2nd June, 2021

Attendees: Josh, Ward, Jackson, Hailey, Dennis, John

Introductions
Community items?
- Papers & benchmarks (aicsimageio!)
- OME meeting: “did you think of zarr”
- Messaging (and all the papers). EOSS money?
- Conferences in the Winter season: AGU,
  
  EGU, …
  - Talking about NetCDF & Zarr. Good chance to coordinate.
  - Very large, 25K attendees! “Earth science” incl. a lifescience component
  - Ward to bring it back to our attention when proposals are open.
  - “Earth and space science informatics” section. Daily posters.
  - “Technologies as they apply to a domain” (10+5)
  - Also cross-discipline sessions.
Core
- Josh (Py): Dependabot & Python 3.6
  - John: dropped in xarray, dask, tifffile, numpy
  - Josh to open an issue
  - https://github.com/zarr-developers/governance/issues/11
  - https://github.com/zarr-developers/community/issues
- Josh (Py): Review backlog
  - e.g. Azure
  - “Mutable mapping from all cloud providers” ❤️
  - Use of owners?
  - https://github.blog/2017-07-06-introducing-code-owners/
  - via blame … separate files.
  - https://github.com/zarr-developers/zarr-python/pull/759 → storage into a package and then separate files.
  - Start with an issue? → https://github.com/zarr-developers/zarr-python/issues/764
- Dennis (C)
  - How proposing to handle numcodec in nczarr. https://github.com/zarr-developers/zarr-specs/issues/41#issue comment-848222877
  - Also how to store structs? https://github.com/zarr-developers/zarr-specs/issues/118
    - https://github.com/saalfeldlab/n5/pull/73#issuecomment-688731487
    - Dennis: in HDF5 you can specify the padding. In python
      
      is all tightly packed? (Would prefer to stick with tightly packed)
    - John:
      
      https://numpy.org/doc/stable/user/basics.rec.html#automatic-byte-offsets-and-alignment is the definition. Possibly configurable. Would need input to know what is important.
  - Primarily working on filters for netcdf
  - Exposing numcodec API through netcdf (i.e. specifying filter through JSON). Not supported at the moment. Need to use HDF5 mechanism.
    - John: support for categories (e.g. enums) that e an ID.
    - Dennis: use characters (enums) for it.
    - John: testing of various implementations in
      
      https://github.com/zarr-developers/zarr_implementations/tree/master/generate_data
  - Critical to get users is the interoperability with HDF5. A bit stuck.
  - Even more important is xarray/zarr format. (More people are using it)
  - Need maximal interoperability with V2. V3 is on the horizon. (Won’t be there for quite a while)
  - True for Java as well. Will be reading V2 for quite a while.
- Hailey (Java)
  - Agreed. Need v2.
  - Josh: update the spec & get zarr_implementations
  - Dennis: live without structs. filters is important.
  - Josh: so hearing that numcodecs registry is most important? https://github.com/zarr-developers/numcodecs/issues/278
  - Dennis: most critical piece is officially change numcodec representation to optionally include HDF5 ID. → alias field.
Misc
- Josh: h5coro (for Martin) - tabled