[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Display types?


At 07:10 PM 3/15/99 +0000, Paul Crowley wrote:
>Ron Rivest <rivest@theory.lcs.mit.edu> writes:
>> I agree with you both the display types are a debatable feature of
>> SPKI/SDSI.  They obviously add a little bit of complexity.  On the
>> other hand, they have the following benefits:
>> 	(1) they allow the use of names over a non-Latin alphabet
>> 	(2) they allow incorporation of pictures and other document
>>             types
>I think these advantages are both important features of SPKI/SDSI, but
>as far as I can tell they can be done without the complexity of
>display types, by adding an entry in the BNF definition for typed data
><printable>: <byte-string> | <mime>
><mime>: "(" "mime" <mime-type> <mime-data> ")"
>or something like this.

If MIME-typed byte strings were always to occur in parameters, this might be 
a valid solution, but as I recall the original debate on this topic, we were 
concerned about letting people use their native character sets for type 
names of sub-expressions (the initial bytestring in an expression).

If we were to go to UTF-8, then that removes the need for MIME types for the 
S-expression type name.  We would allow <printable> only as parameters
in S-expressions, not as type strings.  This allows us to retain the
constraint that the first element of an S-expression is a bytestring.

We started out with UTF-8 as the character set and the discussion on the 
list pushed us back to Latin-1.  I believe the primary objections were from 

If we were to assume UTF-8 for a character set, we also have the problem 
that it's a variable width character set, which means that the byte count
that preceeds a bytestring would not always equal the character count.  This 
would have little effect on a program but might get in the way of a human 
examining the canonical form from a text display.

What is the sense of the group here?

Version: PGP for Personal Privacy 5.5.3


|Carl M. Ellison         cme@acm.org     http://www.pobox.com/~cme |
|    PGP: 08FF BA05 599B 49D2  23C6 6FFD 36BA D342                 |
+--Officer, officer, arrest that man. He's whistling a dirty song.-+

Follow-Ups: References: