It's for making interoperable APIs, so there is a good motivation for namespaces. But the namespaces are much less intrusive than XML namespaces. Ordinary API consumers don't even have to see them.
One of the key design goals of JSON-LD was that -- unlike its dismal ancestor, RDF/XML -- it should produce APIs that people actually want to use.
But that's not a case of adding namespaces to JSON, is it?
What I mean is if one were to take the skeptical position that JSON is going to end up "re-inventing the XML wheel", that would mean JSON advocates would need to push namespaces into the JSON spec as a core feature of the format. I've never read a discussion of such an idea, but I'd like to if they exist.
Well, yeah, perhaps the craziest thing about XML is that it has namespaces built into its syntax with no realistic model of how or why you would be mashing up different sources of XML tags.
Namespaces are about the semantics of what strings refer to. They belong in a layer with semantics, like JSON-LD, not in the definition of the data transfer format.
I am convinced that nobody would try to add namespaces to JSON itself. Just about everyone can tell how bad an idea that would be.
> Well, yeah, perhaps the craziest thing about XML is that it has namespaces built into its syntax with no realistic model of how or why you would be mashing up different sources of XML tags.
The thing that gets me is that they were added to XML, so the downstream APIs then got mirrored interfaces like createElementNS and setAttributeNS that cause all sorts of subtle problems. With SVG, for example, this generates at least two possible (and common) silent errors-- 1) the author creates the SVG in the wrong namespace, and/or 2) more likely, the author mistakenly sets the attribute in the SVG namespace when it should be created in the default namespace. These errors are made worse by the fact that there is no way to fetch that long SVG namespace string from the DOM window (aside from injecting HTML and querying the result)-- judging from Stackexchange users are manually typing it (often with typos) into their program and generating errors that way, too.
Worse, as someone on this site pointed out, multiple inline SVGs can still have attributes that easily suffer from namespace clashes in the <defs> section. It's almost comical-- the underlying format has a way to prevent nameclashes with multiple attributes inside a single tag that share the same name-- setAttributeNS-- but is no help at all in this area.
