Peep Küngas

Logic-based Web services composition: from service description to process model

This paper introduces a method for automatic composition of semantic Web services using Linear Logic (LL) theorem proving. The method uses semantic Web service language (DAML-S) for external presentation of Web services, while, internally, the services are presented by extralogical axioms and proofs in LL. We use a process calculus to present the composite service formally. The process calculus is attached to the LL inference rules in the style of type theory. Thus the process model for a composite service can be generated directly from the proof. The subtyping rules that are used for semantic reasoning are presented with LL inference figures. We propose a system architecture where the DAML-S translator, the LL theorem prover and the semantic reasoner can operate together to fulfill the task. This architecture has been implemented in Java.

Composition of Semantic Web services using Linear Logic theorem proving

This paper introduces a method for automatic composition of Semantic Web services using Linear Logic (LL) theorem proving. The method uses a Semantic Web service language (DAML-S) for external presentation of Web services, while, internally, the services are presented by extralogical axioms and proofs in LL. LL, as a resource conscious logic, enables us to capture the concurrent features of Web services formally (including parameters, states and non-functional attributes). We use a process calculus to present the process model of the composite service. The process calculus is attached to the LL inference rules in the style of type theory. Thus, the process model for a composite service can be generated directly from the complete proof. We introduce a set of subtyping rules that defines a valid dataflow for composite services. The subtyping rules that are used for semantic reasoning are presented with LL inference figures. We propose a system architecture where the DAML-S Translator, LL Theorem Prover and Semantic Reasoner can operate together. This architecture has been implemented in Java.

Cost-Effective Semantic Annotation of XML Schemas and Web Service Interfaces

Research in the field of semantic Web services aims at automating the discovery, selection, composition and management of Web services based on semantic descriptions. However, the applicability of many solutions developed in this field is hampered by the costs associated with semantically annotating large repositories of Web services. To overcome this gap we propose a practical method for semantically annotating collections of XML Schemas and Web service interfaces. We have evaluated this method on a large repository of governmental Web services. The evaluation shows that relatively simple techniques are surprisingly cost-effective, saving hundreds of man-hours of semantic annotation effort. Moreover, the proposed method does not assume the availability of a preexisting ontology or controlled vocabulary. Instead, the space of annotations is dynamically built during the annotation process.

Semantic web service composition through a p2p-based multi-agent environment

This paper describes a multi agent system (MAS) for distributed composition of Semantic Web services. Since our system is intended to function in highly dynamic environments, where heterogeneous agents rapidly join and leave the system, we consider P2P approach as most suitable for facilitating agent and service discovery. The MAS is based on Chord P2P network, which allows the MAS to dynamically publish and locate available Semantic Web services, which are specified with OWL-S. In order to compose new Web services from existing ones, agents apply symbolic reasoning in a cooperative problem solving manner.

Symbolic Agent Negotiation for Semantic Web Service Exploitation

This paper presents an architecture and a methodology for agent-based Web service discovery and composition. We assume that Web services are described with declarative specifications like DAML-S. Based on the declarative information about services, symbolic reasoning can be applied while searching for or composing automatically new services. We propose that symbolic agent negotiation could be used for dynamic Web service discovery and composition. Symbolic negotiation, as we consider it here, is a mixture of distributed planning and information exchange. Therefore, by using symbolic negotiation for automated service composition, we support information collection and integration during service composition. The latter aspect has been largely neglected in automated service composition until now.

Ontology learning for cost-effective large-scale semantic annotation of web service interfaces

In this paper we introduce a novel unsupervised ontology learning approach, which can be used to automatically derive a reference ontology from a corpus of web services for annotating semantically the Web services in the absence of a core ontology. Our approach relies on shallow parsing technique from natural language processing in order to identify grammatical patterns of web service message element/part names and exploit them in construction of the ontology. The generated ontology is further enriched by introducing relationships between similar concepts. The experimental results on a set of global Web services indicate that the proposed ontology learning approach generates an ontology, which can be used to automatically annotate around 52% of element part and field names in a large corpus of heterogeneous Web services.

Petri net reachability checking is polynomial with optimal abstraction hierarchies

The Petri net model is a powerful state transition oriented model to analyse, model and evaluate asynchronous and concurrent systems. However, like other state transition models, it encounters the state explosion problem. The size of the state space increases exponentially with the system complexity. This paper is concerned with a method of abstracting automatically Petri nets to simpler representations, which are ordered with respect to their size. Thus it becomes possible to check Petri net reachability incrementally. With incremental approach we can overcome the exponential nature of Petri net reachability checking. We show that by using the incremental approach, the upper computational complexity bound for Petri net reachability checking with optimal abstraction hierarchies is polynomial. The method we propose considers structural properties of a Petri net as well an initial and a final marking. In addition to Petri net abstraction irrelevant transitions for a given reachability problem are determined. By removing these transitions from a net, impact of the state explosion problem is reduced even more.

Applying Semantic Web Service Composition for Action Planning in Multi-robot Systems

In this paper we demonstrate how the Web services based solutions can be effectively utilized and integrated into robotic world. In particular, we consider robotic systems where overall control is not embedded into any of the robots and the local behavior of each robot is loosely dependent on behavior of other robots. We propose an architecture for swarm action planning based on Web services paradigm exploiting a problem ontology for service discovery, linear logic based service composition for action planning and a task allocation layer for finding the most suitable robot to perform an action. In our solution all entities in the system expose their functionalities as Web services and allow dynamic service discovery and selection.

Symbolic negotiation with linear logic

Negotiation over resources and multi-agent planning are important issues in multi-agent systems research. Previously it has been demonstrated [18] how symbolic negotiation and distributed planning together could be formalised as distributed Linear Logic (LL) theorem proving. LL has been chosen mainly because of its expressive power for representation of resources and its computation-oriented nature. This paper extends the previous work by taking advantage of a richer fragment of LL and introducing two sorts of nondeterministic choices into negotiation. This allows agents to reason and negotiate under certain degree of uncertainty. Additionally, a way of granting unbounded access to resources during negotiation is considered. Finally we extend our framework with first-order LL for expressing more complex offers during negotiation.

Web Services Roadmap: The Semantic Web Perspective

Recently the field of Web services has gained focus both in industry and academia. While industry has been mostly interested in standardisation and promotion of the technology, academia has been looking for ways to fit the technology into other frameworks, such as the SemanticWeb. Anyway, despite of the increased academic and commercial interest to Web services, there are currently only few case studies available about Web services in the Semantic Web context. Moreover, according to authors’ knowledge, there is no publicly available study analysing which data is currently mostly provided/required by Web services. In this paper we target these shortcomings by providing a case study of semantically annotated commercial and governmental Web services. We analyse interaction and potential synergy between commercial and governmental Web services. Also the role ontologies for semantic integration of Web services is analysed. Moreover, we identify the most common data exploited by current Web services.