Object identifier
In computing, an object identifier or OID is an identifier used to name an object (compare URN). Structurally, an OID consists of a node in a hierarchically-assigned namespace, formally defined using the ITU-T's ASN.1 standard, X.690. Successive numbers of the nodes, starting at the root of the tree, identify each node in the tree. Designers set up new nodes by registering them under the node's registration authority. The root of the tree contains the following three arcs:
0: ITU-T
1: ISO
2: joint-iso-itu-t
In computer programming, an object identifier generally takes the form of an implementation-specific integer or pointer that uniquely identifies an object. However, OIDs are a specific approach to creating globally unique object identifiers in a distributed system.
Usage
In computer security, OIDs serve to name almost every object type in X.509 certificates, such as components of Distinguished Names, CPSs, etc.
Within X.500 directory schemas and protocols, to uniquely name each attribute type and object class, and other elements of schema.