Abstract
Process management systems play an important role for today's information systems. They coordinate the work items among employees and ensure the correct execution of processes. In this paper we focus on the organizational perspective of process management systems. This perspective is responsible for assigning people together with their roles within business organizations to process execution. A key issue in integrating the organizational perspective into processes is the strategy for selecting people to execute work steps. This assignment is the basis for collaboration among the people of an organization within a process-based application. We implemented our approach in ESProNa, a Logtalk application running in SWI-Prolog extended with the Thea library providing direct and complete support for OWL2 ontologies. The use of these languages allows the definition of comprehensive organizational constraints. We will cover both, the definition of these constraints in the process model, and their interpretation by the process execution engine. Further we will show how the organizational perspective impacts the order of process execution, i. e. the way of collaboration between the assigned people decisively. © 2010 ICST.

Abstract
We describe and compare design choices for meta-predicate semantics, as found in representative Prolog module systems and in Logtalk. We look at the consequences of these design choices from a pragmatic perspective, discussing explicit qualification semantics, com- putational reflection support, expressiveness of meta-predicate declara- tions, safety of meta-predicate definitions, portability of meta-predicate definitions, and meta-predicate performance. Our aim is to provide use- ful insight for debating meta-predicate semantics and portability issues based on actual implementations and common usage patterns.

Abstract
In this paper we describe how declarative process modeling together with ontologies can be used to build complex clinical process models. Our approach supports the definition of functional, behavioral, organizational, data and operational process perspectives, resulting in an expressive and flexible modeling language. We use constraints for representing inter-process dependencies and constraint propagation for finding which processes are executable in user selected or given scenarios. Knowledge about the organizational perspective of a clinical ontology can be represented and imported from RDF files for interfacing with other applications. We implemented our approach in ESProNa, a Logtalk application running on SWI-Prolog extended with the CLP(FD) constraint library and the N3 parser Henry.

Abstract
One of the main advantages of Logic Programming (LP) is that it provides an excellent framework for the parallel execution of programs. In this work we investigate novel techniques to efficiently exploit parallelism from real-world applications in low cost multi-core architectures. To achieve these goals, we revive and redesign the YapOr system to exploit or-parallelism based on a multi-threaded implementation. Our new approach takes full advantage of the state-of-the-art fast and optimized YAP Prolog engine and shares the underlying execution environment, scheduler and most of the data structures used to support YapOr's model. Initial experiments with our new approach consistently achieve almost linear speedups for most of the applications, proving itself as a good alternative for exploiting implicit parallelism in the currently available low cost multi-core architectures.

Abstract
Inference in many probabilistic logic systems is based on representing the proofs of a query as a DNF Boolean formula. Assessing the probability of such a formula is known as a #P-hard task. In practice, a large DNF is given to a BDD software package to construct the corresponding BDD. The DNF has to be transformed into the input format of the package. This is the preprocessing step. In this paper we investigate and compare different preprocessing methods, including our new trie based approach. Our experiments within the ProbLog system show that the behaviour of the methods changes according to the amount of sharing in the original DNF. The decomposition method is preferred when there is not much sharing in the DNF, whereas DNFs with sharing benefit from our trie based method. While our methods are motivated and applied in the ProbLog context, our results are interesting for other applications that manipulate DNF Boolean formulae.

Abstract
Tabled evaluation is a recognized and powerful implementation technique that overcomes some limitations of traditional Prolog systems in dealing with recursion and redundant sub-computations. Tabling based systems use call similarity to determine if a tabled subgoal will produce their own answers or if it will consume from another subgoal. While call variance has been a very popular approach, call subsumption can yield superior time performance and space improvements as it allows greater reuse of answers. However, the call order of the subgoals can greatly affect the success and applicability of the call subsumption technique. In this work, we present an extension, named Retroactive Call Subsumption, that supports call subsumption by allowing full sharing of answers between subsumed/subsuming subgoals, independently on the order in which they are called. Our experiments using the YapTab tabling engine show considerable gains in evaluation time for some applications, at the expense of a very small overhead for the programs that cannot benefit from it.