[Yaml-core] equality and identity (spec finishing touches)

[Clark C. E. <cc...@cl...>]

On Thu, Sep 09, 2004 at 02:35:09AM +0100, David Hopwood wrote:
|  - redefine equality as an operation that can produce three results:
|    equal, unequal, or unknown. The result is unknown iff it depends on
|    computing a canonical value for a scalar node with a tag that is not
|    recognized by the implementation.

I like this change, it will also apply to ?unspecified tags which, by 
definition, are never recognized as they must be resolved.

|    (It is still possible for two scalar nodes with an unrecognized tag
|    to be reported as equal, if they have exactly the same string value.)

Correct.

|    The value of a node includes its kind, so the definition of equality
|    does not depend on each tag being associated with a single kind.

It doesn't hurt to be redundant, no?

|    Remove the definition of identity in 3.2.1.3. Whether nodes are
|    represented by the same native object has nothing to do with the
|    representation model or with equality; it's an implementation detail.

It is there for two reasons:

  - as a contrast to 'equality', with which it is sometimes confused; and

  - to help determine which sorts of objects they should use, if their
    application requires that two 'nodes' with the same string value
    remain distinct, then they should use a collection (such as 
    a sequence with exactly one value).

Given YAML's purpose as a cross-language serialization tool, I think
the latter point is quite important, no?  Perhaps not.  I'm not dead
set against keeping it in.

Cheers,

Clark