Requests for Comments (RFC) 1155 and 1213 define the Management Information Base (MIB) as an object-oriented database. Both RFCs refer to the node names as object identifiers. Most nodes also have descriptive textual names called object descriptors. The object descriptors are convenient aliases, but Simple Network Management Protocol (SNMP) request packets refer to variable instances only by object identifier. Variable names and variable instances are both denoted by object identifiers or object descriptors. To distinguish the four possible combinations unambiguously, the following non-RFC terminology is used here:
| Terminology | ||
| Non-RFC Terminology | RFC Terminology | Example |
| Text-format variable name (denotes the descriptive textual name of a variable) |
Object descriptor of a variable | sysDescr |
| Numeric-format variable name (denotes a variable name expressed as a sequence of decimal numbers separated by periods) |
Object Identifier of a variable | "1.3.6.1.2.1.1.1 |
| Text-format instance ID (denotes a text-format variable name qualified by an instance) |
Object descriptor of a variable with an instance appended | sysDescr.0 |
| Numeric-format instance ID (denotes a numeric-format variable name qualified by an instance) |
Object identifier of a variable with an instance appended | "1.3.6.1.2.1.1.1.0 |
Instance IDs are variable names with an instance appended. A variable name refers to a set of related data, while an instance ID refers to a specific item from the set.
For information on the subroutines, see "List of SNMP Agent Programming References".