Abstract: A solution to the music-on-hold problem associated with audio conference calls. The music on-hold-problem occurs when a conferee having music-on-hold puts the conference call on hold, resulting in a continuous stream of music being transmitted to the other conferees. Such a conferee is called an offending conferee. The solution presented herein is to prevent music-on-hold signals emanating from an offending conferee from being passed through an audio conference bridge to the other conferees. This is accomplished, in particular embodiments, by directing a merging/summing subsystem of the audio conference bridge to temporarily stop combining audio emanating from the offending conferee from being combined or merged onto audio channels through which the other conferees communicate on the audio conference.

Abstract: Verification systems which employ automata-theoretic formal verification use a model automaton made from a system process (203) representing the system and a task automaton (205) representing the task and use the model automaton to test (217) whether the language of the system process is contained in the language of the task automaton. An improved technique reduces the computational complexity of the language containment testing by producing a model (216) which represents a system which has been automatically localized with regard to a task. Another technique reduces the computational complexity of stepwise refinement (208). In stepwise refinement, the system automaton is refined a step at a time until it reaches the complexity of a practical implementation. The computational complexity of the stepwise refinement is reduced by a technique which permits language containment to be tested using a set of models made from process-automaton pairs rather than process-process pairs.

Abstract: A method wherein a verification tool checks the properties of a system model by performing a partial search of the system-model state space. A partial search is a search wherein the verification tool inputs, at each state of the system-model state space, only a subset or fraction of the complete set of inputs that would have been used during a conventional search. Performing a partial search, instead of a conventional search, reduces the total number of inputs that the verification tool will input to the system model during a search of the system-model state space, thus reducing the amount of computational resources and/or time needed by the verification tool to verify given properties of the system model. Moreover, performing a partial search, instead of a conventional search, does not substantially reduce the ability of the verification tool to identify errors in the system-model.

Abstract: A method and apparatus for defining a system design specification by using a finite set of templates that have a format for accepting a set of system expression such that a selected template, when filled with the system expressions, defines an intended behavioral attribute of the system. In one illustrative embodiment, each template has a set of qualifiers and a set of entry blanks, wherein each qualifier is associated with an entry blank. In such an embodiment, the set of entry spaces may comprise a fulfilling condition entry space for accepting a system expression that defines a required or assumed event of the system model, an enabling condition entry space for accepting a system expression that defines a precondition for starting a check of the required or assumed event, and a discharging condition entry space for accepting a system expression that defines a condition after which said fulfilling condition is no longer required or assumed by the system model.

Abstract: The invention presents a method and apparatus for forming a restricted model from a system model to reduce the computational resources required to formally verify the system design, without substantially reducing the ability to test all system model functions, or properties. In general, the restricted model is formed by restricting the range of assumable values of system model variables and system model inputs to a restricted set of values, based on the values assumed by the system model variables and system model inputs during a partial search of the system model. The restricted model can then be fully searched by a conventional verification tool to identify system design errors. Advantageously, the restricted model requires less computational resources to verify the system design (i.e. through a full search) than the original system model.

Abstract: A method and apparatus for verifying the behavior of properties or functions of a system by forming a reduced model for each property of the system, and running a given simulation operation on the reduced model to verify the behavior of each said property. When a property or function does not behave as expected, the system model is adjusted, and only those functions having a property affected by the adjustment are rechecked. In one illustrative embodiment, a system model is reduced by eliminating all variables having no effect on the function or property being checked. The resulting reduced model can be further reduced by adjusting the range of each variable therein to a minimum range necessary to check the behavior of that specific property. If it becomes necessary to change the system model in order to fix a problem relative to one property, then only those properties having a reduced model affected by that change or fix are re-verified.