In IIS, an application is a defined set of directories of a site. An application must have a starting point directory. In ISM, starting point directories have an icon of an opened package.

All files and directories within the starting point directory are within the application's domain unless a new application is initiated some where within the starting point directory. The default web site is itself an application starting point directory. A site can contain multiple applications.

A directory can be configured to be an application starting point via the Directory tab of the directory's property page. Applications are either created and named or removed.

The Directory tab can also be used to set permissions for the directory. Content directories should have read permissions but not app directories (otherwise users can copy your apps). App directories should also have either script or execute permissions, preferably script.

Applications can be set to run in a process separate from IIS or stopped (if running as separate). Isolated apps are safer since an application failure will not cause server failure.

Once a directory starting point is set. The starting point application configuration can be set. Application configuration includes application mapping. This is where the extensions of files on the system are mapped the appropriate DLL (Dynamic Link Library). EG: All files ending in *.asp, will call up asp.dll; *.idc will call up httpodbc.dll; *.shtm will call up ssinc.dll, and CGI scripts will call up their corresponding script interpreters.

The capabilities of IIS is extended with ISAPI DLLs (Internet Server Application Programming Interfaces) called connectors. These connectors help IIS interface with other services. EG:

  • MS Exchange Server/Web Connector allows public folder integration with MS Exchange Server.
  • IDC (Internet Database Connector) allows communication with ODBC (Open DataBase Connectivity) databases.
  • CGI Connectors (Common Gateway Interface) allows backward compatibility with UNIX CGIs.
  • ISAPI Filter Connectors allows preprocessing of packets before they enter or leave the IIS process. This includes SSL (Secure Sockets Layer) implementation.

ISAPI programs run as DLLs and are loaded when the HTTP is started. Unlike CGI programs, ISAPI programs do not have processes and address space separate from the HTTP program. This allows ISAPI programs to be instantly accessible.

There are other application configuration setting available including setting CGI Script Timeout limits, the caching of ISAPI apps, ASP configurations, and ASP debugging options.

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