Michał Szychowiak

ReServE service: an approach to increase reliability in service oriented systems

Heterogeneous environment of service-oriented computing turns to be very error-prone, due to the loose-coupling and a great number of independent components that are susceptible to failures. Therefore, we propose the ReServE service, which improves the reliability of the SOA-based systems and applications. The proposed service ensures that after a failure occurrence, the state of a business process is transparently recovered, and it is consistently perceived by the business process participants: clients and web services.

Security Policy Definition Framework for SOA-Based Systems

This paper presents an extended architecture of a policy definition framework fine-tuned for service-oriented environments conforming to the SOA distributed processing paradigm. We establish key requirements for such a framework, and use these to confront existing distributed policy frameworks. We also define a policy language destined to fulfill all recognized requirements and give a brief overview of its syntax.

Applying message logging to support fault-tolerance of SOA systems

Abstract This paper addresses a problem of increasing fault-tolerance of serviceoriented systems built of RESTful web services. To solve such a problem, rollbackrecovery protocol is proposed. The protocol employs known rollback-recovery techniques, however, it modifies and specially adjusts them for specific characteristics of the SOA systems. The paper includes a proof of safety property of the proposed protocol.

Dependability Infrastructure for SOA Applications

This chapter describes two tools for improving dependability of SOA-based applications: ReSP (Reliable SOA Platform) and DyMST (Dynamic Management SOA Toolkit). ReSP is a set of modules to improve dependability in respect to availability and reliability, and to some extent safety. It is comprised of the mechanisms of reliable group communication, replication, recovery, and transaction processing. DyMST is a set of components for failure detection, monitoring and autonomic management, and distributed security policy enforcement. In order to show the dependability aspects of real applications and usage of these tools, two case studies from the medical healthcare domain are presented: Healthcare Integration Platform for the exchange of patients’ medical data among various healthcare units, and Medical Event, and Data Registering Platform for daily work improvement of medical staff.

An Extended Coherence Protocol for Recoverable DSM Systems with Causal Consistency

This paper presents a new checkpoint recovery protocol for Distributed Shared Memory (DSM) systems with read-write objects. It is based on independent checkpointing integrated with a coherence protocol for causal consistency model. That integration results in high availability of shared objects and ensures fast restoration of consistent state of the DSM in spite of multiple node failures, introducing little overhead. Moreover, in case of network partitioning, the extended protocol ensures that all the processes in majority partition of the DSM system can continuously access all the objects.

Checkpointing and rollback-recovery protocol for mobile systems with MW session guarantee

In the mobile environment, weak consistency replication of shared data is the key to obtaining high data availability, good access performance, and good scalability. Therefore new class of consistency models, called session guarantees, recommended for mobile environment, has been introduced. Session guarantees, called also client-centric consistency models, have been proposed to define required properties of the system regarding consistency from the clients point of view. Unfortunately, none of proposed consistency protocols providing session guarantees is resistant to server failures. Therefore, in this paper checkpointing and rollback-recovery protocol rVsMW, which preserves monotonic writes session guarantee is presented. The recovery protocol is integrated with the underlying consistency protocol by integrating operations of taking checkpoints with coherence operations of VsSG protocol.

Security Policy Conflicts in Service-oriented Systems

This paper considers methods for knowledge exploitation in security policies for Service-Oriented Architecture (SOA) environments, discovering the modality conflicts in particular. Two algorithms for discovering SOA-specific modality conflicts are proposed. First, a trivial (ad-hoc) approach is presented and further extended by the improved algorithm which offers lower time complexity. The formal verification of the proposal is followed by experimental results confirming the expected supremacy of the improved algorithm.

Lightweight information flow control for web services

This paper presents a concept of incorporating information flow control (IFC) mechanisms into service-oriented systems. As opposed to existing IFC proposals, commonly imposing requirements hard or impossible to achieve in service-oriented environments (such as analysis of the application code), our solution fully complies with the Service Oriented Architecture (SOA) model. We present how IFC can be managed in an SOA system by using ORCA security policy language. We also describe two possible implementations of such SOA-specific IFC mechanisms using cryptographic keys and poly-instantiated web services.

Modality conflict discovery for SOA security policies

This paper considers the problem of modality conflicts in security policies for Service-Oriented Architecture (SOA) environments. We describe the importance of this problem and present an algorithm for discovering modality conflicts with low overhead. Often being of large scale and compound structure, SOA systems can definitely benefit from that efficiency boost. Another advantage of the proposal over previously developed algorithms is its formal proof of correctness, also presented in this paper.

Low cost coherence protocol for DSM systems with processor consistency

Modern Distributed Shared Memory (DSM) systems offer high speed application processing by allowing to use relaxed consistency models, such as processor consistency. Unfortunately, most of the existing coherence protocols implementing relaxed consistency in multiprocessors or loosely couples clusters use write-update strategy which incurs large communication overhead, and therefore is impractical for most distributed applications. This paper presents a new home-based coherence protocol for DSM systems with processor consistency. The protocol uses local invalidation paradigm introducing little overhead. No additional invalidation messages are required; all coherence information is piggybacked to update messages.