See also: IRC log
<scribe> Meeting: SDW coverages
<phila> issue-1?
<trackbot> issue-1 -- Blah blah test -- closed
<trackbot> http://www.w3.org/2015/spatial/track/issues/1
<scribe> scribe: kerry
<scribe> scribeNick: Kerry
<billroberts> https://www.w3.org/2016/03/09-sdwcov-minutes
<phila> PROPOSED: Accept last week's minutes
<billroberts> +1
<jtandy> +1
<eparsons> +0 Not there
Proposed: accept last weeks minutes https://www.w3.org/2016/03/09-sdwcov-minutes
+1
<phila> +1
RESOLUTION: Accept last week's minutes
<billroberts> https://www.w3.org/2015/spatial/wiki/Patent_Call
<billroberts> https://www.w3.org/2015/spatial/wiki/Meetings:Coverage-Telecon20160323
<billroberts> https://www.w3.org/2015/spatial/wiki/Coverage_UCR_notes
billroberts: at bottom in summary
see that subsetting came out a lot
... assign an identifier to a subset of a coverage of a
dataset
... also for provenance so you can point to how the processing
happened
... the question of delivering a full coverage is a special
case of delivering a subset -- if we address addressing and
formatting it will be solved
... also some use cases for poihnt cloud and time series --
need to keep these in mind
... also note that the region of interest might be complicated,
not just a bounding box, may be polygon or tunnel
underground
... any comments?
jtandy: they are the things I can recall
phila: note the way subsetting
tumbles out becuase we are struggling in dwbp to say something
that is *not* spatailly-specific
... dwbp does not have good use cases for this
billroberts: also we have time subsets and variable subsets
+q
<Zakim> jtandy, you wanted to query predefined subsets or on-the-fly query
<eparsons> jtandy
jtandy: we had a long email
thread on subsetting for BP
... one kind is subsetting for useful chunks to be manageable
(a predefined set)
... other kind is an on-the-fly query chunk
... we need both
... rdf datacube does predefined type but not query type
billroberts: datacube can be used for query-type but perhaps less flexible
jtandy: when i assign an
identifier to a subset it could be anythinh
... but a query type identifier is also an api, effectively
<phila> kerry: I hate us calling it subsetting given all the different dimensions that we need to talk about
kerry: does not like "subsetting"
<phila> Discussion between phila and kerry about whether audience for Coverages doc is only spatial folks
<phila> kerry: How about 'sub coverage?'
<phila> billroberts: That makes sense to me
<phila> phila: Doesn't like 'sub coverage'
<scribe> ACTION: kerry to present some suggestions for renaming "subsetting" [recorded in http://www.w3.org/2016/03/23-sdwcov-minutes.html#action01]
<trackbot> Created ACTION-152 - Present some suggestions for renaming "subsetting" [on Kerry Taylor - due 2016-03-30].
<BernadetteLoscio> yes!
<billroberts> http://w3c.github.io/dwbp/bp.html#EnableDataSubsetting
BernadetteLoscio: we have a
proposal as in the irc, but it is difficult to test
... it is generic and important but there are different
approaches
... e.g. apis, queries
... we are not sure whether we should have this as a bp or to
just describe it
... what would be helpful to you and how would it be
testable?
<Zakim> jtandy, you wanted to ask if you could cover 'subsetting' as an example operation in your API
jtandy: when I look at subsetting
I think it is one example of the way you could work with
data... there are other BP about offering an API in DWBP
... data subsetting makes a lot of sesne for slices for
statistical, etc, but when I look more generically it is really
just an operation you provie thru an API
... could be just an illustrative example
... but it makes a lot of sense for time series and satellite
data (somehow differently)
bernadette: : should we also talk about subsetting for download
jtandy: you should also talk
about the data you take away after downloading
... I would suggest when working with large datasets a typical
use case would be an api to select parts of that dataset
... difficult for you to reference what we do, but I suggest
just describe an illustrative example of a convenience API
BernadetteLoscio: perhaps we can talk about subsetting along with downloads as another example
billroberts: the problem with
api/query is that it is futile to specify upfront what it
should look like in general
... maybe all we can do is say "you need an API" or esle we end
up inventing yet another query language
... needs to be up to the data provider
jtandy: agrees
phila: <moved us with his absent speech>
<phila> phila: Requirement no. 1 can assign an identifier to a subset of a coverage dataset
phila: we have been saying "you
just give it a uri", although a uri *is* an api
... for bulk download is it useful to say you can use the api
and you can give it an example of its own, e.g. meteorological
data for the last week
... should this go in dwbp or sdw?
... should dwbp do this ... your first ucr says you need to
asign an identifier to a subset
billroberts: yes it would be useful
jtandy: it makes sense to for
dwbp to provide some advice -- if you have data that is too big
for a web application then providew a mechanism to get hold of
bits of it
... eg. using predefined slices or an API
... test by "here is a massive dataset -- can you work with it
in a browser app?
billroberts: use cases where this emerged was wanting to attach some metadata to it, something that is the full set, not a subset
<phila> is that helpful newton_dwbp?
<newton_dwbp> I liked jtandy point
billroberts: need to look again at email thread on this, any otehr comments?
BernadetteLoscio: we like jtandy's idea and will bring to our dwbp discussion. thank you very much
billroberts: which aspects of rdf datacube would be good for defining subsets?
<Zakim> jtandy, you wanted to note qb:slice
billroberts: bill will write note on pros and con of datacube and mechanisms that would be helpful for subsets
dmitrybrizhinev: ... we are a
group of students working on an example implementation for
coverages, we are worried about verbosity of datacube
... flipside is taking a subset with lots of granularity with a
sparql query is useful butused verbose
... i have been converting the coveragesjson to rdf but this is
the query... is there a best of both worlds
billroberts: please share anything written up
jtandy: agree about way too verbose, jonblower keeps saying this cannot be used to carry the data, but the metadata might be useful
<jtandy> https://www.w3.org/TR/vocab-data-cube/#slices
jtandy: for describing subsets
there is qp:slice and also a mechanism for creating arbitrary
groups in the spec
... leaving the data in a desne array is arguable no different
to the way we deal with goespatail stuff all the time, eg
geometry objeects in WKT or in GML
... becuase we want to treat the whole geometry as an object
(we don't break it up), the same can apply to a dense array of
data
... in the same way the geosparql can provide operations on
data, when we are working with coverage data in a webby form we
ned to provide some additional mechanism for querying
inside
billroberts: e.g.75th point of
array needs to be accessible, and you need some coordinates
that stick with the points... that kind of conciseness is
needed for whole grid but when there are only bits it may work
well
... datacube couldwork well itself for a small subset if not
the entire grid
jtandy: if you just want ith column and jth row ...
<phila> kerry: were you suggesting, Bill, that the QB model could be used as a response format for a query over a bigger set
<phila> billroberts: Not precisely, but that structure of an observation
<phila> ... If you just have one data point, you need all the dimensional info and the metadata. Some metadata applies to the whole dataset, some to a specific point.
<phila> ... If you have a grid, you don't need all the coords 'cos you can work them out but a point cloud does need them.
billroberts: the structure of an observation is very useful for datacube way
jtandy: index space querying , natural coord subsetting, more work to do here...
phila: what proportion of
coverage data is on a regular grid?
... I am thinking of those with only 2 or 3 lines with regular
definition and you can work the rest out
... in such cases a template uri could be generated that does
identifiy a "slice"
... so we could say "of you have a regular grid pattern this is
how you generate the uri template"
<Zakim> jtandy, you wanted to respond to phila's question about regular grids
jtandy: yes it is a large
fraction by volume and number of datasets, eg satellite
imagery,
... but there are other important cases such as in-situ
observations by radiospondes or buoys or gliders irregular
coverages happen more (like opendap/netcdf index-based
subsetting)
eparsons: aggrees. my meta-question is , where is the stuff with a more semantic approach -- are we just reinventing the wheel of tools in other places?
jtandy: phil had said data is
easy, metadata is challenge. the metadata is the bit to get the
advantage of linked data such as what you are measuring
etc
... metadata as linked data is key, then something else for
dense arrays of data
eparsons: so lets not get worked up on data size then as ther are other approaches
billroberts: index array of data is good approah for some stuff, but we need to think harder about others
billroberts: jeremy stole out
timeslot
... we had been proposing to follow the main group for time
changes
kerry: kick them off!
s/Jermey/Jeremy/
<phila> May I suggest a Doodle poll?
billroberts: moans about "the australian issue"
+1 to bill's idea
<phila> 16:00 CEST, 15:00 BST etc.
billroberts: meeting close
<billroberts> bye everyone