A number of requirements in the spec are expressed in the form of "WebBooks must be XYZ", or "WebBooks should have XYZ". These should all be rephrased in terms of requirements on User Agents, authors, authoring tools, validators etc.
This style of spec writing makes it much clearer what to do in error cases. The most important requirements are those on the User Agent, because that forms the basis of interoperability.
Requirements on authors and authoring tools can also be useful, but given that User Agents need to have normatively defined behavior to handle correct AND incorrect content, expectations on content producers can generally be inferred from the requirements on the User Agent.
Finally, we may care about being able to declare a document as conforming or not to the specification. This too is secondary to defining the behavior of User Agents in terms of interoperability and usability, but it may be helpful in terms of branding and growing the ecosystem. That sort of requirements is better described as "Validators MUST ..." than as "Documents MUST ..."
A number of requirements in the spec are expressed in the form of "WebBooks must be XYZ", or "WebBooks should have XYZ". These should all be rephrased in terms of requirements on User Agents, authors, authoring tools, validators etc.
This style of spec writing makes it much clearer what to do in error cases. The most important requirements are those on the User Agent, because that forms the basis of interoperability.
Requirements on authors and authoring tools can also be useful, but given that User Agents need to have normatively defined behavior to handle correct AND incorrect content, expectations on content producers can generally be inferred from the requirements on the User Agent.
Finally, we may care about being able to declare a document as conforming or not to the specification. This too is secondary to defining the behavior of User Agents in terms of interoperability and usability, but it may be helpful in terms of branding and growing the ecosystem. That sort of requirements is better described as "Validators MUST ..." than as "Documents MUST ..."