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Understanding the WMI Model

WMI provides access to information about the managed objects that make up your computer systems. To service information requests, WMI uses a hierarchical namespace, in which the layers build upon one another like the folder structure on your hard disk drive. These namespaces are used to organize the objects. For example, there is a RSOP namespace that is used to provide access to Resultant Set of Policy information, and there is a MicrosoftDNS namespace that allows you to work with Domain Name System (DNS). Although it is true that WMI is a hierarchical namespace, the term doesn't really convey the richness of WMI. The WMI model has three sections that you need to be aware of: resources, infrastructure, and consumers (see Figure 8-1). The use of these components is listed below.

  • WMI resources Resources include anything that can be accessed by using WMIthe file system, networked components, event logs, files, folders, disks, Microsoft Active Directory directory service, and so on.

  • WMI infrastructure The infrastructure comprises three parts: the WMI service, the WMI repository, and the WMI providers. Of these parts, WMI providers are most important to network administrators because they provide the means for WMI to gather needed information. If the provider does not exist, then none of the classes will exist. (This is common on Windows Server 2003, because the MSI Provider is not installed by default. This means the WIN32_Product class is not available, because it relies upon the MSI Provider.)

  • WMI consumers A consumer "consumes" the data from WMI. A consumer can be a script written in VBScript, an enterprise management software package, or some other tool or utility that executes WMI queries.

    Figure 8-1. Components that make WMI work


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