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12:58:30 <trackbot> RRSAgent, make logs world
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12:58:32 <trackbot> Zakim, this will be SDW
12:58:32 <Zakim> ok, trackbot
12:58:33 <trackbot> Meeting: Spatial Data on the Web Working Group Teleconference
12:58:33 <trackbot> Date: 15 June 2016
12:59:32 <billroberts> hi everyone - I think it will be a small meeting today - lots of apologies.  But will give people a few minutes to join the webex
12:59:51 <billroberts> regrets+ kerry
12:59:56 <billroberts> regrets+ jtandy
13:00:02 <billroberts> regrets+ scottsimmons
13:00:24 <billroberts> regrets+ edparsons
13:00:28 <Maik> present+ Maik
13:01:05 <billroberts> Rob probably joining by IRC only, Jon might join for second half
13:02:04 <Duo> present+ Duo
13:02:35 <billroberts> scribe: maik
13:03:37 <billroberts> Proposed: approve minutes of last meeting https://www.w3.org/2016/06/01-sdwcov-minutes
13:03:47 <billroberts> +1
13:03:55 <Duo> +1
13:03:56 <Maik> +1
13:04:06 <billroberts> Resolution: minutes approved
13:04:27 <billroberts> https://www.w3.org/2015/spatial/wiki/Patent_Call
13:04:51 <billroberts> https://www.w3.org/2015/spatial/wiki/Meetings:Coverage-Telecon20160615
13:05:23 <billroberts> https://www.w3.org/2015/spatial/track/issues/18
13:05:45 <billroberts> requirement for 'model reuse' dropped
13:05:57 <billroberts> https://www.w3.org/2015/spatial/track/issues/19
13:06:19 <billroberts> agreement on issue 19 that the requirement is "to be able identify what type of coverage is being encoded "
13:07:20 <Maik> billroberts: week before: how specific our solution should be
13:07:26 <Maik> ... grids most important
13:07:30 <Maik> ... but also time series
13:07:42 <Maik> ... and flexible for more arbitrary domains
13:08:19 <Maik> ... covers 3 concerns: subset spec, where metadata does, encoding
13:08:57 <Maik> Duo: updates
13:09:15 <Maik> ... switch from previous dataset (set of geotiff tiles)
13:09:39 <Maik> ... to dggs (discrete global grid system)
13:09:53 <Maik> ... recursive resolutions (pyramid)
13:10:36 <Maik> ... our solution: pointcloud-type, all observations independent, no topology, but there are tiles which have an order between each other
13:10:51 <Maik> ... added graphs for timeseries
13:11:04 <Maik> ... not published yet, but in a few days
13:11:18 <Maik> billroberts: how are range values encoded?
13:11:31 <Maik> Duo: two types of values
13:12:12 <Maik> ... a) aggregate value, b) "zoomed" in
13:12:24 <Maik> ... essentially: an image
13:13:09 <Maik> billroberts: geotiff as base64 encoded string, still like that?
13:13:12 <Maik> Duo: yes
13:13:49 <billroberts> Maik: how are you encoding timeseries?
13:14:19 <billroberts> Duo: it's a timeseries of the single aggregated value per area/locatinon
13:14:32 <billroberts> Duo: it displays a plot of the aggregate values
13:14:59 <billroberts> scribe:billroberts
13:15:30 <billroberts> Maik: finished specifying and implementing tiling of ranges based on the index space
13:15:38 <Maik> http://reading-escience-centre.github.io/covjson-playground/
13:15:48 <Maik> examples -> Grid (tiled)
13:16:38 <billroberts> ...allow data to be stored not just in one tiled pattern, but possibly several different tiles, sliced in different ways
13:17:06 <billroberts> ...eg tiled according to a bounding box and you get a time series of tiles of bounding boxes
13:17:22 <billroberts> ...this allows generating static tiles that can be hosted cheaply
13:18:16 <billroberts> ...a 'TiledNdArray' is a very generic data structure, not really tied to coverages
13:18:36 <billroberts> ...it's not coordinates, it's just array indices
13:18:54 <billroberts> ...that's probably the last major new feature to go  n CoverageJSON before end of Melodies project
13:19:02 <billroberts> scribe:maik
13:19:38 <Maik> billroberts: scope of spec
13:19:48 <Maik> ... about 1 year to finish everything
13:20:15 <Maik> ... need to demonstrate some progress, a draft that can be reviewed and refined
13:20:30 <Maik> ... first public working draft soon after mid of Sep
13:21:11 <Maik> ... Maik, Jon, I will get tomorrow next month to start the process of writing the spec
13:21:48 <Maik> ... main components, how they relate to each other
13:22:03 <Maik> ... main part: how each part is specified
13:22:21 <Maik> ... JSON vs RDF vs mix, metadata vs data values ...
13:22:28 <Maik> ... using existing vocabs where we can
13:22:45 <Maik> ... have to make sure things are linkable (SDW req)
13:23:03 <Maik> ... parallels between two approaches
13:23:34 <Maik> ... handling of ranges, domain (though there are parallels)
13:23:46 <Maik> ... rdf data cube: domain info for each data point
13:24:04 <Maik> ... covjson: compact domain definition, not repeated for each point if possible
13:24:20 <Maik> ... (for grids most efficient)
13:24:52 <Maik> ... to what extend can JSON-LD help join the two views together, at least for domain, not really ranges
13:26:38 <billroberts> Maik:  even for the domain, we hit restrictions of JSON-LD 1.0 because it doesn't allow idiomatic JSON structures
13:26:49 <billroberts> ...so sometimes want to step away from JSON-LD
13:27:09 <billroberts> ...but it works quite well for describing CRS, measured properties
13:27:17 <billroberts> ...it could work for specifying domains probably
13:27:55 <billroberts> ...But to have a good RDF representation of CoverageJSON, you would need a more complex pre-processor.  JSON-LD itself is not a good enough match
13:28:12 <billroberts> ...so CRS, time parameters, measures and units are a good case for RDF
13:29:00 <billroberts> ...and how to deal with ranges?  Duo's approach is also not doing pure RDF data cube, as the values are not simple numbers.
13:29:30 <billroberts> ,,, either a JSON array literal or a base64 encoded image are kind of equivalent - both need extra processing
13:30:15 <Maik> billroberts: good case for highlevel metadata like in dcat etc., but not range in RDF, but where exactly do you draw the line
13:31:05 <billroberts> maik: a timeseries at a single point could easily be pure rdf data cube
13:31:50 <billroberts> ...and there could be multiple representations of a single coverage
13:32:00 <billroberts> ...how coudl they be linked together
13:33:22 <Maik> Duo: we do timeseries entirely in RDF, each point own observation, independent
13:36:03 <Maik> http://the-iea.github.io/ecem/
13:36:13 <Maik> http://the-iea.github.io/ecem/app/data/ERA_Tmean_countries_sample.covjson
13:36:19 <billroberts> maik: has been developing something on another project, not MELODIES, where we have been using CoverageJSON for timeseries
13:36:50 <billroberts> https://json-stat.org/format/
13:37:44 <billroberts> some similarities between JSON-stat and CoverageJSON
13:38:13 <billroberts> maik: aware of it, also differences.  JSON-stat is always a single file, can't link to external resources for definitions etc
13:38:30 <billroberts> ...it uses arrays for many things, so not suitable for including any JSON-LD
13:39:06 <billroberts> ...it misses a proper object structure or extensibility
13:40:21 <Maik> billroberts: progress... I'll make contents list for what spec should contain
13:40:30 <Maik> ... take examples from other specs
13:40:46 <Maik> ... catch up with latest covjson stuff (tiling..)
13:41:12 <Maik> ... struggle how to turn discussions into actual agreements, things to decide, ...
13:42:51 <billroberts> maik: areas that are still open in Covjson - temporal reference systems (waiting for the Time subgroup to recommend something!); how to define different zoom levels on grids; how to link to different variants of a coverage in different CRS.  Should that go into the main core format, or handle it by extensions to it.
13:43:32 <billroberts> ...already have a simple format for a collection of coverages.  All coverages in it must have the same domain type
13:44:27 <billroberts> ...some formats have paging built into them.  Covjson doesn't.
13:44:39 <billroberts> ...so a few things still to do but mostly details. Generally it works well
13:45:07 <Duo> +q
13:45:14 <billroberts> ...how do  you decide complex parameters, for example 'air temperature at 2 metres height'
13:45:20 <billroberts> ack d
13:46:27 <Maik> Duo: dggs defines zoom levels, up to single point value
13:46:52 <Maik> ... unifies coordinate systems
13:48:06 <Maik> Maik: how does dggs solve plate movement problems (like lat/lon)
13:48:28 <Maik> Duo: split up into polygons, then squares
13:50:16 <Maik> Maik: are there clients that can handle it already?
13:50:33 <Maik> Duo: yes, there's one called... [...]
13:50:36 <Duo> http://rhealpix.r-forge.r-project.org/
13:51:47 <Duo> paper on dggs: http://raichev.net/files/rhealpix_dggs_preprint.pdf
13:52:19 <Maik> billroberts: come up with contents list until end of week
13:53:32 <billroberts> maik: concentrate on domain, range, parameters - don't get too involved in high level metadata
13:55:55 <billroberts> Yes, we can just refer to best practices from SDW or from DWBP for many of the high level things
14:00:18 <billroberts> maik: would prefer to use Github to author the spec document - better notifications etc
14:01:30 <Maik> also for issue tracking etc
14:01:34 <billroberts> RRSAgent, make logs public
14:01:38 <billroberts> RRSAgent, draft minutes
14:01:38 <RRSAgent> I have made the request to generate http://www.w3.org/2016/06/15-sdwcov-minutes.html billroberts
14:01:44 <billroberts> end of meeting
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