This paper describes the Speech Application Language Tags, or SALT, an XML based spoken dialog standard for multimodal or speech-only applications. A key premise in SALT design is that speech-enabled user interface shares a lot of the design principles and computational requirements with the graphical user interface (GUI). As a result, it is logical to introduce into speech the object-oriented, event-driven model that is known to be flexible and powerful enough in meeting the requirements for realizing sophisticated GUIs. By reusing this rich infrastructure, dialog designers are relieved from having to develop the underlying computing infrastructure and can focus more on the core user interface design issues than on the computer and software engineering details. The paper focuses the discussion on the Web-based distributed computing environment and elaborates how SALT can be used to implement multimodal dialog systems.

SALT is an industrial standard that enables speech input/output for Web applications. Although the core design is to make simple tasks easy, SALT gives the designers ample fine-grained controls to create advanced user interface. The paper exploits a speech input mode in which SALT would dynamically report partial semantic parses while audio capturing is still ongoing. The semantic parses can be evaluated and the outcome reported immediately back to the user. The potential impact for the dialog systems is that tasks conventionally performed in a system turn can now be carried out in the midst of a user turn, thereby presenting a significant departure from the conventional turn-taking. To assess the efficacy of such highly interactive interface, more user studies are undoubtedly needed. This paper demonstrates how SALT can be employed to facilitate such studies.