Figure 4: Structure and relations of the module MESSAGE
Messages are used for the communication between components on the same TNC communication layer. These messages and their format are specified by so called bindings for the interfaces IF-M, IF-TNCCS and IF-T. The module MESSAGE depicted in Fig. 4 contains an object-oriented implementation of the various messages specified by the currently supported bindings (cf. section 1). Therefor, every message consists of a message header (Header) and a message content value (Value). The modules IM, TNCCS and TRANSPORT use the module to encode object-oriented messages for the transmission and decode messages into their object-oriented representation after reception. For this purpose, the module provides so called writers, which are used to encode a message into its format for transmission as defined by the TNC-WG as well as so called readers, which are used to decode a message after reception in its object-oriented representation for further processing. Furthermore, the modules IM, TNCCS and TRANSPORT can use Message Factories provided by the module MESSAGE, which aid in the creation of a new message. To control the creation of messages (e.g. when a message is created with a factory or a message is decoded by a reader), the module does contain so called Message Builder. A Message Builder validates the parameters, which are used for the creation of an object-oriented message against rules specified by the Validation part. A builder creates and returns a message only if all parameters are satisfying. A message is immutable after its creation.