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What is it and why?

The VSS Taxonomy defines what data "entities" (Signals and Attributes) we can deal with, and are used in the protocol(s) defined by W3C Automotive Working group, as well as other initiatives inside and outside the vehicle.

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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 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    For that reason it is required to agree on the definition of schemas and types in a particular usage.  This could might also be derived from this generic analysis.

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• The act of making a measurement (?)

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Data Package:

=   A delivery of data sent at a particular time.

(this means the think of it as the whole Message that is in response to a Request)

Might This will likely need to include some metadata regarding the request:

• Job ID?
• Sequence number (if partial delivery of a Job
• The values container (type Snapshot, Bundle, or single Record)
   

Discussion: What is the general metadata needed when measuring data?

• Vehicle identity – should this be special or is just a measurement on a VSS attribute.  For example VIN number is already defined in VSS.  Presumably it could be just a VSS defined data item?Following the disussions
• Job ID (when applicable)
• Sequence number (if partial delivery of a Job)
• The values container itself (type Snapshot, Bundle, or single Record)

Additional Metadata

Following input given in the W3C data TF:

• Signal metadata
  • Quality
  • Sampling/Compression methods
  • Transmission method
• Usage metadata
  • Data sensitivity
  • Retention time
  • Consent requirements
    

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Record:

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• A format to represent one single measured data value
• Subtypes (Record Types) indicate which Signal has been measured.
• Records are used to represent data with associated metadata.  Different metadata depending on the Record Type, as needed for different cases
• Example of possible record types:
  • Just the value.
  • The value plus a timestamp
  • The value plus a timestamp plus a timestamp accuracy information
  • The value plus additional qualitative information
• All of the above may also specify the signal name, or not:  Some record types may need to specify the signal it is referring to but most do not, because record is delivered in a context where it is known which signal is being measured.

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