The Messaging Open Service Interface Definition (OSID) is an O.K.I. specification which provides a means of sending, subscribing and receiving messages. OSIDs are programmatic interfaces which comprise a Service Oriented Architecture for designing and building reusable and interoperable software.

Each message has a Type and a Topic and what messages are received can be filtered by Type and Topic. Messages can be sent to a specific subset of subscribers (Agents) or to all subscribers. This OSID is a general service intended to interface with underlying email

Email

Electronic mail, commonly known as email or e-mail, is a method of exchanging digital messages from an author to one or more recipients. Modern email operates across the Internet or other computer networks. Some early email systems required that the author and the recipient both be online at the...

, chat

Online chat

Online chat may refer to any kind of communication over the Internet, that offers an instantaneous transmission of text-based messages from sender to receiver, hence the delay for visual access to the sent message shall not hamper the flow of communications in any of the directions...

, instant messaging

Instant messaging

Instant Messaging is a form of real-time direct text-based chatting communication in push mode between two or more people using personal computers or other devices, along with shared clients. The user's text is conveyed over a network, such as the Internet...

, or threaded discussion

Internet forum

An Internet forum, or message board, is an online discussion site where people can hold conversations in the form of posted messages. They differ from chat rooms in that messages are at least temporarily archived...

systems.