1 The prototype annotation

The main construct to specify the type and structure of homogenous data is a MP_Prototype annotation. It may be attached to an operator and its value (which is again a MP Tree, often referred to as prototype tree) specifies the syntax, and, possibly some semantics, of all arguments of the operator. Subsequently, the entire collection of argument data items can be placed in a data packet. A receiver side would retrieve the prototype and use it to properly decode the (headerless) data.

For describing prototype trees, we more formally define the syntax of a prototype annotation by

<Prototype AP> ::= AP(MP_Prototype)<MP TypeSpec>
 
<MP TypeSpec> ::=  <Basic TypeSpec>|
    <Operator TypeSpec> 

where AP(x) is an Annotation Packet of type x,. Furthermore, we make a distinction between prototype specification time, the time at which we create (send) the prototype, and data communication time, the time at which we actually send the data described by the prototype.