@type as @container:@set?

[gkellogg]

The purpose of the @container:@set functionality (AFAIU) is to ensure that the output is consistent in shape. Thus if there can ever be multiple values, the structure is always an array.

There are two situations in which this functionality could be desirable but is currently not possible:

1. @type As it's a keyword, we can only alias it (e.g. as type) but not define it to have @container:@set functionality. Meaning that there's a gotcha waiting to happen for ontologies that require or use multiple classes for a single resource instance. See playground
2. @context Less useful, but @context will also compact to a single string/object when there might be multiple contexts. See playground

@context modifying itself seems particularly strange, but the inconsistency for @type seems solvable if the restrictions in its definition were loosened?

Original issue @type as @container:@set? #512.

(Edit: Note that the playground links demonstrate that these do not work as one might expect, due to the keyword definitions of @type and @context)

[dlongley]

Seems like a useful feature to allow @container: @set for @type.

[gkellogg]

We should consider allowing any keyword that can take multiple values, such as @graph, to allow it's container model to be updated. A use case outlined in #30 (comment) would do the following:

{
  "@context": {
    "dataset": {"@id": "@graph", "@container": ["@graph", "@id"]}
  },

It should allow the following as well:

{
  "@context": {
    "@graph": {"@container": ["@graph", "@id"]}
  },

This may need some extra sanity checking, as @list, or anything not including @graph would be prohibited.

[azaroth42]

Resolution on WG call of 2018-08-17: @type (or an alias of it) can be set to be a @container (only), and if so it can have only the value of @set. This allows the use case of requiring the field to always be an array for consistency, even if there's only one value.

And secondly, that we will not change @context as the processing would be extremely convoluted for minimal value.

[azaroth42]

Interestingly, someone proposed this be allowed back in 2012: json-ld/json-ld.org#80 (comment) 😀