- From: David Ornstein <davido@apocalypse.org>
- Date: Mon, 29 Jan 1996 11:53:33 -0800
- To: "M. Hedlund" <hedlund@best.com>, John Franks <john@math.nwu.edu>
- Cc: www-talk@w3.org
At 10:12 AM 1/29/96 -0800, M. Hedlund wrote: >My recent thinking on this issue is that a form of conditional HTML could >be implemented with <INSERT>. Give some <PARAM>'s that describe the >conditions under which the insert SRC should be requested, and let the >browser decide whether it should get the insert or not. > ><INSERT SRC="http://www.name.dom/path/table.html" > TYPE="text/conditional-html"> ><PARAM NAME="condition" VALUE="vendor-tables/1.1"> ><P>Your browser doesn't recognize vendor-tables/1.1, so you're seeing >this instead.</P> ></INSERT> > >OR logic could be specified by giving more than one PARAM. AND logic >could be specified by recursive INSERTS. Browsers that don't recognize ><INSERT> get the fallback text. Achieving AND and OR this way might (I can't quite get it clear in my head) get in the way of clean (proxy-server) caching. >Advantages: > >* Works in keeping with "the SGML heritage of HTML." > >* Doesn't stuff all possible variants into one document (avoids filesize > bloat). > >* Backwards-compatible. > >* Very cache-friendly (not only can primary docs be cached, so can > <INSERT>s). Good. >* Avoids stuffing browser capability description into huge Accept header. > >Disadvantages: > >* Requires multiple GETs (possibly a good number of them). > >* Requires the browser to parse the <INSERT>s before issuing subsequent > GETs. (Maybe we can get around this with <ALIAS>?) > >The only thing I can say about the first disadvantage is that HTTP is >moving in a direction that will ease the hit of multiple GETs >(Keep-Alive, HTTP-ng). Everything is a tradeoff, but I'll point out that this has a performance-related predisposition towards browsers that don't understart the new construct. Because the fall-back form (<P>Your browser doesn't recognize vendor-tables/1.1, so you're seeing this instead.</P> in the example above) is always sent, browsers that *do* understand the new construct will be, in a sense, penalized by being forced to do the extra GET (and having to have spent extra transport time getting the unneeded fall-back). Of course, this would be the way to maintain backward compatibility, but... ----------------------------------------------------- David Ornstein Outbreak: http://objarts.com/outbreak-unreg BrowserCaps: http://objarts.com/bc Personal Info: http://objarts.com/davido
Received on Monday, 29 January 1996 14:53:51 UTC