Re: Yayson (proposal for a YAML presentation embedded within JSON for browser clients)

Ingy dot Net wrote:

>     It is not clear how you add a tag or anchor to a non-quoted object
>     such as a number, however. Perhaps it is ok if quotes are required,
>     or maybe I'm missing something.
> 
> 
> This is an interesting question. My take is that tagging is only applied 
> to strings. Since each and every tag is resolved by a function, it seems 
> a fair assumption to make.
> 
> I realize that there is a distinction in YAML betwixt:
> 
> ---
> - !foo "3"
> - !foo 3
> 
> But I don't see a constructor making use of that distinction.
> 
> What do you think?

It seems ok. Certainly whether a string is quoted or not is used by YAML 
parsers to determine type, but that is only when the tag is missing. I 
think if there is a tag then it is ok if the value is always quoted. It 
does mean that you cannot add more keywords than JSON supports as 
unquoted constants to YAML but I don't think that is being allowed anyway?

> We need to support a top level '%TAG' and '%JSYNC' syntax:
> 
> %YAML 1.2
> %TAG ! tag:xyz.com <http://xyz.com>,2010:
> %TAG !abc! tag:abc.net <http://abc.net>,2010:
> --- !thing
> this: !abc!widget [2, 4]
> 
> Here is my strawman...
> 
> There are two kinds of top level in JSYNC: map and sequence. Map seems 
> easier:
> 
> {
>   "%": "JSYNC 1.0\nTAG ! tag:xyz.com <http://xyz.com>,2010:\nTAG !abc! 
> tag:abc.net <http://abc.net>,2010:",
>   "!": "thing",
>   "this": ["!abc!widget", 2, 4]
> }
> 
> Here is a similar doc as a top level sequence:
> 
> [
>   "%JSYNC 1.0\n%TAG ! tag:xyz.com <http://xyz.com>,2010:\n%TAG !abc! 
> tag:abc.net <http://abc.net>,2010:\n!thing",
>   ["!abc!widget", 2, 4]
> ]

I would put each '%' into it's own item.

I think of YAML, if you include the "---" dividers, as having a 
top-level list naturally. So perhaps the conversion of YAML to JSON is 
to turn it always into a list. Back-conversion will turn that top-level 
list into --- divided items.

> Good starting list. I would want to escape <SPACE>, !, #, $, %, & 
> because then you could tell a JSON encoder to sort mapping keys (if the 
> option is available) and always get the JSYNC fields at the top of the 
> mapping. Not only is this better visually; it might be _necessary_ if we 
> wanted to do streaming JSYNC libraries.

Okay we have the following list, imho:

DEFINATELY NEED QUOTING:
   !, #, %, &, *

MAY NEED QUOTING:
   @ (reserved for future use by YAML)
   space (I'm not sure why)
   " and ' (also used by YAML at the start of values)

NOT QUOTED:
   +, -, 0-9 (for numbers)
   A-Z, a-z, _ (valid identifiers in most languages)
   All Unicode > 0x7f (match the letters, no UTF-8 decoding needed)
   / and \ (for . and .. filenames)
   "nothing": a string of only periods is unchanged (for . and .. filenames)

UNKNOWN (but I would say not quoted):
   C0 control characters such as newline
   $, (, ), comma, -, :, ;, <, =, >, ?, [, ], ^, `, {, |, }, ~




> 
> As an aside, I think there is about a year of time where you can declare 
> new technology like JSYNC to be alpha, and subject to 
> non-backwards-compatible change. I personally think it is healthy, and 
> avoids things like mandatory tabs in Makefiles!
> 
> 
>      > I have updated the http://jsync.org example to reflect this.
> 
>     This is great and if this question comes up again people should be
>     directed to this web site. Name & syntax are chosen.
> 
> 
> Thanks!
> 
> The next steps are to write up a syntax spec, then an API spec, then 
> create an implementation or two, then write an implementation guide.
> 
> Cheers, Ingy

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