recently, microsoft tries to attack adobe's dominating Portable Document Format (PDF) with its own version of a print format, called XML Paper Specification (XPS). this obviously is a dumb name, but most people will never know what the full name is anyway.
after installing the XPS viewer and locating an XPS document on the web (which is not too easy, XPS currently is not very popular), you see something that looks like a very stripped down version of the acrobat reader. less features, but this could be a good thing given the feature creep that has turned acrobat into the bloatware that it is today.
it is interesting to look at what browsers send as HTTP Accept header field, and how much that is influenced by PDF or XPS. for the browsers i have on my computer, here are the Accept headers they are sending:
- Firefox:
text/xml, application/xml, application/xhtml+xml, text/html;q=0.9, text/plain;q=0.8, image/png, */*;q=0.5 - Opera:
text/html, application/xml;q=0.9, application/xhtml+xml, image/png, image/jpeg, image/gif, image/x-xbitmap, */*;q=0.1 - Safari:
text/xml, application/xml, application/xhtml+xml, text/html;q=0.9, text/plain;q=0.8, image/png, */*;q=0.5 - IE:
image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, application/xaml+xml, application/vnd.ms-xpsdocument, application/x-ms-xbap, application/x-ms-application, */*
as you would expect, IE's Accept header is terribly broken, technically speaking IE does not even explicitly request HTML from a web server... this is probably one of these things they broke in early IE releases and now they are afraid to fix it because then broken servers relying on their broken browser could stop working the broken way they worked before...
so apart from all the problems with their HTTP, microsoft at least has realized that there are MIME types. adobe is even better, there is a standard for the application/pdf MIME type, but it does not show up in the browser request. the MIME type registry lists the application/vnd.ms-xpsdocument type, but there is no official registration for it.
if publishers set up servers in a way that they can serve print-quality documents in either PDF or XPS, then it will depend on the browser configuration what users will get. currently, users will get the server's default with the exception of IE, which will probably get XPS (even though it did not have to, because they do not properly set the quality factor, so */* is as relevant as application/vnd.ms-xpsdocument).
so this could turn into some kind of fight over who gets his MIME type into the HTTP header with the higher quality factor, similar to the applications which upon installation take over all kinds of file name extensions.
but in the end, maybe there will not be too many servers serving both PDF and XPS and negotiating that with the browser, and the Accept header will remain a mostly obscure piece of information that most servers simply ignore.
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