Artikel mit Tag Semantics:

  • DaCHS 2.5: Check your UCDs

    DaCHS logo on top of a map of UCDs

    In the background of the DaCHS 2.5 release picture: UCDs grabbed from the Registry. The factual background: DaCHS 2.5 will now moan at you when you invent or mistype UCDs

    This afternoon, I have released DaCHS 2.5. As usual, I will discuss the more important changes in a blog post – this one.

    A change many of you will not like too much is that DaCHS now validates UCDs you give it, and it will warn you when you do not follow the UCD rules. This may seem like nit-picking, but as blind discovery is on the verge of becoming usable in the VO, making sure these strings actually are what they should be is becoming operationally important: If I want to find resources that give errors for their photometry, I have to know whether it's stat.error;phot.mag.b or phot.mag.b;stat.error, or else I will miss half the resources out there.

    So, I'm sorry if DaCHS starts complaining about half of your RDs after you update, but it's for a good cause. And don't feel bad about the complaints: DaCHS complained about close to half of my RDs after I had put in that feature.

    By the way, this comes as part of a larger effort on the side of the Operations IG to improve the validity of UCDs and units in the VO, an effort that has unearthed bugs in the SSAP and SLAP specifications in that they require UCDs forbidden by the UCD standard. DaCHS 2.5 still follows SSAP and SLAP, and hence external tools like stilts will protest because of bad UCDs even if DaCHS is happy. Errata for the specifications are being worked on, and once they are accepted, DaCHS and stilts will finally agree on UCD validity, or so I hope.

    Code-wise, a much more intrusive change was that asynchronous services (in particular, async TAP) now use the same formalism for parsing parameters as their synchronous counterparts. It may seem odd that that hasn't been the case up to now, but there were good reasons for that; for instance, with async, people can post incomplete parameter sets that would be rejected by normal sync processing.

    Unless you are running User UWS services, you should not notice anything. If you do run User UWS services, please contact me before upgrading. I would like to work with you on how these should look like in the future.

    Another change that might break your services is that DaCHS now actually complies to VOUnits, which has always forbidden whitespace of all kinds in unit strings. DaCHS, on the other hand, has foolishly encouraged putting whitespace between scale factors and pure units, as in 1e-10 m. That's not interoperable, and hence DaCHS now rejects such units. This may lead to hidden failures when dachs val doesn't notice something is a unit, and things only break during execution. I'm aware of one place where that's relevant: spectral cutout services that need to know the spectral unit If you're running those, make double sure that the spectralUnit in the SSAP mixin does not contain any whitespace. It's 0.1nm according to VOUnits, not 0.1 nm.

    An update that should silently make your services more compliant is that DaCHS' representation of EPN-TAP is updated to what is currently under IVOA review. After you upgrade, DaCHS will try to update your EPN tables' metadata, which in turn should make stilts taplint a lot happier. It will also make DaCHS pass on the new, IVOA table utype to the Registry, which is how people should in the future find EPN-TAP data.

    DaCHS now also contains some code that may help you import data from HDF5 files. For one, there is the HDF5 grammar, which rather directly pulls data from HDF5s written by astropy or vaex. But, really: HDF5 is a rather low-level format not particularly well suited for relational data, and it is virtually impossible to write generic code for doing something sensible with it. The two flavours DaCHS supports have very little in common, and it is therefore almost certain that if you have HDF5s coming from somewhere else, hdf5Grammar will not understand them. Still, let us know what you've got, we may be able to put support for it in.

    Hdf5grammar is written in Python, and thus imports perhaps a few thousand rows per second. For Gigarow-sized data collections, that's nowhere near fast enough, and hence for vaex-written HDF5s, there is booster support. As before, if you have bulk data in HDF5 that you want to put into a database and that was not written by vaex, let us know and we'll see what we can do.

    A surprisingly minor change enabled DaCHS to deal with materialised views, database views that are turned into actual tables by postgres. See the corresponding section in the tutorial for how you can use them. We do not have any materialised views in our Heidelberg data center yet. So, if you use them and notice something is clunky, your feedback is particularly appreciated.

    There are many smaller changes and improvements; let me mention what the changelog euphemistically calls ”better systemd integration”, which really means that so far systemctl restart dachs simply didn't do anything at all. Apologies. And shame on everyone who was bewildered but failed to report this to dachs-support.

    Also, you can use float arrays in boosters now, and DaCHS' ADQL has just leared about COALESCE. That's a SQL feature that lets you deal sensibly with NULLs in some cases: COALESCE(arg1, arg2, ...) will return the first non-NULL argument it encounters. That may sound like a slightly exotic function. Until you need it, at which point you wonder how ADQL could reach its ripe age without COALESCE.

    Finally, let me mention something that is not part of the release, though it is DaCHS-related and is new since the last release: I have cleaned up the access log processing machinery we have used in Heidelberg in the past 15 years or so, and I have packaged it up for general consumption. It is, of course, a DaCHS RD that you can just check out and use in your own DaCHS installation if you have to keep access logs and want to do that with at least some basic respect for your user's rights. See http://docs.g-vo.org/DaCHS/tutorial.html#access-logs for details.

  • The 2021 Southern Spring Interop

    A Venn diagram of product types that just doesn't work.

    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

    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.

  • Semantics, Cross-Discipline Discovery, and Down-To-Earth Code

    Boxes-and-arrows view of the UAT

    A tiny piece of the Unified Astronomy Thesaurus as viewed by Sembarebro – the IVOA logos sit on terms that have VO resoures on them.

    Sometimes people ask me (in particular when I'm wearing my hat as the current chair of the IVOA Semantics working group) “well, what's this semantics thing good for?“ There are many answers, but here's one that nicely meshes with my pet subject data discovery: You want hierarchical, agreed-upon word lists to bridge discipline gaps.

    This story starts with B2FIND, a cross-disciplinary metadata aggregator for science data run within the framework of the European Open Science Cloud (EOSC). GAVO (or, more precisely, Heidelberg University's Astronomy) is involved in the EOSC via the ESCAPE project, and so I have had the pleasure of interacting with B2FIND for a while now. In particular, they are harvesting the metadata records of the Virtual Observatory Registry from us.

    This of course requires a bit of mapping, because the VO's metadata formats (VOResource, VODataService, and several extensions; see 2014A&C.....7..101D to learn more) are far too fine-grained for the wider scientific public. Not even our good friends from high-energy physics would appreciate being served links to, say, TAP endpoints (yet!). So, on our end we're mapping to the Datacite metadata kernel, which from VOResource is just a piece of XSL away (plus some perhaps debatable conventions).

    But there's more to this mapping, such as vocabularies of subject keywords. You might argue that in the age of rapid full text searches, keywords are dead. I would beg to disagree. For example, with good, hierarchical keyword systems you can, among many other useful things, offer topical browsing of metadata repositories. While it might not quite qualify as “useful” yet, the SemBaReBro registry browser I've hacked together late last year would be an example for such facilities – and might become part of our WIRR Registry searching tool one day.

    On the topic of subject keywords VOResource says that resources in the VO should be using the Unified Astronomy Thesaurus, specifically in its IVOA incarnation (not quite true yet, but true enough by blog standards). While few do, I've done a mapping of existing keywords in the VO to UAT concepts, which is what's behind SemBaReBro. So: most VO resources now have UAT concepts.

    However, these include concepts like AM Canum Venaticorum Stars, which outside of rather specialised circles of astronomers few people will ever have heard about (which, don't get me wrong, I personally regret – they're funky star systems). Hence, B2FIND does not bother with those.

    When we discussed the subject mapping for B2FIND, we thought using the UAT's top-level concepts might be a good start. However, at that point no VO resources at all actually used these, and, indeed, within astronomy that generally wouldn't make a lot of sense, because they are to unspecific to help much within the discipline. I postponed and then forgot about the problem – when the keywords of the resources weren't even from UAT, solving the granularity mismatch just wasn't humanly possible.

    That was the state of affairs until last Tuesday, when I had a mumble session with B2FIND folks and the topic came up again. And now, thanks partly to the new desise format proposed in the current Vocabularies in the VO 2 draft, things fell nicely into place: Hey, I have UAT concepts, and mapping these to the top-level terms isn't hard either any more.

    So, B2FIND gets the toplevel keywords they've been expecting all the time starting today. Yes: This isn't a panacea suddenly solving all the problems of cross-discipline data discovery, not the least because it's harder than one might think to imagine how such a thing would look like in practice. But given the complexities involved I was positively surprised how easy this particular part of the equation was.

    From here on, there's a bit of tech babble I intend to re-use in the RFC of Vocabularies in the VO 2; don't feel bad if you skip it.

    The first step was to make the mapping from UAT terms to the toplevel terms. The interesting part of the source I'm linking to here is:

    def get_roots_for(term, uat_terms):
      roots, seen = set(), set()
    
      def follow(t):
        wider = uat_terms[t]["wider"]
        if not wider:
          if not t in ROOT_TERMS:
            raise Exception(
              f"{t} found as a top-level term")
          roots.add(t)
        else:
          seen.add(t)
          for wider in uat_terms[t]["wider"]:
            follow(wider)
    
      follow(term)
      return roots
    

    There, uat_terms is essentially just a json-decode of what you get from the vocabulary URI if you ask for desise (see the draft spec linked to above for the technicalities). That's really it, and it even defends against cycles in the concept graph (which are legal by SKOS but shouldn't happen in the UAT) and detached terms (i.e., ones that are not rooted in the top-level terms). For what it does, I claim that's remarkably compact code.

    Once I had that, I needed to get the UAT-mapped subject keywords for the records I'm serving to datacite and fiddle the corresponding roots back in. That's technically a bit more involved because I am producing the datacite records on the fly from the XML representation for VOResource records that I keep in the database, and there's a bit of namespace magic involved (full code). Plus, the UAT-mapped keywords are only kept in the database, not in the metadata records.

    Still, the core operation here is relatively straightforward. Consider:

    def addUATToplevels(dataciteTree):
      # dataciteTree is an (lxml) ElementTree for the
      # result of the XSL transformation.  That's all
      # I have, and thus I first have to fiddle out
      # the identifier we are talking about
      ivoid =  dataciteTree.xpath(
          "//d:alternateIdentifier["
          "@alternateIdentifierType='ivoid']",
          namespaces={"d": DATACITE_NS}
        )[0].text.lower()
      # The .lower() is necessary because ivoids
      # unfortunately are case-insensitive, and RegTAP
      # normalises them to lowercase to retain sanity.
    
      # Now pull the UAT-mapped subject keywords from
      # our RegTAP extension (getTableConn is
      # DaCHS-internal API, but there's no magic in
      # there, it's just connection pooling with
      # guarantees against connections  idle in
      # transaction).
      with base.getTableConn() as conn:
        subjects = set(r[0] for r in
          conn.query("SELECT uat_concept"
            " FROM rr.subject_uat"
            " WHERE ivoid=%(ivoid)s", locals()))
    
      # This is the mapping itself: we do
      # roots-subjects to avoid adding
      # root terms that are already in
      # the record itself.  UAT_TOPLEVELS is the result
      # of the root finding discussed above.
      for term in subjects:
        root = UAT_TOPLEVELS[term]
        newRoots |= (root-subjects)
    
      # And finally fiddle in any new root terms found
      # into the datacite tree
      if newRoots:
        subjects = dataciteTree.xpath(
          "//d:subjects",
          namespaces={"d": DATACITE_NS})[0]
        for root in newRoots:
          newSubject = etree.SubElement(subjects,
            f"{{{DATACITE_NS}}}subject")
          newSubject.text = root
    

    Apart from the technicalities I'd again say that's pretty satisfying code.

    And these two pieces of code are really all I had to do to map between the vocabularies of different granularities – which I claim will probably be the norm as metadata flows between disciplines.

    It's great to see the pieces of a fairly comples puzzle fall into place like that.

  • Sofa instead of Granada

    Screenshot from an online talk

    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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