ion (WS): The WS performs workstation functions (WSF). WSs translate information to a format that can be displayed to the user. 6. Data communication network (DCN): The DCN is the communication net- work within a TMN. The DCN represents OSI layers 1 to 3. It performs data communication functions (DCF). These building blocks generally reflect a one-to-one mapping with function block. However multiple function blocks can be mapped to a single physical block (build- ing block). For example, most legacy network elements (NE) also have a GUI inter- face for technicians to configure and provision the NE. In this scenario a NE in a building block is having OSF and WSF functions in addition to NEF. There are different possible scenarios of multiple function blocks mapping to a single building block and a single function block distributed among multiple building blocks. The possible relations between function and building block are shown in Figure 2.4. Fundamentals of EMS, NMS and OSS/BSS Function blocks Mandatory Optional Optional Optional Optional Not applicable Mandatory Optional Optional Optional Not applicable Not applicable Mandatory Not applicable Not applicable Not applicable Optional Optional Mandatory Optional Not applicable Not applicable Not applicable Not applicable Mandatory Figure 2.4 Relation between function and building blocks. 2.5 Information Architecture This architecture gives an object-oriented approach for TMN. It is based on the management information communications principles defined in the context of the OSI systems management standards. The management view of an object consists of: Attributes: Characteristics of the object Operations: Activities performed upon the object Behavior: Response to operations Notifications: Data emitted by the object Managed object is an abstraction of a physical or logical entity defined for the purpose of managing systems. It contains the attributes and behavior associated with the management of that entity. The design of management systems needs to support modulari