Inside Windows-Update

The query argument specifies the level of detail of the information to be returned. In the observed messages four different levels are used - Provider, Products, Items, and DriverUpdates.

Provider - The Microsoft server returns all product categories for which it supplies updates, e.g. ie60x for Internet Explorer 6.x or winxp for the various versions of Windows XP, and rules for determining whether a product that belongs to a specific category is installed. The rules are boolean expressions written in a simple XML-based language. For instance, the rule for product category ie60x is that one of the products that belong to the product category ie60x is installed if the registry value HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Internet Explorer\\Version is lower than 7.0 and higher than or equal to 6.0.

Products - The query argument contains a list of product categories and the Microsoft server returns the products that belong to each product category, e.g. winxp.windowsxpcore for the components of Windows XP that are shared by all versions, winxp.windowsxp for the components specific to the professional edition and the home edition of Windows XP, or winxp.windowsnetserverfamily for the components specific to the .NET server edition.

Items - The query argument contains a list of products and the Microsoft server returns detailed information about the updates that are available for each product.

DriverUpdates - The Microsoft server returns a list of driver updates that are relevant for the computer that is being updated. Note that the SOAP messages for calls to GetManifest at this level are several times as long as the other observed SOAP messages.

Provider, Products, and Items form a hierarchy. Windows Update first asks the Microsoft server at the Provider level for the supported product categories. It then determines which of the product categories are relevant for the computer that is being updated by evaluating the rules returned by the server. Based on this, Windows Update then asks the server at the Products level for the products contained in each category. It then determines which of the products are relevant for the computer that is being updated, again by evaluating the rules supplied by the server. Finally, Windows Update is able to ask the server at the Items level for details about the available updates for the relevant products.