Steffen Lamparter

Preference-based selection of highly configurable web services

A key challenge for dynamic Web service selection is that Web services are typically highly configurable and service requesters often have dynamic preferences on service configurations. Current approaches, such as WS-Agreement, describe Web services by enumerating the various possible service configurations, an inefficient approach when dealing with numerous service attributes with large value spaces. We model Web service configurations and associated prices and preferences more compactly using utility function policies, which also allows us to draw from multi-attribute decision theory methods to develop an algorithm for optimal service selection. In this paper, we present an OWL ontology for the specification of configurable Web service offers and requests, and a flexible and extensible framework for optimal service selection that combines declarative logic-based matching rules with optimization methods, such as linear programming. Assuming additive price/preference functions, experimental results indicate that our algorithm introduces an overhead of only around 2 sec.~compared to random service selection, while giving optimal results. The overhead, as percentage of total time, decreases as the number of offers and configurations increase.

How Semantic Technologies Can Enhance Data Access at Siemens Energy

We present a description and analysis of the data access challenge in the Siemens Energy. We advocate for Ontology Based Data Access (OBDA) as a suitable Semantic Web driven technology to address the challenge. We derive requirements for applying OBDA in Siemens, review existing OBDA systems and discuss their limitations with respect to the Siemens requirements. We then introduce the Optique platform as a suitable OBDA solution for Siemens. Finally, we describe our preliminary installation and evaluation of the platform in Siemens.

SMART - a semantic matchmaking portal for electronic markets

Searching and comparing products in electronic markets is still a challenging problem. On one hand, the expressive power of the search mechanisms offered by the existing electronic markets is too limited. On the other hand, the price is mostly the only criterium of comparing the results with each other. In this paper, we introduce SMART (semantic matchmaking portal) to improve searching and comparing products in electronic markets. Therefore, we present a novel matchmaking approach based on fuzzy descriptions that provide a more expressive search mechanism that is closer to human reasoning and aggregates multiple search criteria to a single value (ranking of an offer relative to the query), thus enabling better selection of offers that should be considered for the negotiation.

Making Web services tradable

In service-oriented architectures, applications are developed by incorporating services which are often provided by different organizations. Since a service might be offered under different configurations by various different organizations, sophisticated service selection and negotiation algorithms are required. Policies capture the conditions under which services are offered or requested and thereby constrain the negotiation space. However, current policy languages are ill-suited to realize beneficial trade-offs within a negotiation, since they support only Boolean decisions and cannot capture all relevant service information. Therefore, we present a novel policy language in this work that provides two main contributions: (i) we enable the specification of constraints on functional as well as non-functional properties of Web services. The functional properties include data objects and the behaviour, whereas the non-functional properties include QoS attributes. (ii) Given such constraints, we show how the concept of utility function policies can be used to define cardinal preferences over functional as well as non-functional properties. This is required to rank Web service offers, define their prices, and consequently to realize automated negotiations between service providers and requesters.

Ontology-Based Integration of Streaming and Static Relational Data with Optique

Real-time processing of data coming from multiple heterogeneous data streams and static databases is a typical task in many industrial scenarios such as diagnostics of large machines. A complex diagnostic task may require a collection of up to hundreds of queries over such data. Although many of these queries retrieve data of the same kind, such as temperature measurements, they access structurally different data sources. In this work we show how Semantic Technologies implemented in our system optique can simplify such complex diagnostics by providing an abstraction layer---ontology---that integrates heterogeneous data. In a nutshell, optique allows complex diagnostic tasks to be expressed with just a few high-level semantic queries. The system can then automatically enrich these queries, translate them into a collection with a large number of low-level data queries, and finally optimise and efficiently execute the collection in a heavily distributed environment. We will demo the benefits of optique on a real world scenario from Siemens.

A policy framework for trading configurable goods and services in open electronic markets

In recent years, electronic markets have gained much attention as institutions to allocate goods and services efficiently between buyers and sellers. However, calculating suitable allocations between buyers and sellers in such markets can easily become very tricky, particularly if the services and goods involved are complex and described by multiple attributes. Since such trading objects typically provide various configurations with different corresponding prices, complex pricing functions and purchase preferences have to be taken into account when computing allocations. In this paper, we present a policy description framework that draws from utility theory to capture configurable products with multiple attributes. The framework thus allows the declarative description of seller pricing policies as well as buyer preferences over these configurations. As part of the framework, we present a machine-processible representation language for the policies and a method to evaluate different trading object configurations based on these policies. In addition, we show how policies can be aggregated and how the framework can be applied in a Web service selection scenario.

The impact of charging strategies for electric vehicles on power distribution networks

This work investigates four different generic charging strategies for battery electric vehicles (BEVs) with respect to their economic performance and their impact on the local power distribution network of a residential area in southern Germany. The charging strategies are Simple Charging (uncontrolled), Smart Charging (cost minimal), Vehicle to Grid Charging (V2G) and Heuristic V2G Charging. The simulation setting includes a high share of local renewable generation as well as typical residential load patterns to which different penetration levels of BEVs are added for the evaluation. Prices are determined on a regional energy market with agents representing the participating households (including PV generation and BEVs) as well as the traditional supply for the local power distribution network via the point of common coupling (PCC). Results show that Smart and V2G Charging lead to cost reductions for electric mobility of 40 % or 75% respectively per week and household. At the same time additional stress is put on the distribution network which shows a need for further coordination of BEV charging.

Trading services in ontology-driven markets

In order to realize the vision of a full-fletched service oriented architecture efficient service discovery and allocation is required to coordinate the interplay between service providers and requesters. This paper presents the architecture of an ontology-driven market for trading Semantic Web Services. An auction schema is enriched by a set of components enabling semantics based matching as well as price-based allocations. Moreover, an approach for reducing the complexity of the auction system by means of background knowledge is proposed.

Planning and Pricing of Service Mashups

Todays development and provision of commercially used Web services has shifted from providing static and predefined functionality to highly configurable services that can be dynamically combined by customers. This new form of composed services called service mashups integrate functionality of multiple sub-services from decentralized providers. Consequently this leads to a high configuration complexity and presents new challenges in the field of planning and pricing of service offerings such as validation of service configurations as well as price determination. Facing these challenges this paper presents an ontology framework for describing technical as well as economic interdependencies between services and shows how planning and pricing algorithms for dynamic Web scenarios can be implemented. As proof of concept we present the implementation of a service mashup planner and show how this tool can be used to construct complex services considering technical as well as economic service aspects.

Formal Specification of Web Service Contracts for Automated Contracting and Monitoring

Service-oriented computing as a concept for providing interoperability and flexibility within heterogeneous environments has gained much attention within the last few years. Dynamically integrating external Web services into enterprise applications requires automatic contracting between service requestors and providers and automatic contract monitoring. This paper suggests a semi-automatic approach since in the current legal environment full automation is not feasible. We elaborate on the content of Web service contracts from a legal perspective and derive a set of legal requirements. Based on these requirements we propose an ontology-based representation of contract clauses as well as monitoring information. We can thus automatically evaluate whether a service execution meets the requirements expressed in a contract