[Fiware-data] FI-WARE-data / VisionDocument / Data-Context-Event definition - a proposed revision of the Event definition

[Guy Sharon]

Fano,

I think the discussion you raise brings up the aspect of the semantic 
meaning of an event and the representation of an event.
In the definition of an event in our chapter we discuss the representation 
of an event and not the semantic meaning of an event.
An event may represent change of and attribute value of some entity. It 
can also mean a change in state \ transition.
But how do you communicate the event of an attribute change for example...
You would provide an event which is a specific Data Element that consists 
of Data Element attributes that may include info on the entity for an 
attribute is being changed, the attribute that is being change, the old 
value of the attribute, the new value of the attribute, the time during 
which the change occurred, etc.
Therefore the event representation - how the event is communicated between 
GEs for example is a specific Data Element.
In your example there are 2 types of events - TemperatureMeasured and 
PressureMeasured
TemperatureMeasured consists of tempValue, timeStamp and boilerID 
attributes - for example

I think you refer more to the semantical or ontology level of the event 
which in my opinion is not covered by the whole Data Element discussion.
>From that point based on the example -  we have an event associated with 
temperature of a boiler and another associated with the pressure of the 
boiler - here you treat temperature and pressure as attributes of the 
boiler and events associated to these attributes - which is fine with me - 
but is irrelevant to the above representation.
In other words - event element attributes tempValue, boilerID of the event 
element TemperatureMeasured are semantically mapped to the Boiler.
An event could carry information relevant to more than one entity you wish 
to model which in that case the event does not represent a change in 
attribute but perhaps something more abstract - a situation!
The output of event processing is also an event - a complex event - that 
may not be associable to an attribute or rather is associated to multiple 
attributes of multiple entities.

Regards,
Guy Sharon
Manager
Event-based Middleware & Solutions Group


Event-based Middleware & Solutions

phone : 
+972 4 8296587
mobile : 
+972 54 6976417
address : 
IBM R&D Labs in Israel, Haifa University Campus, Mount Carmel, Haifa, 
31905, Israel
email : 
guysh at il.ibm.com




From:   fano.ramparany at orange.com
To:     boris.moltchanov at telecomitalia.it, 
carlo.licciardi at telecomitalia.it, jhierro at tid.es
Cc:     Fiware-data at lists.fi-ware.eu
Date:   03/01/2012 20:45
Subject:        [Fiware-data] FI-WARE-data / VisionDocument / 
Data-Context-Event      definition - a proposed revision of the Event 
definition
Sent by:        fiware-data-bounces at lists.fi-ware.eu



Hi,
I wish you the best for 2012 and in particular much success to our FIWARE 
project and to the FI PPP program in general!
FT is involved in adding a semantic extension to the Publish/Subscribe GE. 
One step required is to define a ?semantic aware? data schema (*) able to 
capture the Data-Context-Event model that has been defined in the Vision 
Document.
While revisiting this chapter (the overview chapter: 
https://forge.fi-ware.eu/plugins/mediawiki/wiki/fiware/index.php/Data/Context_Management#Overview
), I felt uncomfortable with the definition of an event, which according 
to the current version is ?specific Data Element? with a timestamp to 
represent its date/time occurence.
However, events are generally related to the creation of ?element 
attributes? or changes in the values of ?element attributes? (for example, 
if the temperature of the boiler has been measured 2 times and its 
pressure 1 times. There will be 3 events, each of them will correspond to 
a Context Element attribute. More precisely, 2 context attributes for the 
two temperature measurements and 1 context attribute for the pressure 
measurements. The timestamps of those 3 measurements would probably be all 
different because the measurements would be done at different times. The 
?element attribute? corresponding to the 2nd temperature measurement will 
supercede the one corresponding to the 1rst temperature measurement. 
(Note: with the approach proposed in the working document I refer to below 
(**), the timestamp is a meta-data associated to the ?element attribute?).
For this reason I?d like to propose a slight revision of the event 
definition and state that ?an event is a specific Data Element attribute? 
(with a mandatory timestamp meta data to capture its date/time 
occurrence). This definition would replace this one: ?an event is a 
specific Data Element?.
Any comment/feedback on this and on the working document which proposes a 
flexible ontology which aligns with our data model, is more than welcome,
Best regards,
Fano
(* called an Ontology in the semantic web framework)
(** This document proposes an Ontology for Defining Ontologies for the Pu 
ReleaseV0. In case the link doesn?t work, the document is in 
FI-WARE->files->OntologyV0.pdf on the FI-WARE fusion forge web site)
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