The structure of the JMS 1.1 specification reflected the domain-specific APIs introduced in JMS 1.0, with section titles such as "QueueConnection" and "TopicSubscriber". This was an inappropriate structure even in JMS 1.1 since these interfaces had been superseded in JMS 1.1 by the "unified" API. The addition of the simplified API in JMS 2.0 makes that structure even more inappropriate.
The JMS 2.0 specification has now been completely restructured along functional lines, with chapter headings such as "connecting to a JMS provider" and "receiving messages". These describe each area of functionality in generic terms followed by a description of how it is implemented in the various APIs. In general these chapters contain the same text as in the previous version.
In particular a new section 2.5. "JMS APIs" introduces the various APIs introduced in each version of JMS. A new section 2.7. "Classic API interfaces" contains a diagram of the objects used in the "classic" (formerly "standard") API, and section 2.8. "Simplified API interfaces" contains a diagram of the objects used in the simplified API.