Unicode Explained

Types of Negotiation

Although we have concentrated on language negotiation, similar mechanisms work for

other types of content negotiation, though normally without using user preferences:

Media type negotiation

You can make the same information available, for example, as plain text, in PDF

format, and in HTML format. You could then use the type‑map mechanism of

Apache for language negotiation, and use different Content-Type headers. The

browser is expected to list its media type preferences in an Accept header. This is

not very useful in most cases, since browsers often express such preferences in a

manner that contains too little information or cannot be trusted in practice.

Encoding negotiation

Similarly, you can make the same information available in different character en-

codings. Using the type-map mechanism for example, the Content-Type headers in

your definition file would contain charset parameters that indicate the encoding

of each version. The browser is expected to list its encoding preferences in an

Accept-Charset header. However, many popular browsers do not send such a

header at all, which means that they accept any encoding.

Transfer encoding negotiation

Additional transfer encoding (see Chapter 6) can be agreed upon between the

browser and the server. A browser uses Accept-Encoding to specify the transfer

encodings it can handle. Figure 10-9 shows