RE: [xsl] Ampersand for URLs

Subject: RE: [xsl] Ampersand for URLs
From: "Michael Kay" <mhkay@xxxxxxxxxxxx>
Date: Tue, 24 Apr 2001 09:18:55 +0100
Mike Brown wrote:
> *sigh* Why is this so hard for people to grasp?

Answer: because the specs are such a mess: no-one would have ever designed
it this way, it just grew.

> You can also use %, but only to indicate the beginning of an escape
> sequence of the form %XX where XX are 2 characters that form a
> hexadecimal number from 00 to, theoretically, FF, although
> the meaning of
> anything above 7F (the upper limit of ASCII) is questionable.

The meaning of characters above 7F is very clear, I think. If you want to
use non-ASCII characters in a URI, for example if you have a query parameter
whose value is the name of a person who doesn't happen to have a good old
English name like Brown or Kay, then the spec says that you must encode the
non-ASCII characters in UTF-8 and encode each of the resulting bytes in the
form %HH. This will ALWAYS give you bytes in the range 80 to FF.

("The spec" here is the HTML spec: as far as I'm aware this escaping scheme
is defined only for use in HTML, though I gather it's likely to become an
Internet RFC in due course).
> The reason you would want to use a %XX escape sequence is so you can
>   (1) represent a reserved character being used for something other than
>     its reserved purpose
>   (2) represent the other ASCII characters that exist but that
> are disallowed
>     in URIs, like %20 for the space character, %22 for the
> double quote, etc.

add (3): represent a non-ASCII character in a URI.

Mike Kay

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