Applying KAoS Services to Ensure Policy Compliance for Semantic Web Services Workflow Composition and Enactment Andrzej Uszok, Jeffrey M. Bradshaw, Renia Jeffers Institute for Human and Machine Cognition (IHMC), 40 S. Alcaniz, Pensacola, FL 32501, USA {auszok, jbradshaw, rjeffers}@ihmc.us Austin Tate, Jeff Dalton Artificial Intelligence Applications Institute, University of Edinburgh, Edinburgh EH8 9LE, UK {a.tate, j.dalton}@ed.ac.uk Abstract In this paper we describe our experience in applying KAoS services to ensure policy compliance for Semantic Web Services workflow composition and enactment. We are developing these capabilities within the context of two applications: Coalition Search and Rescue (CoSAR-TS) and Semantic Firewall (SFW). We describe how this work has uncovered requirements for increasing the expressivity of policy beyond what can be done with description logic (e.g., role-value-maps), and how we are extending our representation and reasoning mechanisms in a carefully controlled manner to that end. Since KAoS employs OWL for policy representation, it fits naturally with the use of OWL-S workflow descriptions generated by the AIAI I-X planning system in the CoSAR- TS application. The advanced reasoning mechanisms of KAoS are based on the JTP inference engine and enable the analysis of classes and instances of processes from a policy perspective. As the result of analysis, KAoS concludes whether a particular workflow step is allowed by policy and whether the performance of this step would incur additional policy-generated obligations. Issues in the representation of processes within OWL-S are described. Besides what is done during workflow composition, aspects of policy compliance can be checked at runtime when a workflow is enacted. We illustrate these capabilities through two application examples. Finally, we outline plans for future work. 1. Introduction Despite rapid advances in Web Services, the demanding requirements of the user community continue to outstrip currently available technology solutions. To help close this gap, advocates of Semantic Web Services have begun to define and implement many new and significant capabilities (http://www.swsi.org/). These new capabilities are intended to more fully harness the power of Web Services through explicit representations of the semantics underlying Web resources and the development of intelligent Web infrastructure capable of fully exploiting them. Semantic Web Languages such as OWL extend RDF to allow users to specify ontologies composed of taxonomies of classes and inference rules.

2 Semantic Web Services can be effectively used not only by people but also by software agents [10]. Agents will increasingly use the combination of semantic markup languages and Semantic Web Services to understand and autonomously manipulate Web content in significant ways. Agents will discover, communicate, and cooperate with other agents and services and, as described in this paper, will rely on policy-based management and control mechanisms to ensure that human-imposed constraints on agent interaction are respected. Policy-based controls of Semantic Web Services can also be used to govern interaction with traditional (non-agent) clients. 2. Policies and Semantic Web Services Policies, which constrain the behavior of system components, are becoming an increasingly popular approach to dynamic adjustability of applications in academia and industry (http://www.policy-workshop.org/). Elsewhere we have pointed out the many benefits of policy-based approaches, including reusability, efficiency, extensibility, context-sensitivity, verifiability, support for both simple and sophisticated components, protection from poorly-designed, buggy, or malicious components, and reasoning about their behavior [2]. Policies have important analogues in animal societies and human cultures [6]. Policy-based network and distributed system management has been the subject of extensive research over the last decade (http://www- dse.doc.ic.ac.uk/Research/policies/) [18]. Policies are often applied to automate network administration tasks, such as configuration, security, recovery, or quality of service (QoS). In the network management field, policies are expressed as sets of rules governing choices in the behavior of the network. There are also ongoing standardization efforts toward common policy information models and frameworks. The Internet Engineering Task Force, for instance, has been investigating policies as a means for managing IP-multiservice networks by focusing on the specification of protocols and object-oriented models for representing policies (http://www.ietf.org/html.charters/policy-charter.html). The scope of policy management is increasingly going beyond these traditional applications in significant ways. New challenges for policy management include: ��� Sources and methods protection, digital rights management, information filtering and transformation, and capability-based access ��� Active networks, agile computing, pervasive and mobile systems ��� Organizational modeling, coalition formation, formalizing cross-organizational agreements ��� Trust models, trust management, information pedigrees ��� Effective human-machine interaction: interruption and notification management, presence management, adjustable autonomy, teamwork facilitation, safety and ��� Support for humans trying to retrieve, understand, and analyze all policies relevant to some situation. Multiple approaches for policy specification have been proposed that range from formal policy languages that can be processed and interpreted easily and directly by a computer, to rule-based policy notation using an if-then-else format, to the representation of policies as entries in a table consisting of multiple attributes.

3 In the Web Services world, standards for SOAP-based message security1 and XML- based languages for access control (e.g., XACML2) have begun to appear. However the immaturity of the current tools along with the limited scope and semantics of the new languages make them less-than-ideal candidates for the sorts of sophisticated Web-based applications its visionaries have imagined for the next decade [7 12]. The use of XML as a standard for policy expression has both advantages and disadvantages. The major advantage of using XML is its straightforward extensibility (a feature shared with languages such as RDF and OWL, which are built using XML as a foundation). The problem with mere XML is that its semantics are mostly implicit. Meaning is conveyed based on a shared understanding derived from human consensus. The disadvantage of implicit semantics is that they are rife with ambiguity, promote fragmentation into incompatible representation variations, and require extra manual work that could be eliminated by a richer representation. However Semantic Web-based policy representations, such as those described in this paper, could be mapped to lower level representations if required by an implementation by applying contextual information. In addition to our own work on KAoS (see below), some initial efforts in the use of Semantic Web representations for basic security applications (authentication, access control, data integrity, and encryption) of policy have begun to bear fruit. For example, Denker et al. have integrated a set of ontologies (credentials, security mechanisms) and security extensions for OWL-S Service profiles with the CMU Semantic Matchmaker [12] to enable security brokering between agents and services. Future work will allow security services to be composed with other services. Kagal et al. [8] are developing Rei, a Semantic Web language-based policy language that is being used as part of the described above OWL-S Service profiles extension and other applications. In another promising direction, Li, Grosof, and Feigenbaum [9] have developed a logic-based approach to distributed authorization in large-scale, open, distributed systems. 3. KAoS Policy and Domain Management Services KAoS is one of the first efforts to represent policy using a Semantic Web language��� in this case OWL3. KAoS services and tools allow for the specification, management, conflict resolution, and enforcement of policies within the specific contexts established by complex organizational structures represented as domains [2 3 16 17]. While initially oriented to the dynamic and complex requirements of software agent applications, KAoS services have been extended to work equally well with both agent and traditional clients on a variety of general distributed computing platforms (e.g., CORBA, Web Services, Grid Computing (Globus GT3)). 3.1 Ontological Representation of KAoS Policies KAoS uses ontology concepts (encoded in OWL) to build policies. During its bootstrap, KAoS first loads a KAoS Policy Ontology (KPO) defining concepts used to 1 e.g., http://www-106.ibm.com/developerworks/webservices/library/ws-secure/ 2 http://www.oasis-open.org/committees/tc_home.php?wg_abbrev=security 3 A comparison among two semantically-rich representations of policy (KAoS, Rei) and amore traditional policy language (Ponder[5]) can be found in [15].