The protocol is based on segments, a segment identifies a specific action which is meant to be performed. Every segment is composed by two messages: a request and a response. Every message is made up of two parts:

• the first one is the heading
• the second one is the actual message to be sent.

Those two parts are encapsulated in an envelope.

The envelope is declared by the envelope tag while the heding is declared with the header tag, as shown by the following example:

<?xml version="1.0" encoding="UTF-8"?>
<envelope>
    <header>
        <actor>test</actor>
        <user>test</user>
        <password>test</password>
        <version>1.0.0</version>
        <timestamp>20210424170000</timestamp>
    </header>
    <!-- REQUEST MESSAGE -->
</envelope>

The heading is composed by five fields:

• the client identifier in the system (actor)
• the user identifier (user)
• her password
• the protocol version used (version)
• the timestamp.

• In response messages the heading is a bit different since it does not contain actor, user and password:

<?xml version="1.0" encoding="UTF-8"?>
<envelope>
    <header>
        <version>1.0.0</version>
        <timestamp>20030424170000</timestamp>
    </header>
    <!-- RESPONSE MESSAGE -->
</envelope>