There is a standard encoding schema which allows for extensions, and permits length- delimited and typecast objects to be constructed.
Objects are length delimited - a 'counted' sequence of octets.
New types of object can be defined out of the 'raw' defined objects. The identifier determines the interpretation of the contents. The contents may itself be a data element or combination of elements defined by context or specification. The size and encoding of each of these 'fields' depends on circumstances as laid out below. This Field is one or more octets in length, and identifies the 'type' of element.