07/01/10 Web - resources - static content (stored in files) - dynamic content (output of a program/script) - client-server app - clients, e.g. browser, robots/spiders/crawlers, intelligent bots, Web-enabled desktop apps - servers host resources - intermediaries, e.g. proxies - (forward) proxies - reverse proxies (act as both client & server) - user agent: originating client - origin server: ultimate destination HTML URLs - absolute URLs http://www.cs.ucc.ie/dbridge.html http://dgb:paswd@www.cs.ucc.ie:80/dbridge.html - relative URL turned into an absolute URL HTTP - request messages - request line - general headers, e.g. Date - request headers, e.g. User-Agent, e.g. Host - entity headers, e.g. Content-Length - (optional) body - response messages - response line - general headers, e.g. Date - response headers, e.g. Server - entity headers, e.g. Content-Length - (optional) body