Introduction

This capability describes the messaging capability. The two purposes of messaging are firstly to provide meta-data about a PLCS exchange and secondly to enable recording of an audit trail relating information to its transfer between PLCS systems. It covers two functions: Envelope provides the audit trail of transmission, while Message describes the data transmitted and the reasons for sending the information.

The way Messaging provides an audit trail can be described by analogy with an e-mail service. The Envelope corresponds to the e-mail header, the Message purpose to the text of the e-mail, and each Message Content_item to an attachment, which in this case contains the information to be loaded into a PLCS system.

Each transmission contains a single Message and one or more DEX data sets (that is, instances of the data specified by a PLCS DEX). The Message is classified to identify the AP 239 schema version and the DEX and its version. It may also be classified to show the purpose of the transmission, such as initial load or incremental update.