Architecture of Web Application

HTML

Browser (HTML) -> Tomcat (JSP / Struts) -> JDBC/Hibernate -> Database

Browser (HTML) -> Tomcat (JSP / Struts) -> JDBC -> Stored Proc -> Database

Browser (HTML) -> IIS (ASP.NET) -> ODBC -> Database

Browser (HTML) -> Apache Web Server (PHP) -> Database

RIA

Flash Player(swf) -> Remote Object / Web Service -> Application Server (GlassFish) -> Persistence -> Database

Flash Player(swf) -> HTTP Service -> Web Server (Tomcat) -> JDBC -> Database

Silverlight -> HTTP / Other Protocol -> IIS -> Linq / ODBC -> Database

AJJAX

AJAX Framework -> Tomcat/Application Server -> JDBC/Persistence -> Database

Remarks: Those designs could be remixed.

HTTPS (SSL) could apply to the web service.