The W3C has posted a working draft of State Chart XML (SCXML): State Machine Notation for Control Abstraction:
a general-purpose event-based state machine language that can be used in many ways, including:
- As a high-level dialog language controlling VoiceXML 3.0's encapsulated speech modules (voice form, voice picklist, etc.)
- As a voice application metalanguage, where in addition to VoiceXML 3.0 functionality, it may also control database access and business logic modules.
- As a multimodal control language in the MultiModal Interaction framework [W3C MMI], combining VoiceXML 3.0 dialogs with dialogs in other modalities including keyboard and mouse, ink, vision, haptics, etc. It may also control combined modalities such as lipreading (combined speech recognition and vision) speech input with keyboard as fallback, and multiple keyboards for multi-user editing.
- As the state machine framework for a future version of CCXML.
- As an extended call center management language, combining CCXML call control functionality with computer-telephony integration for call centers that integrate telephone calls with computer screen pops, as well as other types of message exchange such as chats, instant messaging, etc.
- As a general process control language in other contexts not involving speech processing.
SCXML combines concepts from CCXML and Harel State Tables. CCXML [W3C CCXML 1.0] is an event-based state machine language designed to support call control features in Voice Applications (specifically including VoiceXML but not limited to it). The CCXML 1.0 specification defines both a state machine and event handing syntax and a standardized set of call control elements. Harel State Tables are a state machine notation that was developed by the mathematician David Harel [Harel and Politi] and is included in UML [UML 2.0]. They offer a clean and well-thought out semantics for sophisticated constructs such as a parallel states. They have been defined as a graphical specification language, however, and hence do not have an XML representation. The goal of this document is to combine Harel semantics with an XML syntax that is a logical extension of CCXML's state and event notation.
