Re: BP document FROZEN - vote next Monday [SEC=UNCLASSIFIED]

Hi Bruce -

I've updated the BP doc to incorporate some of your comments. See PR #796
[1]

Before I go into details, let me say:
1/ I have an outstanding action to update section 11 - your commentary is
useful and I will try to incorporate that
2/ you ask what's driving the deadline? the SDW WG Charter expires at the
end of June, and when you factor a 45-day vote in for OGC, we're already a
little over. We plan to freeze the document on Monday 8-May, with a WG vote
to release on Wednesday 10-May, then there will be a OGC TC presentation
(via webinar) on Friday 12-May. Then begins the 45-day vote which will be
running while the St. Johns TC happens.

So - looking back at the feedback you gave (on 13 Apr)

A/ Section 5 Spatial Things: I have added The Sahara as an example of a
spatial thing with fuzzy boundaries
B/ Section 6 Coverages: You're right that conceptually, a coverage has
extent. While some may see it just as a data structure, I think it is more
convenient to think of a coverage as a type of spatial thing with some
particular characteristics. I've updated the text to reflect this more
flexible approach
C/ You suggest that "a discussion on how ‘spatial things’ are
conceptualised as ‘objects’/features/coverages etc could be useful" - but
this is potentially a huge & complex topic in and of itself. We have
attempted to give a light touch to 'conceptualising' spatial things in
Section 5; and Section 6 describes how spatial things (features) and
coverages may be related. Early on, the WG agreed that we would not try to
provide advice on [semantic] data modelling. DWBP [2] (which we refer to)
talks about data modelling (or at least picking the right vocabulary) to
some degree I think. Without adding a whole new section, I'm struggling to
see what changes I might make to the SDW BP doc.
D/ Section 7 Spatial Relations: I think that the current text is correct
here - certainly, it is drawn from trustworthy sources. You also suggest
adding a discussion about spatial joins. Again, I smell trouble here. If B
is within A, then figuring out which properties from A also apply to B is a
complex problem for which you need to have a good understanding of the
semantics; it's similar to determining is to resources are actually the
same (correlation etc.) - "Here be dragons" we said. I said earlier that
the WG has shied away from semantics, because our focus is on the spatial
aspects. And yes, you could argue the a spatial join is a spatial aspect,
but it does rely on the understanding of the semantic model which is domain
dependent. Finally, I'll add that we have unashamedly focused on _data
publication_; spatial joins are a usage concern. Given the limited
resources we have available in the group, we sadly can't cover all the
problems.
E/ Section 8 CRS: I covered this in a separate email and PR
F/ Section 10 SDI: Apologies if it reads that we have an overly pessimistic
view of SDIs. I tried to assert that SDIs are a necessary part of managing
spatial information. The challenge is that they are not easy to use by
non-experts. I totally agree that SDIs are more than the discovery
catalogue! On the subject of discovery metadata, we have a whole best
practice (BP13 [3] - sorry, we changed the numbers) devoted to dataset
metadata; and BP2 [4] talks about the role that that dataset metadata has
in making the spatial data discoverable by getting stuff indexed by search
engines. So I think that we're really not throwing out babies and bath
water together :-)

That's all for now.

If you're content with these changes, that's good. If there's still stuff
you're struggling with, then you have two options:
1/ provide some text for us to incorporate ... remember we want to freeze
the document by Monday 8-May
2/ wait for the OGC vote (starting 12-May) and provide feedback about your
concerns there ... the earlier the better, then we stand a better chance of
being able to respond.

Oh- one more thing. The SDW Best Practice doc is a W3C Note, which means it
can be updated. There is a plan to create a Spatial Data on the Web
'community group' that will carry the work on.

Best Regards, Jeremy

[1]: https://github.com/w3c/sdw/pull/796
[2]: https://www.w3.org/TR/dwbp/
[3]: http://w3c.github.io/sdw/bp/#spatial-info-dataset-metadata
[4]: http://w3c.github.io/sdw/bp/#indexable-by-search-engines

On Wed, 19 Apr 2017 at 08:22 Bruce Bannerman <bruce.bannerman@bom.gov.au>
wrote:

> Hi Jeremy,
>
>
> I've just had a quick scan through the rest of the best practice.
>
>
> This document needs time for a decent sanity check.
>
>
> It is quite technical and assumes quite a bit of prior knowledge.
>
>
> I suspect that we may be missing the needs of the targeted audience (that
> I'm assuming to be a Web Developer).
>
>
>
>
> As an example under 11.4 Parse that, there is the text:
>
>
> "Imagery formats JPEG [JPEG2000
> <http://w3c.github.io/sdw/bp/#bib-JPEG2000>] and PNG [PNG
> <http://w3c.github.io/sdw/bp/#bib-PNG>] can also be coerced to carry
> data; providing 3 or 4 channels of 8-bit data values."
>
>
> An end user would need to understand that imagery is typical presented as
> a set of bands of data, where each band is a segment of the Electromagnetic
> Spectrum.
>
>
> Using the example of a set a 7 bands within a Landsat 7 scene, only three
> bands are typically presented in a JPEG/PNG file as RGB values. These
> RGB values in the file may actually depict a different band combination
> from the image, e.g. data from Blue, NIR and MIR bands.
>
>
> The paragraph goes on to discuss the need to avoid compressed data, but
> does not discuss lossy and non-lossy compression algorithms.
>
>
> Lossy compression should be avoided (as stated), but lossless may well be
> OK.
>
>
> Though this will also depend on intended use. If the data is just to be
> used as a 'pretty picture' background then the lossy format is probably OK.
>
>
> The JPEG2000 image format that is used as an example is typically
> compressed with a wavelet compression. This is usually a lossy compression,
> unless the data creator has explicitly created a lossless image.
>
>
>
> This is only one example that I was able to quickly find for this email.
>
>
> =====
>
> What is driving the current rush to finish this work? Is the deadline just
> arbitrary that someone has pulled out the air?
>
> =====
>
>
> There is a lot of good work in this document. I'd like too see it undergo
> a rigorous edit and sanity check.
>
>
>
> I will have to leave this version of the document now, as I really do have
> other priorities that I need to concentrate on.
>
>
>
> Kind regards,
>
>
> Bruce
>
>
>
> ​
> ------------------------------
> *From:* Jeremy Tandy <jeremy.tandy@gmail.com>
> *Sent:* Thursday, 13 April 2017 3:54 PM
> *To:* Bruce Bannerman; Tandy, Jeremy
> *Cc:* public-sdw-wg@w3.org
> *Subject:* Re: BP document FROZEN - vote next Monday [SEC=UNCLASSIFIED]
>
> Hi Bruce. This is all good input which I will weave into the draft ...
> many thanks for your efforts!
>
> Our dates seem to have got crossed though :-)
>
> The "Monday" in the email title was back in March ahead of the TC meeting
> in Delft! We voted to release that draft anyway.
>
> Currently, we expect to have a _FINAL_ draft (pending editorial fixes etc)
> ready for vote on 26 April ... however I've just picked up an extra week of
> week that was unexpected so we may slide that a little.
>
> So-
> 1/ thank you
> 2/ there's still time for more :-)
> 3/ incorporating the outcomes from the CRS thread is on my to-do list
>
> Happy Easter!
>
> Jeremy
> On Thu, 13 Apr 2017 at 06:24, Bruce Bannerman <bruce.bannerman@bom.gov.au>
> wrote:
>
>> Hi Jeremy,
>>
>> I’m not going to get the time to review this BP within the timeframe
>> required by SDWWG.
>>
>> I’ll send you what I have to date. You may be able to do something with
>> it.
>>
>>
>>
>> 5. Spatial Things
>>
>>    - I recall that there was some discussion on imprecisely defined
>>    locations. Where did we get to with this.   Some examples:
>>
>>
>>    - The Mara-Serengeti ecosystem
>>       - The Great Barrier Reef
>>       - Dogger Bank
>>       - West of the Black Stump
>>       - The Sahara
>>       - the coastline
>>       - The Western Australian Greenstone belt
>>       - The Mary River floodplain
>>
>>
>>    - These could also be considered 'Spatial Things’, we just can’t
>>    reliably define their locations with crisp vector boundaries.
>>
>>
>> 6. Coverages
>>
>>    - I note the statement about coverages not being a 'spatial thing’.
>>
>>
>>    - This is quite constraining and implies that only vector data can be
>>       a 'spatial thing’.
>>
>>
>>    - Following on from my comments in response to 2 above, many of these
>>       features are best represented with imprecise ‘fuzzy’ boundaries. A coverage
>>       is a good way of handling this.
>>
>>
>>
>> On  5. Spatial Things  and  6. Coverages
>>
>>    - I don’t like the artificial delineation between ‘spatial things’
>>    and Coverages.
>>
>>
>>    - Both are conceptually ‘Spatial Things’
>>
>>
>>    - We are just talking about vector and raster data in different terms.
>>
>>
>>    - A ‘Spatial Thing’ could be represented using both raster and vector
>>       representations, depending on the context of what the representation is to
>>       be used for.
>>
>>
>>    - This is probably where a discussion on how ‘spatial things’ are
>>       conceptualised as ‘objects’/features/coverages etc could be useful. It
>>       could bring in discussions on scale, precision, accuracy, intended use etc.
>>
>>
>>    - I do like the the linkage between a real world concept and multiple
>>    representations of that concept. It will allow us to overcome a long term
>>    issue inherent in spatial data modelling.
>>
>>
>>
>> 7.  Spatial Relations
>>
>>    - Topological Relations
>>
>>
>>    - Topology is more about the connectedness of features e.g.:
>>
>>
>>    - Network trace, upstream, downstream
>>          - Left of, right of
>>          - Etc
>>
>>
>>    - The examples given are conflating topology with spatial overlay
>>       functions, e.g.
>>
>>
>>    - Intersects, Overpaps, Point in poly, Buffer, etc
>>
>>
>>    - Perhaps a brief discussion on 'spatial joins’ may be also
>>    appropriate here, where the attributes of one feature can potentially be
>>    assumed by another feature due to their spatial co-location, e.g.:
>>
>>
>>    - 'this building’ is located in 'this census district', therefore I
>>       infer that the census attributes for 'this census district’ apply to the
>>       residents of ’this building'
>>
>>
>> 8. CRS
>>
>>    -
>>
>>    See my comments in the related email. They are still relevant as
>>    noted by Byron in his email of 4 April.
>>
>>
>>
>> 10. SDI
>>
>>    - This document takes an overly pessimistic and narrow view of SDIs.
>>
>>
>>    - SDIs are more than just a Discovery Metadata catalogue.
>>
>>
>>    - They are defined as "the base collection of technologies, policies
>>    and institutional arrangements that facilitate the availability of and
>>    access to spatial data”. See the SDI Cookbook [1], Chapter 1, SDI.
>>
>>
>>    - Discovery metadata records *can* be very useful for determining the content
>>    of a given spatial dataset and its intended use. They are very useful to
>>    use to determine if it is appropriate to use the data set for a purpose
>>    other than that for which it was created.
>>
>>
>>    - What would be useful is if a way could be found to make these
>>    metadata records within the catalogues indexable, together with a way of
>>    linking the Discovery Metadata record to the Spatial Data Service(s) that
>>    provide access to this data. This is where there is considerable potential
>>    for linked data. And yes these services could be configured to provide
>>    GUID’s for spatial things, just don’t throw the baby out with the bathwater.
>>
>>
>> Sorry, that is all that I’ve been able to get to.
>>
>> Kind regards,
>>
>> Bruce
>>
>> [1]
>> http://gsdiassociation.org/images/publications/cookbooks/SDI_Cookbook_from_Wiki_2012_update.pdf
>>
>>
>>
>> From: Linda van den Brink <l.vandenbrink@geonovum.nl>
>> Date: Thursday, 16 March 2017 at 20:04
>> To: "SDW WG (public-sdw-wg@w3.org)" <public-sdw-wg@w3.org>
>> Subject: BP document FROZEN - vote next Monday
>> Resent-From: <public-sdw-wg@w3.org>
>> Resent-Date: Thursday, 16 March 2017 at 20:04
>>
>> Hi all,
>>
>>
>>
>> The BP document is FROZEN and ready for people to read/review at
>> http://w3c.github.io/sdw/bp/.
>>
>>
>>
>> A massive amount of work has been done during this sprint. To summarize:
>>
>> - Section 8 CRS, BP1, BP3, BP6, BP8, BP9, BP10, BP11, BP14, BP17 updated
>>
>> - BP2, BP12, BP13, BP15, BP16, Section 12.8 (Dealing with large
>> datasets), Section 14 Narrative removed
>>
>>
>>
>> A full account of the changes is in the sprint plan[1].
>>
>>
>>
>> VOTE is scheduled for MONDAY 20-3-2017 during the face to face meeting in
>> Delft.
>>
>>
>>
>> Special thanks to Andrea, Josh, Clemens, Bill, Ed, and Byron for putting
>> in the hours this sprint!
>>
>>
>>
>> Linda & Jeremy
>>
>>
>>
>> [1]:
>> https://www.w3.org/2015/spatial/wiki/Detailed_planning_BP_document#February_-_mid_March_2017
>> :
>>
>>