Basic Specification

This chapter specifies the mandatory features for a conformant NC product. Optional Facilities defines optional facilities which may be included.

Unlike most existing specifications from The Open Group, this specification does not rely solely upon other specifications from The Open Group along with standards issued from formal standards bodies. Instead, it also references specifications that are widely recognized in the industry as being de facto standards. The majority of these specifications are developed by the Internet Engineering Task Force (IETF).

Providing a User Interface

• A display screen with a resolution of at least 640 x 480, or equivalent (including NTSC, PAL, and SECAM television display resolutions).

• Pointing capability.

• Text input capability.

• Audio output.

Processing Uniform Resource Locators

• URLs are of the form scheme : scheme-specific-data.

• In most cases the scheme-specific-data includes a hostname. This is a string that represents the unique name of a system on the network to which the product is attached.

  The hostname portion of a URL shall be translated into that host's Internet Protocol address by querying a name server using the protocol defined in Internet Standard 13, Domain Name System:

  • IETF RFC 1034, Domain Names - Concepts and Facilities

  • IETF RFC 1035, Domain Names - Implementation and Specification.

  These queries are sent using the User Datagram Protocol (see User Datagram Protocol ) over an Internet Protocol-based network (see Internet Protocol ).

• The scheme-specific-data may also include a url-path. This is a unique identifier for the resource being requested on the system represented by the hostname.

URLs may be entered in an implementation-defined manner using the text input capability, or may be selected using a hypertext link in a displayed HTML resource that contains the tag <A HREF=>...</A>. When the user enters or selects a URL, they are said to be "using" that URL. When a URL is used, the NC shall provide the appropriate service.

The remainder of this section describes the various schemes available, and how a conformant NC will process each scheme. Where the processing of a scheme is optional, this is clearly indicated.

Transmit Resource Requests

Resources returned in response to a transmitted request shall be made available for processing directly to Java Applets (see Processing and Presentation of Resources ), or to the user if the user made the request. The implementation shall be able to process responses that are encoded using either HTTP/1.0 or HTTP/1.1 protocols.

Send Mail

• IETF RFC 822, Standard for the Format of ARPA Internet Text Messages.

When such a URL is used, the NC shall do the following:

• Open a window for message composition.

• Set as the default destination address for the message the <rfc822-addr-spec> portion of the URL, if any.

• Allow the user to specify/change the destination address for the message.

• Allow the user to specify an address to which the recipient of the message could reply.

• Allow the user to specify a subject for the message.

• Allow the user to compose a message.

• Allow the user to indicate when the message is ready to be sent.

• Provide a means for the user to abort the process without sending the message.

The message shall be transmitted to the recipient(s) using the protocol defined in Internet Standard 10, Simple Mail Transfer Protocol:

• IETF RFC 821, Simple Mail Transfer Protocol,

• IETF RFC 1870, SMTP Service Extension for Message Size Declaration,

• IETF RFC 1869, SMTP Service Extensions.

The structure of the transmitted message shall conform to the standards defined in Internet Standard 11, Format of Electronic Mail Messages:

• IETF RFC 822, Standard for the Format of ARPA Internet Text Messages

• IETF RFC 1049, Content Type Header Field.

The transmitted messages may also use the extensions defined in IETF RFC 1521, MIME (Multipurpose Internet Mail Extensions) - Part 1: Mechanisms for Specifying and Describing the Format of Internet Message Bodies.

It is implementation-defined whether the messages are transmitted through an SMTP relay host, or whether messages are sent from the product directly to each recipient.

The NC shall determine the Internet Protocol address of the hostname of each message recipient using the Domain Name Service as described in Processing Uniform Resource Locators . However, the Internet Protocol address shall be determined by using the method specified in Internet Standard 14, Mail Routing and the Domain System:

• IETF RFC 974, Mail Routing and the Domain System.

Note that a conformant NC is only required to act as an SMTP client, sending messages to SMTP servers. It need not be able to receive incoming messages.

Select and Retrieve Files

ftp : // username : password @ hostname : port / url-path.

When a URL of this scheme is used, and the product supports the File Transfer option (see File Transfer ), the NC shall attempt to open a connection with the host named by the hostname portion of the URL.

Establish and Conduct Virtual Terminal Sessions

telnet : // username : password @ hostname : port.

If a URL of this scheme is used, and the product supports the Terminal Emulation option (see Terminal Emulation ), a virtual terminal connection to the host named in the hostname portion of the URL shall be opened. If a username and password are specified, then the NC shall attempt to negotiate a login.

Processing and Presentation of Resources

When such resources are sent, the header portion of the resources can contain several pieces of information.

One such piece is a declaration of the resource's character set encoding. This optional header may specify the character set of the following data. The ISO 8859-1:1987ISO 8859-1:1987.

Another header element is the Content-type: . The NC evaluates this header to determine the resource's type, process the resource, and present it appropriately. The NC must process and present at least the following content types:

• Text/plain

  Text/plain shall be rendered on the display as plain text.

• Text/html

  Text/html shall be processed and the results rendered on the display in accordance with the rules of the HyperText Mark-up Language (HTML) defined in HTML 3.2, HTML 3.2 Reference Specification.

  When processing resources of this type, the NC shall:

  • Load and execute Applets (see Executing Java Applets ) when an <APPLET> tag is present.

  • Load, decode, and render GIF and JPEG format images when an <IMG> tag is present and refer to a resource with one of these types.

• Image/gif

  Image/gif shall be decoded in accordance with the Graphics Interchange Format Specification (GIF), Version 89a, and the results rendered on the display.

• Image/jpeg

  Image/jpeg shall be decoded in accordance with ISO/IEC 10918-1:1994.JPEG File Information Format (JFIF) Specificationhref="#tagbadchar">[??] as defined in ISO/IEC 10918-1:1994. The results of decoding such a resource shall be rendered on the display.

• Audio/basic

  Audio/basic shall be processed and sent to the audio device in accordance with the Audio File Information Format (.au), Sun Microsystems, and the results emitted through the product's audio output device.

• Audio/x-wav

  Audio/x-wav shall be processed and sent to the audio output device in accordance with the MMIO_5, Waveform Structures (files), encapsulated as RIFF Waveform Audio Format, Microsoft.

• Multipart/mixed

  Multipart/mixed shall be processed in accordance with the definition in IETF RFC 1521, MIME (Multipurpose Internet Mail Extensions) - Part 1: Mechanisms for Specifying and Describing the Format of Internet Message Bodies, as refined by the definitions in IETF RFC 1945, Hypertext Transfer Protocol - HTTP/1.0. Each boundary-separated body bgcolor="#FFFFFF"-part that is of a content type supported by the NC (including at least the set described here) shall be processed in turn.

Executing Java Applets

The NC shall provide a set of services that permit the execution of pre-compiled applications that use the Java Virtual Machine. This environment consists of two parts: the Java Virtual Machine and the Java Class Libraries.

The Java Class Libraries shall support referencing URLs with content types of audio/basic, audio/x-wav, image/gif, and image/jpeg (as defined above).

The product requirements necessary for support of the execution of Java Applets are given in the following documents:

• JAVA, Java Virtual Machine Specification

• JAVA_API Java Platform 1.1 Core API

Applications developed in the Java Programming Language, using only those classes defined in Javasoft's JDK 1.1 class libraries named "java.", and compiled using a Java byte code compiler equivalent to the one in Javasoft's JDK 1., shall execute without change on a conforming product.

Footnotes

1.

ISO 8859-1:1987, Information Processing - 8-bit Single-byte Coded Graphic Character Sets - Part 1: Latin Alphabet No. 1.

2.

ISO/IEC 10918-1:1994, Information Technology - Digital Compression and Coding of Continuous-tone Still Images - Part 1: Requirements and Guidelines.

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