Tweak datatype-id property description and annotation. Make `dataty…

[gkellogg]

…pe` an object property. #543.

[JeniT]

The question that remains here is whether we want to allow datatype to reference arbitrary (JSON) datatype definitions which are then retrieved. In other words, should I be able to do:

"datatype": "http://example.org/age"

and have http://example.org/age resolve to the JSON:

{
  "@id": "http://example.org/age",
  "base": "integer",
  "minimum": 0,
  "maximum": 120
}

If so, then we can take out the sentence about the datatype property, if a string, needing to be one of the built-in types, and rely on it being an object property (I think, or do we have to say something about how the strings in that case are mapped onto URLs)?

[gkellogg]

This is a conundrum, and changes much practice. If we have something like the following:

{
  "columns": [{
    "name": "number",
    "datatype": "number"
  }]
}

We can clearly expand the "number" value to a URI using the context, and probably nothing specific needs to be said about this. We probably need to add some rules specific to "datatype" that if the value is a term in the context, it SHOULD NOT be dereferenced (to reduce noise on the network), otherwise, it is expanded to a URL and dereferenced; if the result of dereferencing this is a datatype description, this is used. Otherwise, a new object is created with @id set to that expanded URL.

We want the previous to continue to expand as follows:

{
  "columns": [{
    "name": "number",
    "datatype": {
      "base": "number"
    }
  }]
}

But, if we had something where the value was a URL (not a term in the context, or more specifically one of the datatype terms we define), we could get the following:

{
  "columns": [{
    "name": "number",
    "datatype": {
      "@id": "http://example.org/datatype"
    }
  }]
}

This is one thing that makes this not act like an object property, and this solution is starting to look more involved.

[JeniT]

I think we want

{
  "columns": [{
    "name": "number",
    "datatype": "number"
  }]
}

to expand to

{
  "columns": [{
    "name": "number",
    "datatype": { "@id": "xsd:double" }
  }]
}

which I think is what the object property gives us.

Having said that, the text looks fine from what I can tell.

[JeniT]

@gkellogg would you look over the rewording and see what you think?