2 Definition

The Requires is a concrete ReferenceType and can be used directly. It is a subtype of HierarchicalReferences.

The semantic of this ReferenceType is to relate a component to other components it requires in order to work.

The SourceNode of References of this ReferenceType shall be an Object or ObjectType representing a component that requires the TargetNode in order to work.

The TargetNode of References of this ReferenceType shall be an Object representing the required component used by the SourceNode.

Requires References shall not lead to loops, that is, starting from Node “A” and only following References of ReferenceType Requires or subtypes it shall never be possible to return to “A”. But it is allowed that following the References there may be more than one path leading to another Node “B”.

Requires is formally defined in Table 5.

Table 5 – Requires Definition

Attributes Value
BrowseName Requires
InverseName IsRequiredBy
Symmetric FALSE
IsAbstract FALSE
References NodeClass BrowseName Comment
Subtype of HierarchicalReferences defined in OPC 10000-5
Conformance Units
Base Info Requires