Support prefix expansion for URIs about context.orion-ld

[kzangeli]

ok ...
So, "partial alias replacement" for:

• Entity Type Value
• Attribute Names

And (I assume):

• ':' cannot be a part of the name of a prefix
• only one pass

Anything else I need to know?

This doesn't seem too difficult to implement, but the broker will unfortunately be slower ...

And just to make sure I've understood ...
foaf:name in this example will be expanded to http://xmlns.com/foaf/0.1/name

[jmcanterafonseca]

also the object field has to be properly expanded

[jmcanterafonseca]

correct
foaf:name in this example will be expanded to http://xmlns.com/foaf/0.1/name

[kzangeli]

One more doubt here ...
What if I do a GET of an entity created with prefix expansion?

1. GET without context
   What should be returned?
   1.1 Long names (http://xmlns.com/foaf/0.1/name)?
   1.2 Short names (foaf:name) and the context of the entity creation?

2. GET with context (foaf set to http://xmlns.com/foaf/0.2/ inside the context)
   2.1 Long names (http://xmlns.com/foaf/0.2/name)?
   2.2 Short names (foaf:name)? I'd need to return TWO contexts for this ...

The response '2.1' is pretty complex. I'd need to first detect that http://xmlns.com/foaf/0.1/ corresponds to foaf from the context of the creation of the entity. After that I have to do prefix expansion foaf => http://xmlns.com/foaf/0.2/ from the context of the GET request.

[jmcanterafonseca]

1. a GET without @context should return the URI (long names), as you don't have any @context to resolve against

2. If the @context only contains the mapping "foaf": "http://xmlns.com/foaf/0.2/" , as you said you would need to check whether your long URIs contain that prefix, and as you say it can be tricky ... another option is to store for each attribute URI two component parts (prefix, name) or another option is to just return the long URIs and hope for the best that the JSON-LD processor later does the work ...

[jason-fox]

There is another valid case for prefix expansion which is not yet covered:

If I create an entity as shown, with an inline context:

{
    "id": "urn:ngsi-ld:Building:store001",
    "type": "Building",

    "@context": {
	    "type": "@type",
	    "id": "@id",
	    "fiware": "https://uri.fiware.org/ns/datamodels#",
	    "Building": "fiware:Building"
   }
}

I would expect to be able to retrieve it using the FQN https://uri.fiware.org/ns/datamodels#Building. This is a common practice already used within JSON-LD. For example the schema.org JSON-LD context defines the following:

"schema": "http://schema.org/",

"AboutPage": {"@id": "schema:AboutPage"},
"AcceptAction": {"@id": "schema:AcceptAction"},
"Accommodation": {"@id": "schema:Accommodation"},
..etc.

In other words every entity and attribute is defined using the shorthand notation, the FQN is used throughout to alias the shortname. It should just be a matter of preprocessing the context and replacing "xxx:..." if "xxx" has been defined as a FQN previously.