Common Information Model (computing)
|Organization||Distributed Management Task Force|
|Related standards||WBEM and SMASH|
One way to describe CIM is to say that it allows multiple parties to exchange management information about these managed elements. However, this falls short in expressing that CIM not only represents these managed elements and the management information, but also provides means to actively control and manage these elements. By using a common model of information, management software can be written once and work with many implementations of the common model without complex and costly conversion operations or loss of information.
The CIM standard is defined and published by the Distributed Management Task Force (DMTF). A related standard is Web-Based Enterprise Management (WBEM, also defined by DMTF) which defines a particular implementation of CIM, including protocols for discovering and accessing such CIM implementations.
Schema and specifications
The CIM standard includes the CIM Infrastructure Specification and the CIM Schema:
- CIM Infrastructure Specification
- The CIM Infrastructure Specification defines the architecture and concepts of CIM, including a language by which the CIM Schema (including any extension schema) is defined, and a method for mapping CIM to other information models, such as SNMP. The CIM architecture is based upon UML, so it is object-oriented: The managed elements are represented as CIM classes and any relationships between them are represented as CIM associations. Inheritance allows specialization of common base elements into more specific derived elements.
- CIM Schema
- The CIM Schema is a conceptual schema which defines the specific set of objects and relationships between them that represent a common base for the managed elements in an IT environment. The CIM Schema covers most of today's elements in an IT environment, for example computer systems, operating systems, networks, middleware, services and storage. Classes can be, for example: CIM_ComputerSystem, CIM_OperatingSystem, CIM_Process, CIM_DataFile. The CIM Schema defines a common basis for representing these managed elements. Since most managed elements have product and vendor specific behavior, the CIM Schema is extensible in order to allow the producers of these elements to represent their specific features seamlessly together with the common base functionality defined in the CIM Schema.
- Updates to the CIM Schema are published regularly.
Many vendors provide implementations of CIM in various forms:
- Some operating systems provide a CIM implementation, for example:
- Some implementations are Independent of the systems they support, for example:
- Open Group's Pegasus
- WSI's J WBEM Server
Management Standards based on the CIM Schema
Standards organizations have defined management standards based on the CIM Schema:
- The Storage Networking Industry Association (SNIA) has heavily bought into using CIM and WBEM: they have defined their usage of CIM (called Storage Management Initiative – Specification or SMI-S) as a standard.
- Some server manufacturers collaborate in the DMTF under the SMASH initiative to define CIM-based management of servers.
- The DASH initiative in the DMTF attempts to define CIM-based management of desktop computers.
Communication protocols used
A number of protocols are defined for messages transmitted between clients and servers. The message protocols are transmitted on top of HTTP. There are two message types:
- operational messages, which provoke a response from the receiver (RPC)
- export messages, which are indications/events.
CIM Operations over HTTP (CIM-XML)
CIM-XML forms part of the WBEM protocol family, and is standardised by the DMTF.
CIM-XML comprises three specifications:
WS-MAN forms part of the WBEM protocol family, and is standardised by the DMTF.
WS-MAN comprises 3 specifications:
- WS-CIM Mapping Specification
- WS-Management CIM Binding Specification
- Web Services for Management (WS- Management) Specification
CIM operations over RESTful services
CIM-RS forms part of the WBEM protocol family, and is standardised by the DMTF.
CIM-RS comprises three specifications:
- CIM Operations Over RESTful Services
- CIM-RS Protocol Specification
- CIM-RS Payload Representation in JSON
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