Names and Subject-Based Addressing

Subject-based addressing technology helps messages reach their destinations without involving programmers in the details of network addresses, protocols, hardware and operating system differences, ports and sockets. Subject-based addressing conventions define a simple, uniform name space for messages and their destinations.

Programs that produce data arrange that data into messages, label each outbound message with a subject name, and send those messages. Programs that consume data receive it by listening to subject names; a consumer listening to a subject name receives all messages labeled with that name, from the time it begins listening until it stops listening.

A subject name is a character string that specifies the destination of a message, and can also describe the message content. For programs to communicate, they must agree upon a subject name at which to rendezvous (hence the name of this product). Subject-based addressing technology enables anonymous rendezvous, an important breakthrough, which decouples programs from the network addresses of specific computers.

Communication between programs is also anonymous—consumers need not know where or how data is produced, and producers need not know where data is consumed, nor how it is used. Producers and consumers only need to agree to label data items with the same set of subject names, and that the actual data be in a form that both can manipulate and interpret.

Anonymous communication decouples data consumers from data producers. Consumers are insulated from most changes in data producing software, including the replacement of producer processes, and the shifting of responsibilities among a collection of producer processes.

Subject-based addressing technology places few restrictions on the syntax and interpretation of subject names. System designers and developers have the freedom (and responsibility) to establish conventions for using subject names. For more information, see Subject Name Syntax.

Programs can listen for wildcard subject names to access a collection of related data through a single subscription. For more information about wildcard subjects, see Using Wildcards to Receive Related Subjects.

Subject Names

Subject names consist of one or more elements separated by dot characters (periods). The elements can be used to implement a subject name hierarchy that reflects the structure of information in an application system.

These strings are examples of valid subject names:

RUN.HOME

RUN.for.Elected_office.President