[Fiware-ngsi] NGSI binding gap: format of 'reference' and 'providingApplication'

[Rolando Sergio (Guest)]

Hi Tobias,
If I understand well, I fear that your last example is not aligned with your proposal. Probably you meant that the "reference" field should be "http://www.coolContext.org", in order to be notified to the full URL "http://www.coolContext.org/ngsi10<http://www.coolContext.org/ngsi10>/notifyContext".
Similarly, the "providingApplication" field should be (ex.) "http://prov.app.com", if the full URL able to receive the queryContextRequest POST messages is "http://prov.app.com/ngsi10/queryContext"
Is it correct? Otherwise, I would not see any relation between these issues and the upper/lower case choice for mapping NGSI endpoints.

>From our side, in our CAP-CB implementation we assumed that the "providingApplication" field of NGSI-9 ContextRegistration is the URL without the NGSI method, without assuming specific paths (e.g. it could be http://test.app.com/test1, if the provider is able to answer to queryContext POST messages sent to http://test.app.com/test1/queryContext )
The "reference" field in NGSI-10 subscribeContextRequest is instead the full notification URL (e.g. http://www.coolContext.org/ngsi10<http://www.coolContext.org/ngsi10>/notifyContext), and I now see the inconsistency :(

IMHO I'd prefer to leave out only the NGSI method (in the examples above: http://www.coolContext.org/ngsi10<http://www.coolContext.org/ngsi10> and  http://prov.app.com/ngsi10), or even better specifying the full URL (which btw could not be compliant with the NGSI endpoints URL assumption), since it would be more readable in messages, and without problems with casing assumption, also if it is verbose and, I admit, not necessary.

Best regards,
Sergio


From: fiware-ngsi-bounces at lists.fi-ware.org [mailto:fiware-ngsi-bounces at lists.fi-ware.org] On Behalf Of Tobias Jacobs
Sent: giovedì 22 maggio 2014 16.45
To: fiware-ngsi at lists.fi-ware.eu
Subject: [Fiware-ngsi] NGSI binding gap: format of 'reference' and 'providingApplication'

Dear all NGSI-interested people,

in the IoT integration meeting a few weeks ago we identified an underspecified point in the NGSI 9 and NGSI 10 binding, regarding

-          the exact format of the 'providingApplication' field in the NGSI 9 ContextRegistration structure, and

-          the exact format of the 'reference' field in the NGSI 10 'subscribeContextRequest' and the NGSI 9 'subscribeContextAvailabilityRequest' operations.

In order to remove the ambiguity, our proposal is to

-          make mandatory for NGSI9 [ NGSI10 ] servers to provide NGSI9 [ NGSI10 ] functionality under the URL "{serverRoot}/ngsi9"  [ "/{serverRoot}/ngsi10" ]. This deviates from the current binding in that we use lowercase "ngsi" instead of uppercase "NGSI". Using lowercase seems to be more common in REST interfaces, and anyway all IoT GEs have implemented it with lowercase as far as we know.

-          Make mandatory to specify in the 'reference' and 'providingApplication' field only the {serverRoot} part, without the 'ngsi9' part.

o   For example, for announcing in a contextRegistration that context information can be retrieved by sending POST messages to  "http://www.coolContext.org/ngsi10/queryContext" as defined by the NGSI standard, the 'reference' field has to be http://www.coolContext.org/ngsi10<http://www.coolContext.org/ngsi10>.

Please let us know you are ok with that proposal, or if you want to propose an alternative way to remove the ambiguity.

Best regards
Tobias

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