While not all Activity Streams 2.0 implementations are expected to implement support for the Extended properties, all implementations MUST at least be capable of serializing and deserializing the Extended properties in accordance with the Activity Streams 2.0 Core Syntax.
This is not a requirement of the vocabulary. The vocabulary can be used with any syntax or serialization. The quoted text actually describes a requirement of AS2-Core, not AS2-Vocab.
This is not a requirement of the vocabulary. The vocabulary can be used with any syntax or serialization. The quoted text actually describes a requirement of AS2-Core, not AS2-Vocab.