This section generally describes version 2.7 (final) of the standard models prepared by the DMTF. Where there have been major changes between version 2.7 and 2.8 (in particular, in the User Common Model) I have tried to use the 2.8 classes even though they were not firm at the time of writing. Although these models will be changed, backwards compatibility will be guaranteed for all 2.x releases. You should, however, check any references I make here against the most recent version of the models.
The DMTF has co-ordinated the preparation of various models  which can be divided into three categories: a Meta-Model , a Core Model and numerous Common Models.
In addition to these three DMTF-produced models, it is expected that individual companies will extend these models to encompass features unique to their products. These models are known as extension schema and they are created by subclassing from the Core and Common models.
The Meta-Model describes the components which can be used to build models (e.g., an Indication is a Class which is a NamedElement. A Method is a NamedElement and a Class aggregates a number of Methods.). Although this meta-model has great theoretical significance, it does not help you build a model of a particular system and I will not consider it further.
The Core Model which contains concepts applicable to the management of anything from my toaster to the largest telecommunications network.
You can think of the Core Model as the basic tree on which all other models are hung ”it contains a relatively small set of classes, associations and properties giving a basic vocabulary for describing managed systems.
It is not anticipated that the Core Model will ever undergo substantial change because it is very generic and many Common Models (see below) have already been written which rely on it. I give more information about the Core Model on page 90.
The Common Models which are listed in Table 3.1. These describe the management structure of a number of particular applications: storage, networking, desktop computing, etc. I explain a few of these starting on page 98.
 Freely available from the DMTF Web site.