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<p>Multimedia application programs, including interactive television (ITV) applications, are often developed by using a "multimedia scripting language". The experience of many application designers is that it is often quite difficult to envision all the different situations that can be encountered in the course of a user session or game, and to ensure that the needed responses have indeed been included in the script. Before committing a widely replicated application over a publicly accessed network such as the phone or cable network, it is both desirable and cost-effective to ensure that an application is "customer-proof" to a certain extent -- so as to avoid unexpected, and potentially catastrophic, allocation of network resources. Unfortunately, most scripting platforms tend to ignore such "quality assurance" issues. </p> <p>We describe a methodology to address this problem. The content developers author applications using a graphical front end for a scripting language M that can be viewed as defining a hierarchy of "directors" and "actors". We have developed formal semantics for this scripting language in terms of an ensemble of interacting finite state machines that supports multimedia objects; a translator from M to another internal automaton-based representation that supports formal analysis has been implemented. Given this framework, properties pertaining to an interactive user session or game -- such as the possibility of deadlock, potential scenarios that might be encountered, resource utilization, etc.-- can be posed as queries that can be analytically answered using an associated tool set. Successful analysis of useful properties has been done on games that are part of a prototype ITV demonstration script. Our experiments underline the usefulness of performing formal analysis. </p> <p>Contact the authors at VLSI Systems Research Dept., Rm. 4E-530, Information Systems Laboratory, AT&T Bell Laboratories, 101 Crawfords Corner Rd., Holmdel, NJ 07733, e-mail; phone (908) 949-5812, fax (908) 949-9118. </p>
scripting, interactive television, formal methods, finite state machines

W. Schell, P. Subrahmanyam, K. Singh and G. Story, "Quality Assurance in Scripting," in IEEE MultiMedia, vol. 2, no. , pp. 50-59, 1995.
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