AW: [RSP-QL] Regarding standalone keyword 'NOW'

For me, NOW was always a bit misleading. Which timepoint does it define exactly?

As you say, "CQELS defines the keyword NOW for windows to include data from the current timestamp": But what defines the current timestamp? In my opinion NOW is only True in an infinitesimal point in time making it useless, if we use your definition. What I mean is that, if you say NOW at t0 (timestamp 0) then at "t1" it is not true/valid anymore.

But maybe I am just misinterpreting the definition of NOW. Generally I would not like to use it, since it seems intransparent to me.

However, and this is taken (and adapted) from Emanuelle's example query at [1], we could use something like [NOW-PT35M]. This means to include every triple between "35min in the past" to "NOW". This makes more sense to me than just using NOW in a window definition, e.g. [NOW].

[1] http://www.w3.org/community/rsp/wiki/Example_of_RSP-QL_query

Best,
Peter

Von: Robin Keskisärkkä [mailto:robin.keskisarkka@liu.se]
Gesendet: Mittwoch, 16. Dezember 2015 10:58
An: public-rsp@w3.org
Betreff: [RSP-QL] Regarding standalone keyword 'NOW'

Hi!
Do we think that the keyword NOW for logical windows will be supported in the RSP-QL specification? I haven't heard it be pushed as a proposal, nor is it any of the sample queries. CQELS defines the keyword NOW for windows to include data from the current timestamp, e.g.:

CONSTRUCT { ?person :in ?room }
WHERE {
   STREAM <http://room.sensor><http://room.sensor%3e> [NOW] {
      ?event a :Observation ;
                   :observedPerson ?person ;
                   :sensorLocation ?room .
   }
}

One possible interpretation of the keyword is that it is syntactic sugar for the minimal range of a logical window in an RSP engine (e.g. an interval limit related to the precision of the engine, or some property set by the user). I'm interested to hear any arguments for keeping the keyword as it is used in CQELS, as opposed to only allowing a window range to be defined as a range (with an optional STEP).

Cheers,
Robin

Best regards,
Robin Keskisärkkä
PhD Student
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