WMI: The Industry Picture

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[oR]

The need for system instrumentation and configuration is not unique to device drivers, Windows 2000, or Microsoft. The Open Software Foundation (OSF) includes a task group, the Desktop Management Taskforce (DMTF), that has published an initiative for unified system management compatible with Internet standards, Web-Based Enterprise Management (WBEM).

WBEM defines an interface for the purpose of unified management and instrumentation: the Common Information Model (CIM). CIM is designed to encapsulate and accommodate other industry initiatives such as the Simple Network Management Protocol (SNMP) and the Desktop Management Interface (DMI).

CIM is a very general-purpose way of describing properties, methods, and events that clients can use to efficiently obtain system-supplied data. WMI is Microsoft's implementation of WBEM. Therefore, it is based on CIM and extends itself to components within Windows 2000 to provide a functional environment for management and instrumentation.

CIM defines a new language (actually an extension of C) called MOF (Managed Object Format). MOF is loosely based on the Interface Definition Language (IDL) familiar to users of Remote Procedure Calls (RPCs) and Microsoft COM (Component Object Model).

A diagram that describes the relationship between WBEM and WMI is shown in Figure 13.1.

Figure 13.1. WBEM and WMI relationship.

Acronym overload aside, MOF is the language by which the provider and the consumer can precisely communicate and exchange data. For example, a data definition within the MOF file to describe the total packet count transferred by a driver might appear as follows:

 [read, WmiDataId(1),      Description("Total Packet Count")]      uint64 PacketsTransferred; 

A client application, having been built with knowledge of the MOF contents, is now aware that the packet count is available from the provider as a 64-bit unsigned integer.

The advantage of conformance with industry standards for system management and instrumentation is obvious: heterogeneous system integration. With sufficient industry acceptance and conformance, Microsoft-based, Linux, and mainframe systems can cooperate in a peer-to-peer configuration, management, and reporting environment.

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