Telco 20210505

Date

Wednesday, 5th May, 13:00 UTC

Connect

Agenda

  • Welcome new members

  • Review previous meeting minutes and actions: March Telco

  • Discuss the proposed NeXus ontology, including:

  • Issues on Github labelled with “telco”

Present

BW, SC, HG, MK, PC, AB, HB, PJ, TM, FA, WG

Minutes

The previous TC has been combined with a closeout session of the code camp. BW thanked people for their work and the code camp and in tidying up tickets subsequently.

The main topic for the meeting was to discuss the proposed NeXus ontology. HG had invited SC (Steve Collins, Diamond Light Source) to present some of what they had been working on. The ontology work has been done as part of ExPaNDS task 3.2 to “develop EU photon and neutron ontologies” It aims to standardise metadata in metadata catalogues to use common semantics and also to link to similar or equivalent items in other vocabularies where possible. SC presented a summary of the ideas involved and demonstrated an ontology browser and the python code used to generate the ontology from the NXDL files and markers that had been added to them (the python uses the owlready2 package). It was proposed to host the generating scripts and output ontologies in the nexus github repository. PJ suggested a separate ontology repository, and that the ontology should be tied to an NXDL release (in the owl:versioninfo field).

  • Ontologies can be uploaded to sites such as Bioportal.

  • A PURL (or set of PURLs) provides a persistent name coupled with a (modifiable) URL to point to the location of the OWL ontology file(s).

  • Scripts build the OWL ontology using only the NXDL files as input, aside from a few paragraphs of text that explain the purpose of the document. The ontology can be viewed as just an alternative documentation of NeXus, focused on the semantics, and doesn’t affect how data files should be written, read or interpreted.

  • The ontology itself is a single file with a format similar to XML.

  • We probably want to build an ontology for each major release of NeXus. (And therefore perhaps have a PURL for each.)

  • All present agreed that hosting the files on github doesn’t require a NIAC vote, but the use of the NeXus name in a PURL should go to a NIAC vote. Once the files are properly set up in the new NeXusOntology github repo then we will have something more concrete to base a vote on.

  • PC brought up an issue where the assumption that a beam lies on the Z-axis was problematic and suggested adapting NXbeam to allow description of other geometries.

  • BW brought up the case of accelerator groups wishing to use NeXus, but not having a sample, and suggested thinking about a more general solution to defining the coordinate system.

  • Many facilities use “survey points” to measure the positions of equipment.

Actions

HG, PJ: Use the new NeXusOntology github repo to build a full demonstration of the NeXus ontology project. PC: Investigate ways to define coordinate systems.

Next Meeting

Aim for the beginning of June - poll