[Fiware-ngsi] one further binding question

[Moltchanov Boris]

Good point here! I'm saying it differently then, the type+entityID shall be unique.
This answer here is defined by a mathematic logic :):
1. if in the NGSI spec the type is a mandatory field, then you may say that the uniqueness is guaranteed by the couple of type+entityID, then the entity ID itself could be not unique, and within different types entityID could have the same values. However entityID must be unique for the same type. This is also guaranteed by the fact that a data structure with missing type will invalidate entire structure;
2. if the spec defines the type as an optional field then the entityID must be unique, at all.

I don't remember now what is defined in the specification about this, however personally I opt for the first solution where type is mandatory and type+entityID is unique as well as:

a.       universal uniqueness of only entityID is almost impossible (it shall be a sort of a strong world recognized and world applied standard like with MAC addressing;

b.      many application domains, e.g. boris as a passport name and social network name could use the same naming and conversion for purpose from the application domain names to something unique is very onerous and will impact on performance.

Currently Pub/Sub GE based on the contest broker considers type+entityID as unique, while entityID could be the same in different domains (types). If the type is missing in the context request it is considered by default as a personal name.

BR,
B

From: fiware-ngsi-bounces at lists.fi-ware.eu [mailto:fiware-ngsi-bounces at lists.fi-ware.eu] On Behalf Of Bisztray, Denes (NSN - HU/Budapest)
Sent: Thursday, March 29, 2012 2:04 PM
To: ext Tobias Jacobs; fiware-ngsi at lists.fi-ware.eu
Subject: Re: [Fiware-ngsi] one further binding question

Hi Tobias,

There is that "if". I would go for the variant "EntityID uniqueness is guaranteed by the ID alone."

Best,
Dénes

From: ext Tobias Jacobs [mailto:Tobias.Jacobs at neclab.eu]
Sent: Thursday, March 29, 2012 1:16 PM
To: Bisztray, Denes (NSN - HU/Budapest); fiware-ngsi at lists.fi-ware.eu
Subject: RE: [Fiware-ngsi] one further binding question

Hi Denes,

In Table 5.5.5 in the NGSI specs it is written "If EntityId uniqueness is only guaranteed in combination with Type, then Type SHALL be present."
I interpret this as NGSI admitting to have several Entities having the same name but different type.

Such sets on Entities with the same name would be represented by the same ../contextEntities/{entityID} resource in our binding (unless we agree to do it differently).

Best
Tobias

From: Bisztray, Denes (NSN - HU/Budapest) [mailto:denes.bisztray at nsn.com]
Sent: Donnerstag, 29. März 2012 10:09
To: Tobias Jacobs; fiware-ngsi at lists.fi-ware.eu<mailto:fiware-ngsi at lists.fi-ware.eu>
Subject: RE: [Fiware-ngsi] one further binding question

Something completely different:
I assumed until now that the Name of the EntityId  in our system has to be unique because of the nature of the RESTful binding. Does that hold?

Best,
Dénes

From: fiware-ngsi-bounces at lists.fi-ware.eu<mailto:fiware-ngsi-bounces at lists.fi-ware.eu> [mailto:fiware-ngsi-bounces at lists.fi-ware.eu]<mailto:[mailto:fiware-ngsi-bounces at lists.fi-ware.eu]> On Behalf Of ext Tobias Jacobs
Sent: Wednesday, March 28, 2012 5:51 PM
To: fiware-ngsi at lists.fi-ware.eu<mailto:fiware-ngsi at lists.fi-ware.eu>
Subject: [Fiware-ngsi] one further binding question

Dear members of the NGSI list,

The binding of NGSI-10 is now as good as finished, see the current version at
https://forge.fi-ware.eu/scmrepos/svn/iot/trunk/documents/Ngsi10-RestfulBinding-Draft.docx

Unfortunately, I have identified another issue I like to discuss with you. Please let me know your opinion.

We previously agreed that a GET on an ../{EntityID} resource results in a list of all available attribute values in only one ContextElement, without attribute domains. We further agreed that a GET on ../{EntityID}/attributeDomains results in the same information, but here the response consists of one ContextElement per attribute domain.

Now here is the problem I see: The possibility to distinguish between these two kind of queries goes beyond the specification of NGSI-10. NGSI-10 only allows a query for all attributes of an entity, and how the returned information is structured is not written in the standard.

My proposal to resolve this is to disallow the GET on ../{EntityID}/attributeDomains, which would mean that this resource becomes one which does not allow any interaction. Additionally, we could leave it to the system if the attributes should be structured by domain or not, like the NGSI-10 spec does.
Martin does not agree with that, his proposal is to accept this slight extension of NGSI-10.

What speaks for Martin is (correct me if I cite you incorrectly, Martin)

-          Allowing a GET on ../{EntityID}/attributeDomains is natural, and users would expect it

-          The functionality is useful
What speaks for my approach is

-          A gap between the functionality of the binding and the functionality of NGSI-spec might cause unforeseen problems, for example when someone has already designed a system according to the NGSI-specs and now wants to put a REST interface on top.

Thanks in advance for letting us know your opinion.
Best
Tobias

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