About Indications

CIM events can be classified as either life cycle or process. A life cycle event is a built-in CIM event that occurs in response to a change to data in which a class is created, modified, or deleted, or a class instance is created, modified, deleted, read, or has a method invocation. A process event is a user-defined event that is not described by a life cycle event.

Event providers generate indications in response to requests made by the CIM Object Manager. The CIM Object Manager analyzes subscription requests and uses the EventProvider and/or the CIMIndicationProvider interface to contact the provider, requesting that it generate the appropriate indications. When the provider generates the indication, the CIM Object Manager routes the indication to the destinations specified by the CIM_IndicationHandler instances. These instances are created by the subscribers.

Event providers are located in the same manner as instance providers. In the case of subscriptions pertaining to instance life cycle indication (subclasses of CIM_InstIndication), once the CIM Object Manager determines the classes covered by the subscription, it contacts the instance providers for those classes. For process indications, the CIM Object Manager contacts the appropriate provider using the Provider qualifier.

The CIM Object Manager and the CIM Object Manager Repository handle indications under the following circumstances:

• The CIM Object Manager handles CIM_InstMethodCall, CIM_InstModification, CIM_InstDeletion and CIM_InstCreation events if the provider does not support indications, or tells the CIM Object Manager to poll.

• The CIM Object Manager Repository handles all class indications and life cycle indications for classes that do not have providers. These classes include CIM_ClassCreation, CIM_ClassDeletion CIM_ClassModification, CIM_InstCreation, CIM_InstModification, CIM_InstDeletion and CIM_InstRead.

In these cases, the provider does not generate indications or implement the EventProvider interface. In addition, the provider can delegate event generation responsibilities to the CIM Object Manager. The CIM Object Manager invokes enumerateInstances on the providers and compares snapshots of previous states to current states to determine if instances have been created, modified, or deleted.

In most cases, providers should handle their own indications since polling carries a high overhead. In order to generate indications, the provider itself must poll. In this case, the provider can delegate the task to the CIM Object Manager.

If a provider implements the EventProvider interface, the CIM Object Manager invokes the methods in the interface and takes actions according to the responses. When the CIM Object Manager determines that a particular provider must participate in a subscription request, the methods are invoked in the following order:

1. mustPoll - Invoked by the CIM Object Manager for CIM_InstCreation, CIM_InstDeletion, and CIM_InstModification to determine if the provider wants the CIM Object Manager to poll. If the provider does not implement the EventProvider interface, the CIM Object Manager assumes polling by default.

2. authorizeFilter - If the provider implements the Authorizable interface, this method is invoked by the CIM Object Manager to determine if the subscription is authorized. The provider can make the determination based on the user ID of the owner of the indication handler—the user who receives the indications—or based on the user ID of the user who created the subscription.

   If the provider does not implement the Authorizable interface, the CIM Object Manager performs the default read authorization check for the namespace.

   If the provider does not implement the EventProvider interface and the CIM Object Manager tries to poll, the authorization succeeds if enumerateInstances succeeds on the provider.

3. activateFilter - Invoked by the CIM Object Manager when the authorization succeeds and the provider does not want to be polled.

4. deActivateFilter - Called when a subscription is removed either by the subscriber or the CIM Object Manager; for example, if the destination handler malfunctions.