| The Representation Protocol also defines a set of Static Conformance Requirements (SCR) tables. These tables define what a product is required to support. The tables also indicate optional commands or Elements. Here is an example from the SCR tables: Command | Support of Synchronization Server | Support of Synchronization Client | | | Sending | Receiving | Sending | Receiving | Chal | MUST | MUST | MAY | MUST |
This example is from the Common Use Elements section of the SCR tables. For a Server, the Chal command is required for sending and receiving. However, for a Client, it is only required to receive the Chal command. According to the RFC 2119, MAY indicates entirely optional, SHOULD indicates strongly suggested (i.e. a good technical reason for not implementing), and MUST indicates required. |