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1. Protocol does not (yet) cover all variations of data exchange.
   1.  VISS / W3C Gen2 covers a lot of usage, but supports primarily fetching a single "latest value" measurement, or transferring instant updates according to subscriptions. But the bigger picture should include also exchanging sets of previously measured data between systems.  We can benefit from adding transfer of historically measured data, or derived statistics (e.g. get the average value over time instead of transferring all values), and more.  This work could help protocols like W3C "Gen 2" to cover these bases.
2. Protocol defines only a "transport"
   1. We often discuss protocols that define some mechanisms of data transfer, such as pub/sub semantics, but they are designed to be generic and assume that any type of information can be transferred by the protocol.  Specifically, they do not strictly define the format of the content of the data container (payload).  This makes the protocols widely applicable, but is ultimately not enough without also defining the payload format.  Examples of some such protocols would be MQTT or WAMP
3. Protocol defines transport, query semantics, and some rules for data formats, but are is still too generic.
   1. GraphQL is a generic technology that is complemented by a schema that defines what types of queries can be made and the datatypes that are expected to be returned.   For that reason it is required to agree on the definition of schemas and types in a particular usage.  This might also be derived from this generic analysis.

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