MDS4 includes two WSRF-based services: an Index Service, which collects data from various sources and provides a query/subscription interface to that data, and a Trigger Service, which collects data from various sources and can be configured to take action based on that data. An Archive Service, which will provide access to historic data, is planned for a future release.

The Index Service is a registry similar to UDDI, but much more flexible. Indexes collect information and publish that information as resource properties. Clients use the standard WSRF resource property query and subscription/notification interfaces to retrieve information from an Index. Indexes can register to each other in a hierarchical fashion in order to aggregate data at several levels. Indexes are “self-cleaning”; each Index entry has a lifetime and will be removed from the Index if it is not refreshed before it expires.

Each Globus container that has MDS4 installed will automatically have a default Index Service instance. By default, any GRAM, RFT, or CAS service running in that container will register itself to the container’s default Index Service.

The Trigger Service collects information and compares that data against a set of conditions defined in a configuration file. When a condition is met, or triggered, an action takes place, such as emailing a system administrator when the disk space on a server reaches a threshold.