Conceptual Architecture

The conceptual architecture described in this chapter illustrates the basic capabilities of a Network Computer and how they relate to one another.

Note that this is an abstract architecture, and is in no way meant to describe the inner workings of any particular Network Computer, nor is it meant to dictate implementation. Instead, it is meant to help the reader understand how the various elements of a Network Computer might work together.

In Network Computer Abstract Architecture , the required elements of the architecture are denoted by solid lines, and the optional elements by dotted lines.

Provide a User Interface

Conforming products are required to provide a set of capabilities that together make up the interface between the system's user and the system services.

Process URLs

When a user enters or selects a Uniform Resource Locator (URL), this needs to be evaluated by the system. Depending upon the URL's scheme, different tasks will be performed:

• Establish and Conduct Virtual Terminal Sessions (optional)

  If the Terminal Emulation (see Terminal Emulation ) option is supported by the product, URLs using the telnet: scheme will cause a virtual terminal session between the user's system and the specified host to be established using the Telnet Protocol.

• Select and Retrieve Files (optional)

  If the File Transfer (see File Transfer ) option is supported by the product, URLs using the ftp: scheme will cause files, or lists of file names, to be obtained using the File Transfer Protocol.

• Send Mail

  URLs using the mailto: scheme will allow the composition and transmission of mail using the Simple Mail Transfer Protocol (SMTP).

• Transmit Resource Requests

  URLs using the http: or https: schemes will be sent to the specified host using the HTTP or Secure Socket Layer (SSL) protocol, respectively.

• Receive Requested Resources

  The resources referenced by URLs using the http: or https: schemes are received by the system and their contents made available for processing.

Execute Java Applets

When a Java bytecode file is referenced through the HTML <APPLET> tag, that bytecode file will be retrieved via the HyperText Transfer Protocol and executed.

Process and Present Resources

Resources that are requested via the URL http: or https: schemes have content types. These content types will cause them to be processed in different ways prior to rendering them to the product's output devices.