A packet can be represented graphically in the following way:

Speaking of the Plesk XML-RPC packet structure, we distinguish the following parts:
The packet body is structured as follows:
<[operator]>
<[operation]>
<[parameter1]>…</[parameter1]>
...
<[parameter2]>…</[parameter2]>
…
</[operation]>
</[operator]>
This example shows the common structure of the packet body, with one [operator] element and one [operation] element within. In a particular implementation, labels [operator], [operation], [parameter] should be substituted by real operators, operations, and parameters.
Note: There can be many operation sections within one operator. Also, starting from API RPC v. 1.4.0.0, a single packet allows multiple operator elements.
You can look for particular values of labels [operator], [operation], and [parameter] in two places:
Hereinafter, we refer to XML packet header and body together as to a packet.