[Fiware-ngsi] Interpretation of DELETE on http://{serverRoot}/{apiVersion}/contextEntities/{entityID}

[Juanjo Hierro]

Hi,

  I believe that "creation"/"deletion" of entities is nothing that actually fits very well with the NGSI model.

  You don't create or delete entities.   Existence of a given entity is something you get aware of the first time someone submits an NGSI request that refers to that entity (e.g., an updateContext, registerContext, etc)

  IMHO, invoking the delete request should mean that all context information available about the referred entity is deleted (actually forgotten).   But this doesn't mean that a new request may arrive that again refers to the entity which should be handled like the first time a request on an entity that we were not aware of before, is received.   This should indeed easy implementation of a ContextBroker, because otherwise you should keep track of "deleted" entities.  Otherwise, you wouldn't be able to trigger error responses to requests on entities you have "deleted" some time ago.   I believe this introduces unnecessary complexity to an implementation of the ContextBroker, with no particular added-value.   It should be rather much simpler to just delete all context information about the entity.   If someone then issues a NGSI request that refers to that entity afterwards, that should not be a problem.  You would just handle it as if it were a request on an entity you were not aware of.

  My two cents,

-- Juanjo

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On 02/04/14 18:11, Rolando Sergio (Guest) wrote:
Hi Fermin,
I completely agree with Tobias, that API simply deletes every context attributes related to the specified entityID.
NGSI entities do not "exist" in any way, and therefore are not created nor destroyed.

Best regards,
Sergio

________________________________
From: fiware-ngsi-bounces at lists.fi-ware.org<mailto:fiware-ngsi-bounces at lists.fi-ware.org> [mailto:fiware-ngsi-bounces at lists.fi-ware.org] On Behalf Of Tobias Jacobs
Sent: mercoledì 2 aprile 2014 17.06
To: Fermín Galán Márquez; fiware-ngsi at lists.fi-ware.eu<mailto:fiware-ngsi at lists.fi-ware.eu>
Subject: Re: [Fiware-ngsi] Interpretation of DELETE on http://{serverRoot}/{apiVersion}/contextEntities/{entityID}

Hi Fermin,

In NGSI there is not really the concept of adding or removing an entity, one can only add or remove attribute values for entities.

Probably for an NGSI-based database it makes sense to remove the record for an entity about which no attribute value is available anymore, but this is more a design choice for the implementation than a matter of the standard.

Best
Tobias

From: fiware-ngsi-bounces at lists.fi-ware.org<mailto:fiware-ngsi-bounces at lists.fi-ware.org> [mailto:fiware-ngsi-bounces at lists.fi-ware.org] On Behalf Of Fermín Galán Márquez
Sent: Mittwoch, 2. April 2014 16:56
To: fiware-ngsi at lists.fi-ware.eu<mailto:fiware-ngsi at lists.fi-ware.eu>
Subject: [Fiware-ngsi] Interpretation of DELETE on http://{serverRoot}/{apiVersion}/contextEntities/{entityID}

Current NGSI10 binding document version 1.0 at http://forge.fi-ware.org/plugins/mediawiki/wiki/fiware/index.php/FI-WARE_NGSI:_publicly_available_documents states:

3.1.4 DELETE [on http://{serverRoot}/{apiVersion}/contextEntities/{entityID}]

This operation allows deleting all information about the Context Entity represented by the resource, i.e., all related attribute
values and metadata. The request does not have a body, and the response body is an instance of StatusCode.

Our interpretation of this (and our implementation in Orion Context Broker, aligned with that interpretation) is that removing all related attributes and metadata of an entity is equal to delete the entity itself.

We would like to know how other NGSI implementors are interpreting this. Are your implementing this in a similar way?

Thanks for the feedback!

Best regards,

------
Fermín
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