Re: [vwrap] The <embed> tag... is the group still interested in LLSD or DSD?

Meadhbh Hamrick <ohmeadhbh@gmail.com> Sat, 07 May 2011 15:19 UTC

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From: Meadhbh Hamrick <ohmeadhbh@gmail.com>
Date: Sat, 7 May 2011 08:19:23 -0700
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To: Joshua Bell <josh@lindenlab.com>
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Subject: Re: [vwrap] The <embed> tag... is the group still interested in LLSD or DSD?
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Josh, it's even worse than that.

Python inherits the integer size from the compiler that generated it.
So, if you compile python on a system with a 16 bit int (which used to
be pretty common in some embedded systems) you get a version of python
that uses 16 bit ints.

I think you touched on an important aspect though... JSON is meant to
be a transfer syntax and is not supposed to make assumptions about the
sizes of types on the sending and receiving system. LLSD is more than
a transfer syntax, it's an abstract type system that DOES impose
limitations on sizes for types. Sometimes it's easy to confuse the
type system with the transfer syntax.

&c &c
m
--
meadhbh hamrick * it's pronounced "maeve"
@OhMeadhbh * http://meadhbh.org/ * OhMeadhbh@gmail.com



On Fri, May 6, 2011 at 9:18 AM, Joshua Bell <josh@lindenlab.com>; wrote:
> On Thu, May 5, 2011 at 11:46 PM, Vaughn Deluca <vaughn.deluca@gmail.com>;
> wrote:
>>
>> What were the reasons to allow onl a single integer type? There must have
>> been a good arguments for that?
>
> IIRC, some of the languages we wished to support (Python comes to mind) did
> not have support for integers larger than 32-bits. ECMAScript doesn't have
> integer number types at all only IEEE 754 64-bit floats; if you constrain
> the input and output to 32-bit integers it can represent those accurately,
> but not 64-bit integers.
> If you look at the history of LLSD, it started with 3 serialization formats
> that explicitly specified the type of values - XML, binary, and "notation" -
> a compact text serialization intermediate in size between binary and XML.
> The IETF drafts dropped notation and added JSON. The JSON serialization was
> "lossy" as LLSD describes types and values that don't exist in JSON
> (Integer, Date, UUID, NaN, Infinity, etc). By design, though, the type
> conversions described in the LLSD Draft accommodate e.g. by serializing a
> Date as an ISO 8601 string, which when interpreted as a date by the receiver
> results in the original Date by the string->date conversion rules. (I don't
> know if we had resolved every issue with JSON serialization; certainly,
> discussion about edge cases on this list never made it into a draft).
> As far as adding new types: I believe there was the belief that this could
> be accommodated by defining an "LLSD2" at some point in the future with a
> distinct MIME type for serializations (e.g. application/llsd2+xml); unlike
> the Web, content negotiation over HTTP was assumed to be functional within
> VWRAP interoperation. Therefore, there was no push to ensure LLSD "v1" was
> internally extensible or comprehensive for all imaginable scalar/structured
> types.
> Anyway... if contributors have implementation of abstract data type systems
> that share characteristics with LLSD and are thinking about adding
> additional scalar/structured types, they should look at the issues with both
> implementation languages and serialization formats.
> -- Josh
>
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