To provide means for the description of management information has always been an important part of the definition of management architectures. Syntax and semantics of information descriptions are defined in the so called information model; the access to it in the communication model. The focus of management information traditionally lay on attributes and properties of single objects. Although, e.g. the ISO/OSI (Open Systems Interconnection, [#!iso10165-X!#]) management architecture already defined a General Relationship Model (GRM, [#!iso10165-7!#]), it was never widely used in IT-management. Only in recent years the issue regained more interest [#!rodr00!#]--mainly with the increasing number and complexity of the inter-service, -system and -domain dependencies.
Examples for typical information specific to single managed objects are variables of the Management Information Bases (MIBs, [#!rfc1213!#]) defined in the Internet Management Architecture, like ...mib-2.system.sysLocation that is defined to store the system's location. This kind of information is either stored at the real objects (hardware components, applications, etc.) and accessible via management agents using standardized protocols or within the corresponding object representation at the management tools.
The following subsections focus on another type of management information which has gained more and more importance with the growing complexity of IT-systems and networks: the dependencies between managed objects, captured by the so called Dependency Models In the following, various types of such models are illustrated together with their applications. Although most model types could also be used for the management of lower (communication) layers, they are analysed with regard to service dependencies. I.e., we leave aside models at the lower OSI layers, like network topologies. Of course, knowledge about the underlying communication structures is also essential e.g., to diagnose problems or to identify bottlenecks, but this has to be (and to a satisfactory part already is) carried out by very different techniques than the ones needed on the level of end user- and supplementary services, with a much higher degree of complexity and dynamics.