Re: [xml-dev] List of differences between XML and JSON?

I think a more rigorous wording would simplify matters. How about the following notions.

XML and JSON are data formats defined in terms of a syntax.

The syntax does not define the information content. This is left to an information model to be applied to the syntax.

XML standards offer two information models: the information set and the XDM. For practical purposes, I think one should only consider the XDM. So an XML document is a tree of nodes, where each node is an entity with a precisely defined list of properties. The information content of a document *is* this tree.

Concerning JSON - is there any standardized information model? The XQuery 3.1 approach of maps and arrays is just one possible information model, not *the* information model. Hence Dimitre's statement that in JSON subtrees can be shared makes (to me) only sense when equating JSON to a particular information model. (Which one? XDM maps/arrays? _javascript_ objects? ???) This can be quite misleading. There is no basis for such a statement in the syntax, just as there is no basis in the XML syntax for excluding the sharing of subtrees. XML might be modelled without nodes, JSON can definitely be modelled with nodes.

I do not believe that there is any substantial difference as to what XML and JSON "is". Both are about instantiating information. More specifically, both are languages for the hierarchical organization of named data. There are different uses for both formats, and it is downright wrong to equate any of the formats with a particular use. So, for example, XML and JSON can be used for information exchange. Both can be used for persisting object data. Etcetera.

My conclusion: in order to avoid confusion, better (a) distinguish clearly between language syntax and information models used to define the information content of syntax instances, (b) distinguish clearly between a data format and the uses it can be put to.

Cheers,

Hans-Juergen

Liam R. E. Quin <liam@w3.org> schrieb am 6:55 Samstag, 2.Mai 2015:

On Sat, 2015-05-02 at 00:20 +0100, Michael Kay wrote:
> >

>
> We've made choices in the way we model XML for processing, for
> example we provide a parent axis so when you are at a node, you can
> find its parent. That's convenient for many kinds of processing, but
> it makes it very hard for two XML trees to share a subtree, which
> makes it expensive to make small modifications to a large tree.

I've used two or three XML (and SGML) editors that didn't work that
way exactly, in order to support entities that remain in place on
export -- with the contents of each entity being shared across
multiple entity references. Serna was one such editor.

The XDM isn't the only possible data model for XML, of course.

> I don't think there's anything in the BNF of XML or JSON that made
> those different design choices inevitable.

Agreed.

Liam

>
> Michael Kay
> Saxonica
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