VOSpace questions

[Gaudet, Séverin]

Bonjour Grégory

To answer your last question, the CADC has open-sourced the following:

  *   https://github.com/opencadc/cadc-vosui: a portable VOSpace browser
  *   https://github.com/opencadc/vostools: Python command line and FUSE clients
  *   https://github.com/opencadc/vos: Java client and server implementation of the VOSpace specification

Cheers
Séverin

De : <grid-bounces at ivoa.net> au nom de Grégory Mantelet <gregory.mantelet at astro.unistra.fr>
Date : mercredi, 6mai, 2020 à 06:30
À : Grid and Web Services WG <grid at ivoa.net>
Cc : Grégory ADAM <gregory.adam at etu.unistra.fr>
Objet : VOSpace questions

Dear VOSpacers,

With an intern, Grégory Adam, we are starting to look into the VOSpace spec. and we have some (simple, I hope) questions on the document (2.1).

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1. About getNode and its parameter `detail=min`:

    The VOSpace document says:
- min: the returned record for the node contains minimum detail
          with all optional parts removed – the node type should be re-
          turned
    If I try to sum up: the "optional parts" are everything except <vos:nodes> in case of a ContainerNode. So, it means that apart from the node type (attribute xsi:type) a non-ContainerNode will be empty.

    Is it correct?

    If yes, there is a mistake in the example given in 6.3.1: the XML elements <vos:properties>, <vos:accepts>, <vos:provides> and <vos:capabilities> should not be returned. According to the XML schema they are optional.
    Or are they optional only if empty?
    Or because "SHALL" is used instead of "MAY" (in 3.1, page 13) it make them mandatory if not empty?

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2. About getNode and its parameters `uri` and `offset`:

    The VOSpace document says:
If a “uri” and “offset” are specified in the request then the returned list
will consist of the subset of children which begins at the node matching
the specified value of the “uri” parameter and with cardinality matching the
specified value of the “offset” parameter drawn from an ordered sequence
of all children. The ordering is determined by the server but results must
always be drawn from the same ordered sequence.
    When it is said "which begins at the node matching the specified value of the “uri” parameter",
    does "begin" mean "the string begins" or "the returned sublist must starts with"?

    For instance, in the given example:

        http://server.example.com/vospace/nodes/mydir?detail=min&uri=vos://example.com!vospace/mydir/file3401

    * Should the `uri` filter be interpreted as all files whose name begins with "file3401" in the directory "vos://example.com!vospace/mydir"?
       (e.g. "file3401a", "file3401b", ...)

        * If yes, the example in 6.3.1. should be fixed.

    * Or should it be the sublist of all children starting from the child "file3401"?
      (e.g. if the complete ordered list is [file3399, file3400, file3401, file3402, file3403], the returned list would be [file3401, file3402, file3403])

--------------

3. About getNode

    Using the same example as in the document, if I run the following request:

        curl -v "http://server.example.com/vospace/nodes"<http://server.example.com/vospace/nodes>

    Should it give me the list of all child nodes at the root of the VOSpace (as if the root is itself a ContainerNode)?

    Sorry for the possibly stupid question, but it is just to be sure.


--------------

4. About Properties, Capabilities and Views

     Properties, Capabilities and Views may have the following attributes:

        - DisplayName
        - Description
        - UCD (only for Properties)
        - Unit (only for Properties)
        - MimeType (only for Views)

    But none of these elements appear in the XML schema (and they appear in no example). The XML schema does not give enough flexibility to insert additional information like these.

    So, we wonder how to represent them in the XML and where? How can they be discovered?
    Have we missed something?

--------------

5. Existing VOSpace services and clients


    I searched in the VO Registries, but I did not find a lot of (still) active VOSpaces apart from the following ones:

        - ESA (https://vospace.esac.esa.int/vospace/)
        - CADC/Canfar (https://www.canfar.net/storage/list/)

    Are there more?

    Similarly, is there any know (generic) client?

--------------

Thank you in advance for your help.

Cheers,
Grégory


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