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

In general I share the concerns of Peter. We introduced NOW in [1] to
enable the possiblity to declare windows in the past, e.g., a window in the
interval (NOW-24H,NOW-23H].

If we are planning to use NOW in other situations (i.e., not in the context
of a window definition), can you point out the use case on where it is
needed?

Regards,

Daniele

Il giorno mer 16 dic 2015 alle ore 13:14 Wetz Peter <peter.wetz@tuwien.ac.at>
ha scritto:

> 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> [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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