Many modern software systems are implemented as client/server architectures, where a server handles multiple clients concurrently. Testing does not cover the outcomes of all possible thread and communication schedules reliably. Software model checking, on the other hand, covers all possible outcomes but is often limited to subsets of commonly used protocols and libraries. Earlier work in cache-based software model checking handles implementations using socket-based TCP/IP networking, with one thread per client connection using blocking input/output. Recently, servers using non-blocking, selector-based input/output have become prevalent. This paper describes our work extending the Java PathFinder extension net-iocache to such software, and the application of our tool to modern server software.

A new algorithm for generating counterexamples for the temporal description logic ALCCTL is presented. ALCCTL is a decidable combination of the description logic ALC and computation tree logic CTL. It extends CTL by first order quantified expressions over unary and binary predicates. Predicates and quantified expressions are required for representing properties in application domains such as structured web documents and they are frequently used in software and hardware specifications which are verified by model checking. In the case of a specification violation, existing algorithms generate counterexamples that tend to be complex yet imprecise if specifications range over sets of objects. The presented algorithm is the first algorithm for generating counterexamples for a temporal description logic that considers first order predicates and quantification. The algorithm is sound and semi-complete for ALCCTL. The generated counterexamples are both more precise and comprehensible than counterexamples generated by the previous algorithms.

Checking the content coherence of digital documents is the purpose of the Verdikt system which can be applied to different domains and document types including technical documentation, e-learning documents, and web pages. An expressive temporal description logic allows for the specification of content consistency criteria along document paths. Whether the document conforms to the specification can then be verified by applying a model checker. In case of specification violations, the model checker provides counterexamples, locating errors in the document precisely. Based on a sample technical documentation in the form of a web document, the general verification process and its effectiveness, efficiency, and usability are demonstrated.