1.5 Summary

Because a class is a template that represents a manageable entity from the real world, made accessible with a provider, mastering the provider capabilities with its classes is a determinant factor when developing applications on top of WMI.

Although our class classification is made by WMI providers, Microsoft, in its Platform SDK, classifies the classes by role. This classification regroups the classes that are related to the same parts of the system independently of the WMI provider supporting them. This difference comes from the fact that Microsoft estimates that it is not necessary to know and understand the provider implementation to work with the classes they support. This statement is true in a sense, but having a rough idea of the provider capabilities, such as determining if it is implemented as an event provider or an instance provider, can help people to determine how a WQL event query must be formulated (use of the WITHIN statement for dynamic instance classes or not using the WITHIN statement when an extrinsic event class is referenced in the query, as it is supported by an event provider).

When installing Windows Server 2003, WMI is part of the installation and it comes with an important number of WMI providers and classes. Although we can list the classes available from the providers, it is impossible to list each class properties in a single book, but the helper scripts (LoadCIMinXL.wsf, LocateProviders.wsf, GetSingleInstance.wsf, GetCollectionOfInstances.wsf) can be used as tools to complete the discovery. From a manageability perspective, Windows Server 2003 represents a major step for the Enterprise because it offers much more WMI management capabilities than Windows 2000. Besides the WMI functionalities part of the Operating System installation, Windows applications such as Exchange 2000, SQL Server 2000, and HP OpenView Operations for Windows (OVOW), to name a few, bring their own providers and enhance the WMI capabilities. This means that there is no limit to the WMI discovery, since each new piece of software can extend the WMI capabilities. This is where the helper scripts become interesting, since they can help you discover information not necessarily documented in an SDK.

In this chapter, we learned that the WMI provider discovery technique helps us to understand the WMI provider types available, to structure their roles and the classes they support, since each provider brings its own set of capabilities with a certain number of classes. Now, the next step is to examine each of them with their own set of classes with their capabilities. Therefore, in the next chapter, we will pursue the discovery by exploring the Win32 providers, which serve as a great example since they support the largest number of classes available from WMI.