Articles from Meetings

• We are at the AG-Tagung in Bremen

  2022-09-13 Markus Demleitner

  

  Our puzzler prize for this year (well, its lower part): The Hertzsprung-Russell diagram according to Gaia on a wonderfully soft towel.

  After two years of “virtual” meetings, this year the venerable “Herbsttagung der Astronomischen Gesellschaft”, the meeting of Germany's Astronomical Society, is back. Almost as before Corona, it is bringing astronomers together, this year in Bremen (previously on this blog: 2018 in Stuttgart).

  Bowing to the “German“ in GAVO, this is an opportunity for us to connect to the (or, rather, our) community, both with a splinter meeting and with our traditional booth, at which you can pick up various edifying printed matter, a laminated ADQL reference card, and lots of VO wisdom (i.e., chat with our friendly booth staff).

  And you can solve our puzzler, a little problem that has an elegant VO-based solution (previous puzzlers). As is tradition, solving the puzzler will not only give you intellectual satisfaction and perhaps even insights into the VO, it will also give you a chance to win an item that is heavenly fluffy. The article photo shows this year's puzzler prize, and if this piques your desire, absolutely feel free to hand in solutions even if you are not in Bremen[1].

  Update 2022-09-15: This year's prize went to Bonn. So, there's no point to hand in solutions any more – rather, have a look at how we thought the problem should be approached.

  [1]	We've had an actual award (the AG-RAS Carolin Herschel medal) being handed out virtually yesterday, so in case we really draw a remote entry, I am very confident that we can work something out for handing over the prize.

• It's Interop Time Again

  2022-04-26 Markus Demleitner

  

  A little ego booster in DAL I: Baptiste and Chloe discuss a feature for incremental harvesting of remote databases using odbcGrammar that I have implanted into DaCHS late last year.

  This morning at seven CEST the first Interop of this year started: It's time again for everyone involved in the VO to come together, tell each other what happened since the last Interop and plan for the next steps. The meeting is purely digital again, and again the schedule is a bit crazy in order to evenly spread time painsj across the globe: there are sessions in the relatively early morning CET, in the late afternoon, and fairly late at night.

  Fairly late at night (by my standards) is now, when I'm listening to the talks in a session of the Data Access Layer working group trying to work out how to do multiple cutouts in one request using SODA, something I've been rather skeptical about while we were coming up with the spec in the mid-2010s: Going from “single value“ to “sequence“ generally complicates matters by something like an order of magnitudes, and with HTTP 1.1 – which lets you run multiple requests in a single connection – doing multiple requests is cheap.

  In contrast, SODA doesn't really say what a service should do if, say, there are multiple positions in a cutout request: should the regions be merged (that's what DaCHS does)? Should multiple images come back? If so, how: in a tar, in a multi-extension FITS, in some other way? What happens if you give both multiple positional and spectral ranges: should there be one result per element of the cartesian product? And if it works that way: should clients have a chance to figure out what combination of parameters produced which result dataset?

  In all that mess, it's gratifying to see that my compromise proposal from way back when – if we do multi-cutout, let's do it by uploading a table specifying one cutout, including a label, per row – to be floated again. But very frankly: My vote would still be to deprecate repeated POS, CIRCLE, BAND, and friends in SODA: requests are cheap these days.

  Oh, and while I'm confessing emotions of perhaps not entirely unselfish gratification: I still rejoice when I see DaCHS applications discussed in public, as Chloé and Baptiste did in their talk.

  Update at 2022-04-27, Morning

  The “virtual” Interop may not be quite as exciting as the real thing, but at least the jetlag is back.

  Yesterday at midnight I gave a talk on requirements and validators, which really was an elaboration of some of the ideas I developed on this blog a month ago. If I may say so myself, I've grown fond of the classification of MUST-s into, in the end, items the machines need, items the users need, admonishments for implementors, and items that we believe the future may need. I'm sure there are more, but even for these I found it remarkable that the less will immediately break if someone violates a piece of a spec, the more important validation becomes. This again is one of these thoughts that feel as if someone probably has pondered them a lot more deeply before…

  I also was really happy about Mark's pitch for validating specifications themselves that kept me awake until one a.m. CEST. In my authoring system ivoatex, I've introduced a hook to allow for a test target, and Mark kindly supported that effort by adding an xsdvalidate subcommand to the excellent stilts. The ivoatex documentation then grew some advice on what and how to test; in case you're writing or maintaining IVOA specs: do have a look. Mark's talk has a few great examples where spec-time validation would have saved a lot of effort and embarrassment.

  Only six hours later, I was back in <expletive deleted> zoom to listen to the Grid session, which again featured Mark, apparently unfazed by the lack of sleep, talking about (potentially) federated authentication outside of the browser (which is something I really want for persistent TAP uploads).

  And then there was the joint time domain/radio session. The slides are not yet there, but once they are, do yourself a favour and at least look at the beautiful images Dougal showed – Radio by now can make about as pretty pictures as Optical – and Alan's talk with the hypnotic sensitivity maps that again showed that low-frequency radio astronomy, seen from outside, is even more of an arcane art than is its high-frequency sibling.

  Update at 2022-04-27, late evening

  For me, this Interop has a strong proper motion slant. In this afternoon's Apps session, I tried to sell an extension to COOSYS I've wanted for a long time, just enough to do epoch propagation.

  You see, ever since my first serious contribution to the VO standards universe, the proposal on doing STC annotation in VOTable in 2010, failed miserably because almost nobody took it up, I have struggled to still somehow get enough annotation added to VOTables to let clients apply proper motions automatically.

  Given there are now data models for Coordinates and what we call Measurements (which roughly is errors and, well, a bit of physics) on the way, I figured this might be a good time to finally fix the COOSYS VOTable element. For one, data centers will revisit the STC annotation anyway if the models and the VOTable data model annotation will pass the reviews, and producing an improved COOSYS would then almost come for free.

  But I can't lie: after the experiences of the past I'd also love to have a fallback position in case we spend another ten years on data models and annotations without getting anywhere. 25 years after the VO's birth epoch (if you will) of J2000.0, many stars have already moved of order of an arcsecond from where our first big catalogues saw them, and so we can ill afford to wait these extra ten years.

  Not surprisingly, the proposal resulted in quite a bit of pushback, perhaps even a bit more than I had expected. Well: I should have given this talk years ago.

  The proper motion topic will come back tomorrow in the second DAL session, when I will talk about ADQL user defined functions to do epoch propagation. This talk will feature one of the prettier plots I've produced in the last few months:

  

  What happens if you propagate positions when all you have are proper motions (i.e., no parallaxes and no distances) and you do that naively (blue), in the tangential plane (red), and under the assumption of a purely tangential motion. The lecture notes tell you how to come up with the data plotted here.

  I think I can safely predict you will read more about some of these UDFs on this very blog later this year.

  Update 2022-04-28, late evening

  Today felt the most conferency so far for this Interop, and perhaps for any “virtual conference“ I've attended. I believe there's a technical reason for that. After the second proper motion-flavoured talk I've just mentioned – that was still using, sigh, zoom –, things mostly happened in gathertown, a platform you can actually walk around in, stand together and don't always talk on stage as in zoom. Fervently believing in the mantra of “protocols, not platforms” (of course: this is the VO), I shouldn't be saying this, but: I actually like gathertown.

  And so I guess we made quite a bit of progress in little side meetings and a hackathon on things like LineTAP (which, I hope, will bring all the rich data on spectral lines from VAMDC to the VO); how to let people have continuous integration checks against their Jupyter notebooks to notice in time when we're breaking something (my recent brown-bag pyvo bug that has somwhat started this was actually mentioned as a positive example in a talk (slide 19); and: it turned out I'm not the only notebook skeptic on this planet!); how we ought to define “facility” and “instrument“ in Obscore and the Registry (and, probably particularly insiduously, in SSAP, where what's called “facility“ there should probably be what's called “instrument“ elsewhere – sigh), a topic we already had touched yesterday, which in turn has resulted in Tamara's mail; an interesting service DaCHS operators want to run that would return PDF files as what DaCHS calls a “product” (which would normally be a thing like a FITS file); and then some more, including, of course, idle chatting.

  That was almost as good as an actual meeting.

  Update 2022-04-29, afternoon

  This morning, I chaired a nice and lively Semantics session, where I talked about the move of our Vocabulary maintenance to github. That particular thing did not elicit a lot of comments, not even when I extended an invitation to perhaps amend Vocabularies in the VO 2 in other weys. I'll take that as some sort of reassurance that I did a reasonably good job designing that thing, although I cannot entirely rule out that people just did not have enough time to find the warts.

  One thing I will call out at tonight's closing penary is Stéphane's talk on vocabularies in EPN-TAP. The way he was looking at the various word lists involved in that standard, looking at what “just works“, where the concepts are probably too special to worry about, and then the clumsy space in between – where there are or should be vocabularies that almost, but not quite fit – was exemplary. I'm looking forward to followups on the mailing lists, trying to work out where we can perhaps align different concept hierarchies so we spare implementors duplicate efforts. And figuring out where that's impossible, too expensive, or in other ways undesirable, and where the problems are. I suppose there's a lot to be learned from that.

  Another high point was the identification of Wikidata as a valuable resource for the never-ending story of creating identifiers for instruments and facilities in Baptiste's talk. There is some special gratification in making our activities matter beyond the VO, link our resources with the wider RDF world – and hack SPARQL.

  What's left for me is the Registry session, where I will briefly report, in particular, on my most recent effort of getting rid of my venerable GloTS service by adding a table of TAP-queriable tables to RegTAP. Let's see what people say – but in the end the challenge will be to convince the other operators of RegTAP services to take up the proposed changes. The central challenge there is that part of it is built on MOCs, and while the ESAC registry is built on Postgres that can already taught to deal with them, the one at MAST is based on SQLServer, which, I think, cannot yet. Let's see.

  Another thing I'm looking forward to is Hendrik's pitch for registring tutorials and similar educational material. I'd really like to see more stuff on VOTT, which is fed from such registrations.

  Update 2022-04-29, late evening

  Interops for me always have something of an ego trip when I see traces of my activities in other people's work. And I've just discovered such a trace in a place I had not expected it: Gilles' talk on extra metadata in service responses, where he showed metadata DaCHS returns with its TAP responses. This was in this morning's session of the Data Curation and Preservation interest group that, I have to admit, I skipped in favour of a proper breakfast without a screen in front of me.

  And he touched a topic that's dear to my heart, too. Really, I've been struggling to give applications enough metadata such that they can simply spit out a bunch of BibTeX for the sources used in a particular VO workflow for quite a while. In typcial DaCHS responses, you will find a bibcode and often a link to BibTeX (example), and at least the container element I got standardised in DALI 1.1. Let's see what else we can specify so that machines can reliably extract such information: Authors? Technical contact addresses? Date and time of production (could be very relevant for evolving data)? Full provenance? Well: If you've ever missed some piece of metadata, this would be a good time to bring it up.

  All that's left now is the reports of the Working Groups (which will be another midnight talk for me) and a bit of farewell ceremony. After that, I'll go to sleep, and so that's it for my Interop reporting.

• The 2021 Southern Spring Interop

  2021-11-05 Markus Demleitner

  

  A contribution for the ”things that didn't work out” (“Arbeiten, die zu keiner Lösung geführt haben”) section in our reports to BMBF: an attempt to systematise product types at the last Interop. I've made a new proposal at this Interop, and there is reason to hope it will fare better.

  Last night, the second IVOA Interop conference of 2021 came to an end; I'm calling it ”southern spring” because notionally, it happened in Cape Town, back to back with this year's ADASS. In reality, it was again an online event, and so, in keeping up with the tradition established in the pandemic times, the closing event was around midnight CET. I cannot say I will miss these late-night events, although I would not go as far as some people at the conference who quipped they'd prefer the airport security checks to having to sit through another zoom marathon.

  My contributions at this interop again had a clear focus on semantics, for instance with my public confession that my attempt to systematise “product types” at the last interop was entirely misguided; trying to force concepts like “time series”, “spectrum“ or “image” into a tree does not lead to anything that actually works for what this is intended to do, that is, helping people find the sort of data they are after for a particular purpose, or helping clients route data products to other clients better suited to process them. I will now try a restart using SKOS, a plan that was met with a lot more agreement than that previous attempt. Some entertainment at the side was provided by the realisation that a “time-image cube“ is normally called a movie. Next time I'll take in moving pictures, I'll find out what people say when I claim to investigate a time cube.

  Another talk that took up a topic from the last Interop's Semantics session was about making an IVOA vocabulary of object types based on the work done within the CDS over the last 40 year or so. This certainly is just the beginning of a longer effort, not the least because the current concepts severely fall short in the area of the solar system. But it's a start, and there's plenty of time to elaborate this before it will go through a review, presumably with the next version of Obscore.

  Also semantics-related, but over in the session of the Operations interest group, Mark Taylor reported on his activities to evaluate the standards adherence of semantics information in published tables. This activity is what had triggered me to make DaCHS validate UCDs assigned to columns in summer, something that I expect will result in quite few diagnostics when DaCHS operators upgrade to DaCHS 2.5 (expected for November). But that's fine: making it more likely that computers will actually recognise a, say, error in proper motion for what it is is undoubtedly a good thing. I'm therefore glad that there is almost a million “good” UCDs out there and a lot fewer somehow “bad”. I had expected much worse after my realisation that my own annotations left a lot to be desired in summer. By now, the only bad UCDs I'm still pushing out are the ones mandated by SSAP and SLAP. The contradictions between those standards and UCD are going to be addressed with Errata in the coming months.

  My talk in the third Apps session on Thursday afternoon still had some relationship with Semantics; it was a quick show and tell on the enhancements to WIRR I had reported on here in July, and it in particular showcased obtaining UCD constraints by full-text searching the rr.table_column table in my RegTAP service and the selection through UAT concepts. Satisfyingly in some way, it were these topics that people took up in the discussion after the talk. Less satisfyingly, people playing with the thing afterwards turned up something that has the alarming taste of a bug in the new MOC operations in pgsphere. Ouch.

  This segues into the realm of Registry, where there was no actual session but a rather well-attended side meeting in the gathertown instance we could take over from ADASS (that, incidentally, was substantially better attended than during the previous meetings). There, I mainly presented (and explained) my proposed changes to pyVO's registry interface currently living in a private branch in my fork on github. I will write a bit more on that around the time I will turn that into a PR.

  Another outcome of this was that there was some interest to turn the note on documents in the Registry – which is what feeds VOTT – into either an endorsed note or perhaps a Recommendation of the Registry WG.

  My fourth “proper” (in the rather twisted sense of: in a zoom session) talk was an attempt to finally do something about the problems pointed out in my caproles note lamenting that our current service registration patterns are fundamentally flawed. It proposed some ways to to get VOSI availability fixed, and the outcome was that we probably will drop what we currently require in that field, not the least because these requirements are cheerily ignored by 98% of the resources in the Registry.

  Those were again three fairly long days, usually starting with sessions around 7:00 CET and ending with sessions around midnight. Which is clearly not healthy. But on the other hand, it somehow does convey a physical sense of the global nature of the Virtual Observatory, on which people in many, many time zones work. And that, I have to say, still is something I do appreciate.

• GAVO at the Northern Spring Interop 2021

  2021-05-28 Markus Demleitner

  As usual in May, the people making the Virtual Observatory happen meet for their Interoperability Conference, better known as the Interop – where “meet” still has to be taken with a generous helping of salt (more on this near the end of this post). As has become customary on this blog, let me briefly discuss contributions with a significant involvement of GAVO.

  A major thing from my perspective actually happened in the run-up: The IVOA executive committee (“Exec“) approved Version 2.0 of Vocabularies in the VO, a standard saying how hierarchical word lists (“vocabularies“) can be managed, disseminated, and consumed within the VO. Developing the main ideas from sufficiently restricting RDF to coming up with desise (which makes complicated things possible with surprisingly little code), and trying things out on our growing number of vocabularies took up quite a bit of my standards time in the last 20 months or so – and I'm fairly happy with the outcome, which I celebrated with a brief talk on programming with IVOA semantics during Wednesday morning's semantics session.

  In that session I gave a second, more discussion-oriented, talk, probing how to formalise data product types – which is surprisingly involved, even with the relatively straightforward use case “figure out a programme to handle the data“: What's a spectrum? Well, something that maps a spectral coordinate to... hm. Is it still a spectrum if there's multiple sorts values (perhaps flux, magnitude, and polarisation)? If we allow, in effect, tuples, why not whole images, which would make spectral cubes spectra – but of course few client programmes that deal with spectra do anything useful with cubes, so clearly such a definition would kill our use case. And what about slit spectra, mapping a spatial coordinat to spectra?

  All this of course is reminiscent of the classical problems of semantics: An elephant is a big animal with a trunk. But when an elephant loses its trunk in an accident: does it stop being an elephant? So, much of the art here is finding the sweet spot of usability between strict and formal semantics (that will never fit the real world) and just tossing around loosely defined strings (that will simply not be machine-readable). After the session, I came up with the 2021-05-26 draft of product-type. If you read this a few years down the road, it might be interesting to compare with what product-type is today. I'm curious myself.

  Later on Wednesday CET, I did a shameless plug for my Datalink-transforming XSLT (apologies for a github link, but I'm fishing for PRs here; if you use DaCHS, you'll get the updated stuff with version 2.4, due soon). The core of this dates back to the dawn of datalink, but with a new graphical cutout code and in particular vocabulary-based tree-ification of the result rows, I figured it's time to remind the operators of datalink services it's still out there for them to take up. Perhaps more than from the slides, you can see what I am after here by just trying the Datalink examples I've collected for this talk and comparing document source, the appearance without Javascript (pure XSLT) and the appearance with Javascript (I'm a bit ashamed I'm relying so heavily on it, but much of this really can only be done client-side).

  Quite a bit after midnight my time (still Thursday UTC), Mark Taylor talked about Software Identification, something I've been working on with him recently. It's is one of the things that is short and trivial but that, when unregulated, just doesn't work; in this case it's servers and clients saying what they are when they speak HTTP. I stumbled into the problem while trying to locate severely outdated DaCHS installations – so, I a way I put effort into the Note Mark was talking about (and which I have just uploaded to the IVOA Document Repository) as a sort of penance.

  While I was already asleep when Mark gave his talk, I was back at the Interop Friday morning CEST, when Hendrik Heinl talked about the LOFAR TAP service (which, I'm proud to say, runs on top of DaCHS); this was mainly live operations in TOPCAT (which is why there's no exciting slides), but Hendrik used a pyVO script doing cutouts in an (optical) mosaic of the Fornax cluster built on top of – and that's the main point – Datalink and SODA. Working this out with Hendrik made me realise the documentation of Datalink in pyVO really needs… love. Or, better, work.

  Later on Friday, there was the Registry session, where I gave brief (and somewhat cramped) talks on advanced column metadata (which is intended to one day let you query the registry for things like “roughly complete to 18 mag” or “having objects out to redshift 4“) and how to put VODataService 1.2 coverage into RegTAP – I expect you'll read more on both topics on this blog as they mature to a level at which this can leave the Registry nerd circles.

  And now, about 10 pm on Friday, the meeting is slowly winding down; beyond all the talks (which were, regrettably for a free software spirit like me, on zoom), the real bonus was that there was a gather.town attached to the conference. Now, that's a closed, proprietary, non-self-hostable platform, too, and so I have all reason to grumble. But: for the first time since February 2020 it felt like a conference, with the most useful action happening outside of the lecture halls, from trying to reach consensus on VEP-006 to teaching DaCHS datalink service declaration to learning about working with visibilities coming from VLBI (where it's even more difficult than it is with the big antenna arrays). So… this one time I've made my peace with proprietary platforms.

  A propos of “say no to platforms“ (in this case, slack): Due to the recent troubles with freenode, in addition to the Interop last week saw the the GAVO IRC channel move to libera.chat (where it's still #gavo). So, for instant messaging us now that the Interop is (in effect) over: Come there.

• Sofa instead of Granada

  2020-11-23 Markus Demleitner

  

  Gesticulating wildly to a computer is what happens in an online conference. To me, at least. Let's hope nobody watched me through the window.

  It was already in the wee hours of Friday last week (CET) when the second "virtual Interop" had its rather unceremonious closing ceremony. Its predecessor in May had about it an air of a state of emergency. For instance, all sessions were monothematic. That was nice on the one hand, because a relatively large part of the time was available for discussion – which, really, is what the Interops are about. But then Interops are also about noticing what everyone else in the Virtual Observatory is cooking up, for which the short-ish talks we usually have at Interops work really well.

  In contrast to that first Corona Interop, this second one, replacing what would have taken place in Granada, Spain, had a much more conventional format, which again accomodated many talks. But of course, this made one feel the lack of possibilities to quickly hash out a problem during a coffee break or in a spontaneous splinter quite a bit more.

  Be that as it may, I would like to give you some insights on what I'm currently up to at the IVOA level; I am grateful for any feedback you can give on any of these topics.

  Given that I currently chair the Semantics Working group, there was a natural focus on topics around vocabularies, and I gave two talks in that department. The one in DAL (DAL is the working group that builds the actual access protocols such as TAP or SIAP) was mainly on Datalink-related aspects of my Vocabularies in the VO 2 draft (VocInVO2), which in particular was an opportunity to thank everyone involved in the Vocabulary Enhancement Proposals we have been running this last year (all of which were about Datalink and hence closely tied to DAL). One thing I was asking for was reviews on a github pull request that would make the bysemantics method of Datalink accesses semantics-aware; basically, as intended by the original Datalink authors, when asking for #calibration links, this will also return, say, #bias links. If you can spare a moment for this: Please do!

  Another thing I tried to raise some interest for is the proposed vocabulary of product types; this, I think, should eventually define what people may put into the dataproduct_type column of Obscore results, and there are related uses in Datalink and, believe it or not, the registration of SSAP (spectral) services. A question Alberto raised while I was discussing that made me realise I forgot to mention another vocabularies-related development relevant for DAL: I've put the gavo_vocmatch ADQL user-defined function into DaCHS. It lets you match something against a term or its narrower terms, referencing an IVOA vocabulary. For instance, if we had different sorts of time series (which, of course, would be odd for obscore that has the o_ucd column for this kind of thing), you could, using ADQL, still get all time series by querying:

  SELECT TOP 5 *
  FROM ivoa.obscore
  WHERE
    1=gavo_vocmatch(
      ’product-type’,
      ’timeseries’,
      dataproduct_type)
  

  Here, the first argument is the vocabulary name (whatever is after the http://www.ivoa.net/rdf in the vocabulary URL), the second the “root” term, and the third the column to match against. Since postgres, for now, isn't aware of IVOA vocabularies, the second argument must be a literal string rather than, say, an expression involving columns.

  I gave a second semantics-related talk in the Registry session. That had its focus on the Unified Astronomy Thesaurus (UAT), from which people should pick the subject keywords in the VO Registry (actually, they should pick from its representation at http://www.ivoa.net/rdf/uat). I'll probably blog about that a little more some other time. For now, let me recommend a little UAT-based game on my Semantics Based Registry Browser sembarebro: Choose two terms that are pretty far apart (like, perhaps, ionized-coma-gases and cosmic-background-radiation) and then try to join the two sub-graphs. Warning: This may waste your time. But it will acquaint you with the UAT, which may be a good thing.

  In that second talk, I also mentioned a second draft vocabulary I've put up in the past six months, http://www.ivoa.net/rdf/messenger. This builds upon the terms for VODataService's waveband element, which enumerated certain flavours of photons (like Radio, Optical, or X-ray). Now that we explore other messengers as well and have more and more solar system resources in the Registry, I'm arguing we ought to open up things by making “Photon” explicit in there and then adding Neutrinos and, later, other messengers. I've received a certain amount of pushback there on mixing the electromagnetic spectrum with particle types; on the other hand, the hierarchical nature of our vocabularies would, I think, let us smartly get away with that.

  Speaking about solar system resources, I'm also listed as an author on Stéphane Erard's talk on EPN-TAP and EPNCore v2.0, probably due to my involvement in finally bringing EPN-TAP into the IVOA document repository. I've already talked about that in a 2017 post on this blog – and again, if you're interested in solar system data, this would be a good time to review the EPN-TAP working draft.

  Talking about things regluar readers of this blog will have heard of: September's Crazy Shapes post I've referenced in a talk on MOCs in pgsphere, together with a fervent appeal to data centers to become involved in pgsphere maintenance.

  And then there was my colleague Margarida's talk on LineTAP, a proposal to obsolete the little-used SLA protocol (which lets people search for spectral lines) with something combining the much more successful VAMDC with our beloved TAP. Me, I'm in this because I'd like to bring TOSS data closer to VAMDC – but also because having competing infrastructures for the same thing sucks.

  And finally, I gave a talk I've called Data Model Posture Review in a session of the Data Models working group; I was somewhat worried that given its rather skeptical outlook it wouldn't be really well-received. But in fact quite a few people shared my main conclusions – and perhaps it was another step towards resolving my decade-old spot of pain: that the VO still doesn't offer tech to reliably bring two catalogues to the same epoch without human intervention.

  With this number of talks I've been involved in, I'm essentially back to the level of a normal Interop. Which means I've been fairly knocked-out on Friday. And I can't lie: I still regret I didn't get to spend a few more warm days in Granada. Corona begone!

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