Handling Conflicts in Depth-First Search for LTL Tableau to Debug Compliance Based Languages

Providing adequate tools to tackle the problem of inconsistent compliance rules is a critical research topic. This problem is of paramount importance to achieve automatic support for early declarative design and to support evolution of rules in contract-based or service-based systems. In this paper we investigate the problem of extracting temporal unsatisfiable cores in order to detect the inconsistent part of a specification. We extend conflict-driven SAT-solver to provide a new conflict-driven depth-first-search solver for temporal logic. We use this solver to compute LTL unsatisfiable cores without re-exploring the history of the solver.Comment: In Proceedings FLACOS 2011, arXiv:1109.239

Verification of business process specifications with arithmetic and data dependencies

Recent years have witnessed the evolution of business process specification frameworks from the traditional process-centric approach towards data-awareness. Process- centric formalisms focus on control flow while under- specifying the underlying data and its manipulations by the process tasks, often abstracting them away completely. In contrast, data-aware formalisms treat data as first- class citizens. The presence of data implies an increase expressiveness of business process specification, including often data dependencies and arithmetic. This thesis studies the verification problem of temporal properties on data-aware business specifications with data dependencies and arithmetic. In our context, data implies infinite-state systems, for which verification is notoriously difficult. Unlike previous work, we focus on verification that is a) automatic (i.e. no expert user is required to help the process of verification as for theorem provers), b) sound and complete, and c) does not abstract away the data portion, retaining the ability to check the effects of data values on the behavior of the process (e.g. in a prototypical e-commerce business process, abstracting the data would make it impossible to check if the payment received for a product matches the price reported on the bill). We identify a practically significant class of business process specifications with data dependencies and arithmetic, for which verification of temporal properties is decidable. Besides decidability, in the context of commonly occurring classes of specifications, we develop verification techniques with upper bounds palatable to implementation, e.g. PSPACE for a common class of specifications with unary keys and fixed -arity databases with acyclic foreign keys. We implement a verifier prototype based on our theoretical results and measure the running times of the verification of temporal properties on a wide range of business process specifications of different complexities. Our random generation is based on patterns and frequencies found in real-world business process specifications and properties. The average running times measured range from seconds to minutes for the more complex specifications. We argue that the work in this thesis proves the feasibility of automatic verification of temporal properties on highly expressive business process specifications, that is both sound and complet

Verification of Business Process Specifications With Arithmetic and Data Dependencies

Recent years have witnessed the evolution of business process specification frameworks from the traditional process-centric approach towards data-awareness. Process-centric formalisms focus on control flow while under-specifying the underlying data and its manipulations by the process tasks, often abstracting them away completely. In contrast, data-aware formalisms treat data as first-class citizens. The presence of data implies an increase expressiveness of business process specification, including often data dependencies and arithmetic. This thesis studies the verification problem of temporal properties on data-aware business specifications with data dependencies and arithmetic. In our context, data implies infinite-state systems, for which verification is notoriously difficult. Unlike previous work, we focus on verification that is (a) automatic (i.e. no expert user is required to help the process of verification as for theorem provers), (b) sound and complete, and (c) does not abstract away the data portion, retaining the ability to check the effects of data values on the behavior of the process (e.g. in a prototypical e-commerce business process, abstracting the data would make it impossible to check if the payment received for a product matches the price reported on the bill). We identify a practically significant class of business process specifications with data dependencies and arithmetic, for which verification of temporal properties is decidable. Besides decidability, in the context of commonly occurring classes of specifications, we develop verification techniques with upper bounds palatable to implementation, e.g. PSPACE for a common class of specifications with unary keys and fixed-arity databases with acyclic foreign keys. We implement a verifier prototype based on our theoretical results and measure the running times of the verification of temporal properties on a wide range of business process specifications of different complexities. Our random generation is based on patterns and frequencies found in real-world business process specifications and properties. The average running times measured range from seconds to minutes for the more complex specifications. We argue that the work in this thesis proves the feasibility of automatic verification of temporal properties on highly expressive business process specifications, that is both sound and complete

Artifact systems with data dependencies and arithmetic

We revisit the static verification problem for data centric business processes, specified in a variant of IBM’s “business artifact” model. Artifacts are records of variables that correspond to business-relevant objects and are updated by a set of services equipped with pre-and-post conditions, that implement business process tasks. The verification problem consists in statically checking whether all runs of an artifact system satisfy desirable properties expressed in a firstorder extension of linear-time temporal logic. In previous work we identified the class of guarded artifact systems and properties, for which verification is decidable. However, the results suffer from an important limitation: they fail in the presence of even very simple data dependencies or arithmetic, both crucial to real-life business processes. In this paper, we extend the artifact model and verification results to alleviate this limitation. We identify a practically significant class of business artifacts with data dependencies and arithmetic, for which verification is decidable. The technical machinery needed to establish the results is fundamentally different from our previous work. While the worst-case complexity of verification is non-elementary, we identify various realistic restrictions yielding more palatable upper bounds

Artifact systems with data dependencies and arithmetic

We revisit the static verification problem for data centric business processes, specified in a variant of IBM’s “business artifact ” model. Artifacts are records of variables that correspond to business-relevant objects and are updated by a set of services equipped with pre-andpost conditions, that implement business process tasks. The verification problem consists in statically checking whether all runs of an artifact system satisfy desirable properties expressed in a firstorder extension of linear-time temporal logic. In previous work we identified the class of guarded artifact systems and properties, for which verification is decidable. However, the results suffer from an important limitation: they fail in the presence of even very simple data dependencies or arithmetic, both crucial to real-life business processes. In this paper, we extend the artifact model and verification results to alleviate this limitation. We identify a practically significant class of business artifacts with data dependencies and arithmetic, for which verification is decidable. The technical machinery needed to establish the results is fundamentally different from our previous work. While the worst-case complexity of verification is non-elementary, we identify various realistic restrictions yielding more palatable upper bounds