2.5 Synchronization and Serialization Issues

On one hand we mean by ‘synchronization’ the ability of a client to read or write values and attributes in a single transaction. For example, most applications want to ensure that value, unit, and limits of a particular measuring channel are in ‘sync’. This is ensured in FDT via XML documents for data transfer. All elements of a document are transferred within a single transaction.

In general, DTMs should try to preserve synchronization of data items and attributes that are read or written in a single operation. Synchronization of items read or written individually in separate operations is not required.

On the other hand we mean by ‘synchronization’ the additional handshaking between the Frame Application and the DTMs to signal such states as ‘ready’ and ‘parameter changed’. This handshaking is especially necessary within a multi-user environment to synchronize DTMs among each other and with the Frame Application according to the current application context. Each DTM has to take some simple rules into account to assure that the Frame Application can do this synchronization. Many of these issues will be clarified in the detailed descriptions of the methods and the according sequence charts below.