ch com- municates with the TMN for the purpose of being monitored and/or controlled. The NETWORK MANAGEMENT T0412990-99 Network Element Function Operation Systems Function Transformation Function Workstation Function The TMN functional boundary Figure 21.14 TMN function blocks. NEF provides the telecommunications and support functions which are required by the telecommunications network being managed. The NEF includes the telecommunications functions that are the subject of manage- ment. These functions are not part of the TMN but are represented to the TMN by the NEF. The part of the NEF that provides this representation in support of the TMN is part of the TMN itself, while the telecommunication functions themselves are outside. Workstation Function (WSF) Block. The WSF provides the means to interpret TMN information for the human user, and vice versa. The responsibility of the WSF is to translate between a TMN reference point and a non-TMN reference point, and hence a portion of this function block is shown outside the TMN boundary. Transformation Function (TF) Block. The transformation function block (TF) provides functionality to connect two functional entities with incompatible communication mech- anisms. Such mechanisms may be protocols or information models or both. The TF may be used anywhere within a TMN or anywhere at the boundary of a TMN. When used within a TMN, the TF connects two function blocks, each of which supports a standardized, but different, communication mechanism. When used at a boundary of a TMN, the TF may be used as communication either between two TMNs or between a TMN and a non-TMN environment. When used at a boundary at two TMNs, the TF connects two function blocks, one in each TMN, each of which supports a standardized, but different, communication mechanism. When the TF is used between a TMN and a non-TMN environment, the TF con- nects a function block with a standardized communication mechanism in a TMN to a functional entity with a nonstandardized communication mechanism in the 