The EMS (``Epos Message Server'') is responsible for sending messages between transactions. There are three classes of messages: Automatically generated messages, User defined messages, and Application generated messages. The most important of these, and the most relevant for this discussion, are the automatic messages.
These will be sent to all involved transactions when a possible or actual conflict situation arises as a consequence of operations against the product stored in the database. ECM commands like check-in and check-out will trigger the EMS, which will then send the required message(s) according to stored rules.
The EMS also provides a user interface for displaying and browsing messages, and replying to them or sending user written messages. The messages themselves are objects which will be inserted into the receiver's sub-database by the message passing operations provided by the EPOSDB .