Re: Tag Spec

Using `/` for indicating a global tag would go against writing stuff like
`!ruby/sym` (I hesitate to mention this given the latest issues with this
being a security loophole... but anyway).

The current rules were intentionally designed to promote the use of
suffixes. Using !<...> is intentionally ugly. You "should not", in general,
specify full URIs unless under special circumstances. The idea is that you
"should" use suffixes and isolate the full-URI prefixes in there. Whether
or not this intent is "correct", it is what it is.

Getting rid of `!<...>` and replacing it with a rule saying "is a complete
URI if it contains :, is a suffix otherwise" - hmmm. I'm not convinced, but
there might be something in it. Either way, this is be YAML 2 material.

Have fun,

Oren Ben-Kiki

On Sun, Feb 3, 2013 at 9:39 PM, Trans <[email protected]> wrote:

>
> On Sun, Feb 3, 2013 at 1:31 PM, Oren Ben-Kiki <[email protected]>wrote:
>
>> The question isn't one of ease of parsing (we all know YAML isn't easy to
>> parse :-).
>>
>
> :-) Indeed!
>
>  It is a matter of ambiguity. The !<verbatim> syntax was added very late
>> in the game, to allow avoiding the tag prefix games.
>>
>
>>
> The thinking isn't "domain" vs. "local", the thinking is "full arbitrary
>> URI" (inside <...>) vs. "suffix added to some arbitrary URI prefix"
>> (without the <...>). The difference between "!", "!!" and "!foo!" is just
>> "which URI prefix should we use here".
>>
>
> Though in practice that's what people see. Perhaps the better terminology
> is "globally unique" vs "local" tags. Although determining if a prefix is
> applied would depend on whether the tag contains a `:` or not, sticking
> with current spec, !<...> tags would still not resolve. To clarify the
> difference:
>
>     %TAG ! tag:foo.org/
>     ---
>     - !foo                   => !<tag:foo.org/foo>
>     - !tag:bar.org/bar   => !<tag:bar.org/bar>
>
> Also, I think this would open up `!<foo>` to be a legal local tag, rather
> then the degenerate global tag it is now b/c it is not a valid URI. So,
> without a `%TAG !` directive:
>
>     ---
>     - !foo                 => !<foo>
>
> So the `!` would no longer have any significance if a tags *name*. It
> would be used only to designate a tag and to sub prefixes, but a local tag
> would not need to be `!foo` any more, just `foo`.
>
> If we said "we don't attach any prefix if what follows the "!" looks like
>> a complete URI" we'd be entering a world of pain. URIs can be in all sort
>> of forms: "urn:isbn:0-395-36341-1" is a URI and hence (if someone
>> wanted) !<urn:isbn:0-395-36341-1> would be a valid (if somewhat insane)
>> tag. So "looking like a complete URI" isn't really easy to define. "Looking
>> like a tag URI" is well-defined, but YAML really doesn't insist on using
>> "tag URIs", even though we call the "node type tags", well, tags.
>>
>
> I'm not seeing how this translates into be a world of pain. Keeping it
> simple, as in "does it contain a `:`" should suffice b/c `:` is required of
> a valid URI. Local tags can live without them. Some adjustment might be
> required by end users in rare cases. Like your example, they could use !<
> urn:isbn#0-395-36341-1>. I don't think it's too much to ask of end-users
> that local tags not use `:`. (If it really is too much to ask then perhaps
> a different escape notion could be allowed, e.g `![urn:isbn:0-395-36341-1
> ]`.
>
> (Note, before I suggested that `/` be an indicator of global tag too. In
> that case if no `:` is present, `tag:` would be assumed. That just seemed
> like a nice convenience, but it is not necessary.)
>
>

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