jeff-zucker/solid-file-client

".meta" Implementation Status

Opened this issue · 4 comments

FilippoScaramuzza commented

".meta" Implementation Status

The aim of this issue is for me to understand what is the status of the implementation of metadata ".meta" files both in the Solid Specification and in solid-file-client library.

ldp:Containers

As far as I understood, ldp:Containers are linked with .meta files, which content is shown for example when requesting (GET) on a Container. To get the link to the specific .meta file, it should be sufficient to inspect the Link Header in the response as written in [https://github.com/solid/solid-spec/blob/master/content-representation.md#metadata][https://github.com/solid/solid-spec/blob/master/content-representation.md#metadata].

This works, and I am able to see the .meta file in the response header, for example a get on public/ gives:

Link: <.acl>; rel="acl", <.meta>; rel="describedBy", <http://www.w3.org/ns/ldp#Container>; rel="type", <http://www.w3.org/ns/ldp#BasicContainer>; rel="type"

Now, if I try to access the .meta on public/.meta file directly I get:

Can't find file requested: [object Object]

ldp:Resources

As far as I can see, for ldp:Resources should be the same thing, for example a GET on public/test.txt returns:

Link: <img.png.acl>; rel="acl", <img.png.meta>; rel="describedBy", <http://www.w3.org/ns/ldp#Resource>; rel="type"

Nonetheless, the behaviour is the same, a request to img.png.meta gives 404.

Direct Access to .meta

Reading .meta files seems impossible, and I suppose is because they're not created yet. So I tried to create one (img.png.meta), but I got:

Error SFCFetchError: SFCFetchError 415 https://pimsfsc.solidcommunity.net/public/img.png.meta
    at assertResponseOk (webpack://SolidFileClient/./src/utils/errorUtils.js:93:11)
    at processTicksAndRejections (node:internal/process/task_queues:96:5)
    at async writeFileContent (/home/admindin/PIMS.FSC/Experiment.TestSolidServerNode/src/app.ts:109:9)
    at async mainMenu (/home/admindin/PIMS.FSC/Experiment.TestSolidServerNode/src/app.ts:39:13)
Error SFCFetchError
Error SFCFetchError 415 https://pimsfsc.solidcommunity.net/public/img.png.meta

I tried both with a simple payload like test and with an RDF formatted content, but nothing: same error.

Is this because one cannot directly modify .meta files? What about RDF description of non-rdf resources, shouldn't it be exactly in .meta files?

Final Questions

  1. How can I directly read .meta files?
  2. Can I create .meta files?
  3. Can I do the same for both ldp:Containers and ldp:Resources?
  4. What is the correct way to descirbe non-rdf resources?

Thank you,
FS

bourgeoa commented

@FilippoScaramuzza
thanks for your questions :

  1. to read the /.meta content you can either :
  2. to create .meta file. Browser creation with the solidOS webApp is not possible SolidOS/source-pane#55. You need to use fetch directly or through a package like solid-file-client.
    • .meta can be created on container : containerName/.meta, or any document resources example img.png.meta
    • .meta are of contentType text/turtle. They must have a content representation of text/turtle
  3. yes see 2.
  4. do you want to have metadata has non rdf resources ? Then nothing is in solid
FilippoScaramuzza commented

Hello @bourgeoa, thanks for the prompt reply.

1/2/3:
I wrote a simple script using solid-file-client to write any arbitrary file at any arbitrary localtion. Anyway, the result is the following (note that the first tree lines are my program's output):

Write the file path of the file you want to upload: ~/Desktop/test.ttl
Write the resource expected location (e.g. public/example.png): public/img.png.meta
... uploading text/turtle; charset=utf-8 file ...

Error SFCFetchError: SFCFetchError 415 https://pimsfsc.solidcommunity.net/public/img.png.meta
    at assertResponseOk (webpack://SolidFileClient/./src/utils/errorUtils.js:93:11)
    at processTicksAndRejections (node:internal/process/task_queues:96:5)
    at async writeArbitraryBinary (/home/admindin/PIMS.FSC/Experiment.TestSolidServerNode/src/app.ts:136:9)
    at async mainMenu (/home/admindin/PIMS.FSC/Experiment.TestSolidServerNode/src/app.ts:42:13)
Error SFCFetchError
Error SFCFetchError 415 https://pimsfsc.solidcommunity.net/public/img.png.meta

I know 415 Error should be 415 Unsupported Media Type, so I made sure to upload it with the right content type as you suggested, but still the same problem.
Do you think there's something I am missing? As far as I understood it should be the same process of creating standard files, but with a check on the content type to be text/turtle. So I don't know what I am doing wrong.

4:
My apologies, I think there is a misanderstanding: I would like to write rdf metadata for non-rdf resources. I was asking that because since I'm having problems in creating .meta files I thought that the solid implementation I am using was somehow not adherent to the spec.

bourgeoa commented

@FilippoScaramuzza
I did continue my research and it appears that until now (NSS@v5.7.8 the current https://solidcommunity.net implementation .meta are only allowed on container resources.
I think to remember (?) that the spec issue was with .meta.acl on document resources.

CSS allow to use .meta on document resource but not .meta.acl.

jeff-zucker commented

If the container /photos/ has a file /photos/image.png, then you can say in /photos/.meta <./image.png> rdfs:label "my pretty picture". and then when you do a GET on /photos/ the label will be available there.