<div dir="ltr"><div><br>TL;DR - CADC implemented a prototype SODA services and use DataLink service descriptors to convey data-specific metadata and parameter info. The implementation demonstrates that with POS you cannot convey metadata so we introduced new positional cutout paramseters (CIRC and POLY) that conform to WD-DALI-1.1 xtypes (circle and polygon) and allow us to convey useful parameter metadata as a result.<br><br>Before anyone panics: we also show that POS, CIRC, and POLY can co-exist :-)<br><br>image dataset: ID=caom:IRIS/f212h000/IRAS-25um<br><br>* ObsCore-1.1 metadata *<br><br><a href="http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/sia/v2query?ID=caom:IRIS/f212h000/IRAS-25um">http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/sia/v2query?ID=caom:IRIS/f212h000/IRAS-25um</a><br><br>So, this is a dataproduct_type=image, calib_level=2, s_xel1 & s_xel2 say it is 500x500 (pixels)<br><br>* image links *<br><br><a href="http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/caom2ops/datalink?ID=caom:IRIS/f212h000/IRAS-25um">http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/caom2ops/datalink?ID=caom:IRIS/f212h000/IRAS-25um</a><br><br>Note the generic SODA service descriptors (not linked!):<br><br><RESOURCE type="meta" ID="soda-sync" utype="adhoc:service"><br> <PARAM name="resourceIdentifier" datatype="char" arraysize="27" <br> value="ivo://<a href="http://cadc.nrc.ca/soda#sync">cadc.nrc.ca/soda#sync</a>" /><br> <PARAM name="standardID" datatype="char" arraysize="*" <br> value="ivo://<a href="http://ivoa.net/std/SODA#sync-1.0">ivoa.net/std/SODA#sync-1.0</a>" /><br> <PARAM name="accessURL" datatype="char" arraysize="*" <br> value="<a href="http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/caom2ops/sync">http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/caom2ops/sync</a>" /><br> <GROUP name="inputParams"><br> <PARAM name="ID" datatype="char" ref="fileURIRef" arraysize="*" value="" /><br> <PARAM name="POS" datatype="char" ucd="obs.field" arraysize="*" value="" /><br> <PARAM name="CIRC" datatype="double" ucd="obs.field" unit="deg" xtype="circle" arraysize="3" <br> value="" /><br> <PARAM name="POLY" datatype="double" ucd="obs.field" unit="deg" xtype="polygon" arraysize="*" <br> value="" /><br> <PARAM name="BAND" datatype="double" ucd="em.wl;stat.interval" unit="m" xtype="interval" arraysize="2"<br> value="" /><br> <PARAM name="TIME" datatype="double" ucd="time;stat.interval" unit="d" xtype="interval" arraysize="2"<br> value="" /><br> <PARAM name="POL" datatype="char" ucd="phys.polarization.stokes" arraysize="2*" value="" /><br> </GROUP><br><br></RESOURCE><br><RESOURCE type="meta" ID="soda-async" utype="adhoc:service"><br> <PARAM name="standardID" datatype="char" arraysize="*" <br> value="ivo://<a href="http://ivoa.net/std/SODA#async-1.0">ivoa.net/std/SODA#async-1.0</a>" /><br> ... same params as above<br></RESOURCE><br> <br>params: ID, POS, CIRC, POLY, BAND, TIME, POL<br><br>Above and below you will see a resourceIdentifier param; this is there to support the use of a runtime registry lookup to generate the accessURL. Doing it this way allows us to generate URLs to development, test, or production servers depending on the work environment... our DataLink and SODA services are not actually registered but my intent is to make these resolvable by registering the services in the near future.<br><br>Likewise, the standardID values for SODA are not (yet) resolvable but they will be...<br><br>The link-specific SODA descriptors (the ID attributes have UUIDs in them) e.g.:<br><br><RESOURCE type="meta" ID="soda-cbb62ed5-c2c9-4dd9-aed6-46d7d5173dca" utype="adhoc:service"><br> <PARAM name="resourceIdentifier" datatype="char" arraysize="27"<br> value="ivo://<a href="http://cadc.nrc.ca/soda#sync">cadc.nrc.ca/soda#sync</a>" /><br> <PARAM name="standardID" datatype="char" arraysize="32" <br> value="ivo://<a href="http://ivoa.net/std/SODA#sync-1.0">ivoa.net/std/SODA#sync-1.0</a>" /><br> <PARAM name="accessURL" datatype="char" arraysize="*" <br> value="<a href="http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/caom2ops/sync">http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/caom2ops/sync</a>" /><br> <GROUP name="inputParams"><br> <PARAM name="ID" datatype="char" ucd="" arraysize="*" value="ad:IRIS/I212B2H0" /><br> <PARAM name="POS" datatype="char" ucd="obs.field" arraysize="*" value="" /><br> <PARAM name="CIRC" datatype="double" ucd="obs.field" unit="deg" xtype="circle" arraysize="3"<br> value=""><br> <VALUES><br> <MAX value="140.63049941314583 0.2007826788236291 8.778341996040131" /><br> </VALUES><br> </PARAM><br> <PARAM name="POLY" datatype="double" ucd="obs.field" unit="deg" xtype="polygon" arraysize="*"<br> value=""><br> <VALUES><br> <MAX value="146.83673628162285 -6.408995958971017 134.3808989000012 -6.370135804011464 134.4242625446688 6.007430601323759 146.8700273500712 5.96918267453771" /><br> </VALUES><br> </PARAM><br> </GROUP><br></RESOURCE><br><br>The value for the ID parameter is specified in the value attribute because this is a file-specific (at CADC) service descriptor and it needs this file. This *is not* the same kind of ID that one uses to call the DataLink service (that is a publisher_did which we will be changing into a resolvable ivo-id once I'm happy with the registration of our collections; this is a file identifier from our storage system). I could have used a ref attribute to the links table (since the file URI is there for our other services and for the generic soda service descriptors) but once you have link-specific descriptiorsd anyway this seems tidier (e.g. I'll eventually be able to remove the custom fileURIref column from our links table).<br><br>BAND, TIME, and POL are missing because this is a 2D image so cutouts on those axes are not possible.<br><br>POS is listed there because positional cutout is possible, but I don't see a sane way to convey sensible values to help someone use POS; the client has to know the extent (from data discovery) or get it in some other way (metadata capability).<br><br>For CIRC and POLY the service includes a "maximum sensible extent" with which to perform cutouts. The value attribute of the MAX element is a string and my interpretation of the intent is that the client should interpret it as the same "type" of thing as the PARAM in which it is found. It feels like the MAX extent conveys useful and sensible information, but I didn't see anything useful to put in MIN. Is this an abuse of MAX? Maybe (in the sense that MAX usually implies that there is an ordering) but given the implied type consistency that is already there people are interpreting this now and when I showed this to a few techy astronomers that understand VOTable they interrpetted this as I meant it. (The CIRC MAX is the minimum spanning circle; the POLY MAX is the polygon boundary -- so using those values would get all the pixels.)<br><br>Right now, CIRC and POLY are my own custom parameters and they should not bother a strict client that used this descriptor because of the standardID. I chose different parameter names so i could be more explicit about the value metadata (datatype, arraysize, xtype, units, ucd -- WD-DALI-1.1) *and* so I could provide the "maximum value" of the exact same type. In the SODA service this is very straightforward to implement (I use the same Format classes for reading and writing VOTables and for parsing and validating SODA params).<br><br></div><div>For these URLs, I recommend just "curl -v" so you can see the HTTP headers, but you can download the data if you want to :-)<br><br>* image cutout: POS *<br><a href="http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/caom2ops/sync?ID=ad:IRIS/I212B2H0\&POS=circle%20140.5%200.0%200.5">http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/caom2ops/sync?ID=ad:IRIS/I212B2H0\&POS=circle%20140.5%200.0%200.5</a><br><br>decoding the redirect url: cutout=[0][235:275,238:278,*]<br><br>* image cutout: CIRC *<br><a href="http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/caom2ops/sync?ID=ad:IRIS/I212B2H0\&CIRC=140.5%200.0%200.5">http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/caom2ops/sync?ID=ad:IRIS/I212B2H0\&CIRC=140.5%200.0%200.5</a><br><br>decoding the redirect url: cutout=[0][235:275,238:278,*]<br><br>* image cutout: POLY *<br><a href="http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/caom2ops/sync?ID=ad:IRIS/I212B2H0\&POLY=140%200.0%20140.5%200.0%20140.5%200.5%20140.0%200.0">http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/caom2ops/sync?ID=ad:IRIS/I212B2H0\&POLY=140%200.0%20140.5%200.0%20140.5%200.5%20140.0%200.0</a><br><br>decoding the redirect url: cutout=[0][255:275,258:278,*]<br><br>If successful, these SODA requests to /caom2ops/sync respond with an error message or a redirect to a URL with a pixel cutout using cfitsio syntax. That is completely an implementation detail of our archive infrastructure and not part of the prototype per se.<br><br>If they fail (easy to do, just mess with the params) the response (after redirect) is text/plain with a suitable HTTP status code.<br><br><br><br><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On 29 February 2016 at 16:03, Patrick Dowler <span dir="ltr"><<a href="mailto:pdowler.cadc@gmail.com" target="_blank">pdowler.cadc@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div><div><div><div><div><div><br></div>I have finally finished and deployed our latest prototype SODA services and augmented our DataLink service to provide service descriptors to enable use of SODA. This works spans several services so, following Markus' "gripes" appoach I will try to separate things into separate messages, but I'll just make the messages replies to this one so they will be a single thread and I promise to put the TL;DR at the top of each :-)<br><br></div>So, coming up:<br><br></div>1. description of datalink service descriptor output and soda sync cutout of a 2D image<br><br>2. less wordy description of datalink service descriptor output and soda sync cutout of a 3D cube<br></div><br>3. description of datalink service descriptor output and soda async cutout(s) of a 2D image<br><br></div>It is quite a lot to look at, but I would like to point out here that implementing the whole end-to-end usage forced me to reconsider some earlier decisions and refine things to make them more clear and more useful. Although DataLink and SODA are loosely coupled in a technical sense, they do need to get along and work together and each has some effect or influence on decisions one takes while implementing the other.<br><br></div>more to follow...<br><div><div><div><div><br>--<br> <div><div><div><div><div><div dir="ltr"><div><div>Patrick Dowler<br></div>Canadian Astronomy Data Centre<br></div>Victoria, BC, Canada<br></div></div>
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</blockquote></div><br><br clear="all"><br>-- <br><div class="gmail_signature"><div dir="ltr"><div><div>Patrick Dowler<br></div>Canadian Astronomy Data Centre<br></div>Victoria, BC, Canada<br></div></div>
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