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Common Data Model advanced concepts

Advanced concepts for the Common Data Model (CDM) include the following:

CDM hierarchy

Classes in the CDM are organized into a hierarchy. CDM has a common "base class" and all other classes are extensions of the base class. Moving down the hierarchy leads to more specific classes. This is comparable to the way organizations are structured. A typical example of this could be a manager under which you have several team leaders who in turn have team members under them.

Note

For information about the difference between CDM classes and CIs, see the Overview of the Common Data Model .

A class having underlying classes is called a superclass. The underlying class is called subclass. CDM hierarchy also governs grouping classes that are similar, for example hardware components. The following instance diagram explains the CDM hierarchy with an example:

In the above diagram,

  • BMC_Processor (underlying class) is the subclass and BMC_HardwareSystemComponent  is the  superclass.
  • BMC_Processor represents a CPU in a computer. It defines various attributes that are specific to processors, for example, NumberOfCores. It is grouped together with  BMC_NetworkPortclass, which is similar to BMC_Processor, in terms that both are hardware components. Hence, BMC_Processor and BMC_NetworkPort are grouped under the  BMC_HardwareSystemComponentclass.

  • BMC_SystemComponent is a superclass used to define attributes that are common to all its subclasses. For example, isVirtual indicates that BMC_SystemComponent class is a virtual machine (BMC_Processor  is used to represent the processors of both physical machines and virtual machines. In order to represent it as a virtual machines the isVirtual attribute set to  True). All the underlying subclasses of BMC_SystemComponent inherit the isVirtual attribute.

Attribute inheritance

Because the data model is object oriented, a class can have subclasses that inherit its attributes and the ability to participate in the same relationships. Subclasses are used to further classify a type of CI and give specific attributes to the more granular types. For example, BMC_ComputerSystem has subclasses to represent mainframes, printers, and virtual systems. These subclasses inherit HostName and Domain, and all the other attributes of BMC_ComputerSystem. Inheritance of attributes continues to the end of the tree, so the subclasses also inherit from BMC_System, the class above BMC_ComputerSystem, and from BMC_BaseElement, the base class above BMC_System. An example of attribute inheritance is shown in the following diagram:

Layered model

CDM is structured in layers, wherein the top layer denotes services, middle layer denotes applications, and bottom layer represents servers. The services layer includes business and technical services. The application layer delivers the services in the services layer. The server layer, comprising physical and virtual infrastructure, delivers the application layer. An example of layered model is shown in the below diagram:

 

The following table describes CDM classes corresponding to each layer, along with examples:

Layer

CDM classes

Examples

Business Services

BMC_BusinessService

Home banking, Help Desk, Web sites, E-mail

Technical Services

BMC_BusinessService

Web farms

Applications

BMC_Application, BMC_Database

Custom Banking Application, Sharepoint 2010, Remedy Service Desk, Exchange

Application Systems

BMC_ApplicationSystem, BMC_ApplicationInfrastructure, BMC_ApplicationService

Action Request System, Tomcat Module

Software Servers

BMC_SoftwareServer

Tomcat, Apache webservers, MS SQL Server 2008, LDAP server

Virtual Computers, Compute, Storage and Network Infrastructure

BMC_ComputerSystem

VMs, LPARs

Physical Computers, Compute, Storage and Network Infrastructure

BMC_ComputerSystem

Servers, desktops, laptops, iPads, routers, switches, firewalls, SAN and NAS storage, ESX servers

Subcomponents of Computer Systems

BMC_OperatingSystem, BMC_Product, BMC_IPEndpoint, BMC_LANEndpoint, BMC_HardwareSystemComponents and subclasses BMC_LogicalSystemComponent and subclasses

This structure is not reflected in every model built using the CDM. Some variation is likely depending on a specific scenario. For example, the virtual hardware layer may not exist. Also the number of application layers could vary depending on the complexity of the application being modeled.

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