Skip to main content

2011 | Buch

Service-Oriented Computing

9th International Conference, ICSOC 2011, Paphos, Cyprus, December 5-8, 2011 Proceedings

herausgegeben von: Gerti Kappel, Zakaria Maamar, Hamid R. Motahari-Nezhad

Verlag: Springer Berlin Heidelberg

Buchreihe : Lecture Notes in Computer Science

insite
SUCHEN

Über dieses Buch

This book constitutes the refereed proceedings of the 9th International Conference on Service-Oriented Computing, ICSOC 2011, held in Paphos, Cyprus, in December 2011. The 54 revised papers presented were carefully reviewed and selected from 184 submissions. The papers are organized in topical sections on business process modeling, quality of service, formal methods, XaaS computing, service discovery, service security and trust, service runtime infrastructures and service applications.

Inhaltsverzeichnis

Frontmatter

Research Papers – Long

Business Process Modeling

Computing Degree of Parallelism for BPMN Processes

For sequential processes and workflows (i.e., pipelined tasks), each enactment (process instance) only has one task being performed at each time instant. When a process allows tasks to be performed in parallel, an enactment may have a number of tasks being performed concurrently and this number may change in time. We define the “degree of parallelism” of a process as the maximum number of tasks to be performed concurrently during an execution of the process. This paper initiates a study on computing degree of parallelism for three classes of BPMN processes, which are defined based on the use of BPMN gateways. For each class, an algorithm for computing degree of parallelism is presented. In particular, the algorithms for “homogeneous” and acyclic “choice-less” processes (respectively) have polynomial time complexity, while the algorithm for “asynchronous” processes runs in exponential time.

Yutian Sun, Jianwen Su
State Propagation in Abstracted Business Processes

Business process models are abstractions of concrete operational procedures that occur in the daily business of organizations. Typically one model is insufficient to describe one business process. For instance, a detailed technical model may enable automated process execution, while a more abstract model supports decision making and process monitoring by business users. Thereafter, multiple models capturing one process at various levels of abstraction often coexist. While the relations between such models are studied, little is known about the relations between process instances and abstract models.

In this paper we show how the state of an abstract activity can be calculated from the states of related, detailed process activities as they happen. The approach uses activity state propagation. With state uniqueness and state transition correctness we introduce formal properties that improve the understanding of state propagation. Algorithms to check these properties are devised. Finally, we use behavioral profiles to identify and classify behavioral inconsistencies in abstract process models that might occur, once activity state propagation is used.

Sergey Smirnov, Armin Zamani Farahani, Mathias Weske
Push-Enabling RESTful Business Processes

Representational State Transfer (REST)

as an architectural style for service design has seen substantial uptake in the past years. However, some areas such as

Business Process Modeling (BPM)

and push services so far have not been addressed in the context of REST principles. In this work, we look at how both BPM and push can be combined so that business processes can be modeled and observed in a RESTful way. Based on this approach, clients can subscribe to be notified when certain states in a business process are reached. Our goal is to design an architecture that brings REST’s claims of loose coupling and good scalability to the area of BPM, and still allow process-driven composition and interaction between resources to be modeled.

Cesare Pautasso, Erik Wilde

Quality of Service 1

QoS Analysis for Web Service Compositions Based on Probabilistic QoS

Quality of Service (QoS) analysis and prediction for Web service compositions is an important and challenging issue in distributed computing. In existing work, QoS for service compositions is either calculated based on constant QoS values or simulated based on probabilistic QoS distributions of component services. Simulation method is time consuming and can not be used in real-time applications for dynamic Web service compositions. In this paper, we propose a calculation method to estimate the QoS of a service composition, in which the probability distributions of the QoS of component services can be in any shape. Experimental results show that the proposed QoS calculation approach significantly improves the efficiency in probabilistic QoS estimation.

Huiyuan Zheng, Jian Yang, Weiliang Zhao, Athman Bouguettaya
Constraint-Based Runtime Prediction of SLA Violations in Service Orchestrations

Service compositions put together loosely-coupled component services to perform more complex, higher level, or cross-organizational tasks in a platform-independent manner. Quality-of-Service (QoS) properties, such as execution time, availability, or cost, are critical for their usability, and permissible boundaries for their values are defined in Service Level Agreements (SLAs). We propose a method whereby constraints that model SLA conformance and violation are derived at any given point of the execution of a service composition. These constraints are generated using the structure of the composition and properties of the component services, which can be either known or empirically measured. Violation of these constraints means that the corresponding scenario is unfeasible, while satisfaction gives values for the constrained variables (start / end times for activities, or number of loop iterations) which make the scenario possible. These results can be used to perform optimized service matching or trigger preventive adaptation or healing.

Dragan Ivanović, Manuel Carro, Manuel Hermenegildo
Optimizing Decisions in Web Services Orchestrations

Web services orchestrations conventionally employ exhaustive comparison of runtime quality of service (QoS) metrics for decision making. The ability to incorporate more complex mathematical packages are needed, especially in case of workflows for resource allocation and queuing systems. By modeling such optimization routines as service calls within orchestration specifications, techniques such as linear programming can be conveniently invoked by non-specialist workflow designers. Leveraging on previously developed QoS theory, we propose the use of a high-level flexible query procedure for embedding optimizations in languages such as Orc. The

Optima

site provides an extension to the sorting and pruning operations currently employed in Orc. Further, the lack of an objective technique for consolidating QoS metrics is a problem in identifying suitable cost functions. We employ the

analytical hierarchy process (AHP)

to generate a total ordering of QoS metrics across various domains. With constructs for ensuring

consistency

over subjective judgements, the AHP provides a suitable technique for producing objective cost functions. Using the

Dell Supply Chain

example, we demonstrate the feasibility of decision making through optimization routines, specially when the control flow is QoS dependent.

Ajay Kattepur, Albert Benveniste, Claude Jard

Formal Methods

Decidability Results for Choreography Realization

A service choreography defines a set of permitted sequences of message events as a specification for the interaction of services. Realizability is a fundamental sanity check for choreographies comparable to the notion of soundness for workflows.

We study several notions of realizability: partial, distributed, and complete realizability. They establish increasingly strict conditions on realizing services. We investigate decidability issues under the synchronous and asynchronous communication models. For partial realizability, we show undecidability whereas the other two problems are decidable with reasonable complexity.

Niels Lohmann, Karsten Wolf
Conformance Testing for Asynchronously Communicating Services

We suggest a black box testing approach to examine conformance for stateful services. Here, we consider asynchronous communication in which messages can overtake each other during their transmission. For testing, we generate partner services that exchange messages with the implementation under test (IUT). From the observations made during testing, we are then able to infer whether the IUT conforms to its specification. We study how partner services need to be designed to serve conformance testing in an asynchronous setting and present an algorithm which generates a complete test suite.

Kathrin Kaschner
Programming Services with Correlation Sets

Correlation sets define a powerful mechanism for routing incoming communications to the correct running session within a server, by inspecting the content of the received messages. We present a language for programming services based on correlation sets taking into account key aspects of service-oriented systems, such as distribution, loose coupling, open-endedness and integration. Distinguishing features of our approach are the notion of correlation aliases and an asynchronous communication model. Our language is equipped with formal syntax, semantics, and a typing system for ensuring desirable properties of programs with respect to correlation sets. We provide an implementation as an extension of the JOLIE language and apply it to a nontrivial real-world example of a fully-functional distributed user authentication system.

Fabrizio Montesi, Marco Carbone
Verification of Deployed Artifact Systems via Data Abstraction

Artifact systems are a novel paradigm for specifying and implementing business processes described in terms of interacting modules called

artifacts

. Artifacts consist of

data

and

lifecycle

models, accounting for the relational structure of the artifact state and its possible evolutions over time. We consider the problem of verifying artifact systems against specifications expressed in quantified temporal logic. This problem is in general undecidable. However, when artifact systems are deployed, their states can contain only a bounded number of elements. We exploit this fact to develop an abstraction technique that enables us to verify deployed artifact systems by model checking their bounded abstraction.

Francesco Belardinelli, Alessio Lomuscio, Fabio Patrizi

XaaS Computing

Profiling-as-a-Service: Adaptive Scalable Resource Profiling for the Cloud in the Cloud

Runtime profiling of Web-based applications and services is an effective method to aid in the provisioning of required resources, for monitoring service-level objectives, and for detecting implementation defects. Unfortunately, it is difficult to obtain accurate profile data on live client workloads due to the high overhead of instrumentation. This paper describes a cloud-based profiling service for managing the tradeoffs between: (i) profiling accuracy, (ii) performance overhead, and (iii) costs incurred for cloud computing platform usage. We validate our cloud-based profiling service by applying it to an open-source e-commerce Web application.

Nima Kaviani, Eric Wohlstadter, Rodger Lea
VM Placement in non-Homogeneous IaaS-Clouds

Infrastructure-as-a-Service (IaaS) cloud providers often combine different hardware components in an attempt to form a single infrastructure. This single infrastructure hides any underlying heterogeneity and complexity of the physical layer. Given a non-homogeneous hardware infrastructure, assigning

VM

s to physical machines (

PM

s) becomes a particularly challenging task.

VM

placement decisions have to take into account the operational conditions of the cloud (e.g., current

PM

load) and load balancing prospects through

VM

migrations. In this work, we propose a service realizing a two-phase

VM

-to-

PM

placement scheme. In the first phase, we identify a promising group of

PM

s, termed

cohort

, among the many choices that might be available; such a cohort hosts the virtual infrastructure of the user request. In the second phase, we determine the final

VM

-to-

PM

mapping considering all low-level constraints arising from the particular user requests and special characteristics of the selected cohort. Our evaluation shows that in large non-homogeneous physical infrastructures, we significantly reduce the

VM

placement plan production time and improve plan quality.

Konstantinos Tsakalozos, Mema Roussopoulos, Alex Delis

Service Discovery

Place Semantics into Context: Service Community Discovery from the WSDL Corpus

We propose a novel framework to automatically discover service communities that group together related services in a diverse and large scale service space. Community discovery is a key enabler to address a set of fundamental issues in service computing, which include service discovery, service composition, and quality-based service selection. The standard Web service description language, WSDL, primarily describes a service from the syntactic perspective and rarely provides rich service descriptions. This hinders the direct application of traditional document clustering approaches. In order to attack this central challenge, the proposed framework applies Non-negative Matrix Factorization (NMF) to the WSDL corpus for service community discovery. NMF has demonstrated its effectiveness in clustering high-dimensional sparse data while offering intuitive interpretability of the clustering result. NMF-based community discovery is further augmented via semantic extensions of the WSDL descriptions. The extended semantics are first computed based on the information sources outside the WSDL corpus. They are then seamlessly integrated with NMF, which makes the semantic extensions fit in the context of the original services. The experiments on real world Web services are presented to show the effectiveness of the proposed framework.

Qi Yu
WTCluster: Utilizing Tags for Web Services Clustering

Clustering web services would greatly boost the ability of web service search engine to retrieve relevant ones. An important restriction of traditional studies on web service clustering is that researchers focused on utilizing web services’ WSDL (Web Service Description Language) documents only. The singleness of data source limits the accuracy of clustering. Recently, web service search engines such as Seekda! allow users to manually annotate web services using so called tags, which describe the function of the web service or provide additional contextual and semantical information. In this paper, we propose a novel approach called

WTCluster

, in which both WSDL documents and tags are utilized for web service clustering. Furthermore, we present and evaluate two tag recommendation strategies to improve the performance of

WTCluster

. The comprehensive experiments based on a dataset consists of 15,968 real web services demonstrate the effectiveness of

WTCluster

and tag recommendation strategies.

Liang Chen, Liukai Hu, Zibin Zheng, Jian Wu, Jianwei Yin, Ying Li, Shuiguang Deng
Similarity Function Recommender Service Using Incremental User Knowledge Acquisition

Similar entity search is the task of identifying entities that most closely resemble a given entity (e.g., a person, a document, or an image). Although many techniques for estimating similarity have been proposed in the past, little work has been done on the question of which of the presented techniques are most suitable for a given similarity analysis task. Knowing the right similarity function is important as the task is highly domain- and data-dependent. In this paper, we propose a recommender service that suggests which similarity functions (e.g., edit distance or jaccard similarity) should be used for measuring the similarity between two entities. We introduce the notion of “similarity function recommendation rule” that captures user knowledge about similarity functions and their usage contexts. We also present an incremental knowledge acquisition technique for building and maintaining a set of similarity function recommendation rules.

Seung Hwan Ryu, Boualem Benatallah, Hye-Young Paik, Yang Sok Kim, Paul Compton
Revealing Hidden Relations among Web Services Using Business Process Knowledge

The wide spread of Service-oriented Computing and Cloud Computing has been increasing the number of web services on the Web. This increasing number of web services complicates the task of service discovery, in particular because of lack of rich service descriptions. Relations among web services are usually used to enhance service discovery. Formal service descriptions, logs of service invocations, or service compositions are typically used to find such relations. However, using such sources of knowledge enables finding simple relations only. In a previous work, we proposed to use business processes (BPs) to refine relations among web services used in the configurations of these BPs. That approach was limited to web services directly consumed by a

single

business process. In this paper, we generalize that approach and aim at predicting rich relations among web services that were not directly used together in any process configuration yet. To achieve this goal, we take all individual business processes (from a business process repository) and their configurations over web services (from a service registry) in the form of so-called extended behavioral profiles. These disparate profiles are then merged so that a single global profile is derived. Based on the aggregated knowledge in this global profile, we reveal part of the unknown relations among web services that have not been used together yet. We validate our approach through a set of experiments on a collection of business processes from SAP reference model.

Ahmed Awad, Mohammed AbuJarour

Service Science and Management

Towards a Service System Ontology for Service Science

Service Science is a new interdisciplinary approach to the study, design, implementation, and innovation of service systems. However due to the variety in service research, there is no consensus yet about the theoretical foundation of this domain. In this paper we clarify the service systems worldview proposed by Service Science researchers Spohrer and Kwan by investigating its foundational concepts from the perspective of established service theories and frameworks. By mapping the proposed service system concepts on the selected service theories and frameworks, we investigate their theoretical foundations, examine their proposed definitions and possible conflicting interpretations, discover their likely relationships and general structure, and identify a number of issues that need further discussion and elaboration. This analysis is visualised in a multi-view conceptual model (in the form of a UML class diagram) which we regard as a first step towards an explicitly and formally defined service system ontology.

Elisah Lemey, Geert Poels
Support for the Business Motivation Model in the WS-Policy4MASC Language and MiniZnMASC Middleware

The WS-Policy4MASC language and MiniZnMASC middleware for policy-driven management of service-oriented systems enable making IT system management decisions that maximize diverse business value metrics (e.g., profit, customer satisfaction). However, their past support for alignment with high-level business considerations was weak. Therefore, we introduce a new extension of WS-Policy4MASC that specifies the key concepts from the Business Motivation Model (BMM) industrial standard for modeling business intent. These concepts include hierarchies of ends (e.g., goals) and means (e.g., strategies). We also present and illustrate new decision making algorithms that leverage information in the extended WS-Policy4MASC to align run-time IT system management decisions with business considerations.

Qinghua Lu, Vladimir Tosic, Paul L. Bannerman
WS-Governance: A Policy Language for SOA Governance

The widespread use of Service Oriented Architectures (SOA) is beginning to create problems derived from the governance of said structures. To date there is not a single effective solution to solve all existing challenges to govern this type of infrastructure. This paper describes the problems encountered when designing a SOA governance solution in a real e-Government scenario. More specifically, we focus on problems related to specification and automated analysis of government policies. We propose a novel SOA governance specification model as a solution to these problems. We have named this model WS-Governance. In order to ease its adoption by SOA practitioners it: i) shares WS-Policy guidelines and is compatible with it, ii) has XML serialization as well as a plain-text one and iii) has a semantics based on a mapping to Constraint Satisfaction Problems that provides a precise description as well as facilitating the automation of some editing and WS-Governance related activities such as consistency checking.

José Antonio Parejo, Pablo Fernandez, Antonio Ruiz-Cortés
QoS-Based Task Scheduling in Crowdsourcing Environments

Crowdsourcing has emerged as an important paradigm in human-problem solving techniques on the Web. One application of crowdsourcing is to outsource certain tasks to the crowd that are difficult to implement as solutions based on software services only. Another benefit of crowdsourcing is the on-demand allocation of a flexible workforce. Businesses may outsource certain tasks to the crowd based on workload variations. The paper addresses the monitoring of crowd members’ characteristics and the effective use of monitored data to improve the quality of work. Here we propose the extensions of standards such as Web Service Level Agreement (WSLA) to settle quality guarantees between crowd consumers and the crowdsourcing platform. Based on negotiated agreements, we provide a skill-based crowd scheduling algorithm. We evaluate our approach through simulations.

Roman Khazankin, Harald Psaier, Daniel Schall, Schahram Dustdar

Service Security and Trust

Model Driven Security Analysis of IDaaS Protocols

Offloading user management functions like authentication and authorization to identity providers is a key enabler for cloud computing based services. Protocols used to provide identity as a service (IDaaS) are the foundation of security for many business transactions on the web and need to be thoroughly analyzed. While analysis of cryptographic protocols has been an active research area over the past three decades, the techniques have not been adapted to analyze security for complex web interactions. In this paper, we identify gaps in the area and propose means to address them. We extend an important belief logic (the so-called BAN logic) used for analyzing security in authentication protocols to support new concepts that are specific to browser based IDaaS protocols. We also address the problem of automating belief based security analysis through a UML based model driven approach which can be easily integrated with existing software engineering tools. We demonstrate benefits of the extended logic and model driven approach by analyzing two of the most commonly used IDaaS protocols.

Apurva Kumar
Credibility-Based Trust Management for Services in Cloud Environments

Trust management is one of the most challenging issues in the emerging cloud computing. Although many approaches have been proposed recently for trust management in cloud environments, not much attention has been given to determining the credibility of trust feedbacks. Moreover, the dynamic nature of cloud environments makes guaranteeing the availability of trust management services a difficult problem due to the unpredictable number of cloud consumers. In this paper, we propose a framework to improve ways on trust management in cloud environments. In particular, we introduce a credibility model that not only distinguishes between credible trust feedbacks, but also has the ability to detect the malicious trust feedbacks from attackers. We also present a replication determination model that dynamically decides the optimal replica number of the trust management service so that the trust management service can be always maintained at a desired availability level. The approaches have been validated by the prototype system and experimental results.

Talal H. Noor, Quan Z. Sheng

Service Monitoring

Monere: Monitoring of Service Compositions for Failure Diagnosis

Service-oriented computing has enabled developers to build large, cross-domain service compositions in a more routine manner. These systems inhabit complex, multi-tier operating environments that pose many challenges to their reliable operation. Unanticipated failures at runtime can be time-consuming to diagnose and may propagate across administrative boundaries. It has been argued that measuring readily available data about system operation can significantly increase the failure management capabilities of such systems. We have built an online monitoring system for cross-domain Web service compositions called Monere, which we use in a controlled experiment involving human operators in order to determine the effects of such an approach on diagnosis times for system-level failures. This paper gives an overview of how Monere is able to instrument relevant components across all layers of a service composition and to exploit the structure of BPEL workflows to obtain structural cross-domain dependency graphs. Our experiments reveal a reduction in diagnosis time of more than 20%. However, further analysis reveals this benefit to be dependent on certain conditions, which leads to insights about promising directions for effective support of failure diagnosis in large Web service compositions.

Bruno Wassermann, Wolfgang Emmerich
Multi-layered Monitoring and Adaptation

Service-based applications have become more and more multi-layered in nature, as we tend to build software as a service on top of infrastructure as a service. Most existing SOA monitoring and adaptation techniques address layer-specific issues. These techniques, if used in isolation, cannot deal with real-world domains, where changes in one layer often affect other layers, and information from multiple layers is essential in truly understanding problems and in developing comprehensive solutions.

In this paper we propose a framework that integrates layer specific monitoring and adaptation techniques, and enables multi-layered control loops in service-based systems. The proposed approach is evaluated on a medical imaging procedure for Computed Tomography (CT) Scans, an e-Health scenario characterized by strong dependencies between the software layer and infrastructural resources.

Sam Guinea, Gabor Kecskemeti, Annapaola Marconi, Branimir Wetzstein

Service Composition

Efficient, Interactive Recommendation of Mashup Composition Knowledge

In this paper, we approach the problem of interactively querying and recommending composition knowledge in the form of re-usable composition patterns. The goal is that of aiding developers in their composition task. We specifically focus on mashups and browser-based modeling tools, a domain that increasingly targets also people without profound programming experience. The problem is generally complex, in that we may need to match possibly complex patterns on-the-fly and in an approximate fashion. We describe an architecture and a pattern knowledge base that are distributed over client and server and a set of client-side search algorithms for the retrieval of step-by-step recommendations. The performance evaluation of our prototype implementation demonstrates that - if sensibly structured - even complex recommendations can be efficiently computed inside the client browser.

Soudip Roy Chowdhury, Florian Daniel, Fabio Casati
A Semantic and Information Retrieval Based Approach to Service Contract Selection

Service contracts represent the agreement between the service provider and potential service consumers to use a specific service under given conditions; for each service multiple service contracts are available. In this paper we investigate a new approach to support the service contract selection by exploiting preferences both explicitly defined by a user and implicitly inferred from his/her context. The core of our approach is the use of multi-constraint queries expressed on punctual values and on textual descriptions. Both semantic-based and information retrieval (IR) techniques are applied. Experimental evaluations show the effectiveness of the proposed approach.

Silvia Calegari, Marco Comerio, Andrea Maurino, Emanuele Panzeri, Gabriella Pasi
Modeling and Managing Variability in Process-Based Service Compositions

Variability in process-based service compositions needs to be explicitly modeled and managed in order to facilitate service/process customization and increase reuse in service/process development. While related work has been able to capture variability and variability dependencies within a composition, these approaches fail to capture variability dependenciesbetween the composition and partner services. Consequently, these approaches cannot address the situation when a composite service is orchestrated from partner services some of which are customizable. In this paper, we propose a feature-based approach that is able to effectively model variability within and across compositions. The approach is supported by a process development methodology that enables the systematic reuse and management of variability. We develop a prototype system supporting extended BPMN 2.0 to demonstrate the feasibility of our approach.

Tuan Nguyen, Alan Colman, Jun Han

Quality of Service 2

QoS-Driven Proactive Adaptation of Service Composition

Proactive adaptation of service composition has been recognized as a major research challenge for service-based systems. In this paper we describe an approach for proactive adaptation of service composition due to changes in service operation response time; or unavailability of operations, services, and providers. The approach is based on exponentially weighted moving average (EWMA) for modelling service operation response time. The prediction of problems and the need for adaptation consider a group of services in a composition flow, instead of isolated services. The decision of the service operations to be used to replace existing operations in a composition takes into account response time and cost values. A prototype tool has been implemented to illustrate and evaluate the approach. The paper also describes the results of a set of experiments that we have conducted to evaluate the work.

Rafael Aschoff, Andrea Zisman
A Quality Aggregation Model for Service-Oriented Software Product Lines Based on Variability and Composition Patterns

Quality evaluation is a challenging task in monolithic software systems. It is even more complex when it comes to Service-Oriented Software Product Lines (SOSPL), as it needs to analyze the attributes of a

family

of SOA systems. In SOSPL, variability can be planned and managed at the architectural level to develop a software product with the same set of functionalities but different degrees of non-functional quality attribute satisfaction. Therefore, architectural quality evaluation becomes crucial due to the fact that it allows for the examination of whether or not the final product satisfies and guarantees all the ranges of quality requirements within the envisioned scope. This paper addresses the open research problem of aggregating QoS attribute ranges with respect to architectural variability. Previous solutions for quality aggregation do not consider architectural variability for composite services. Our approach introduces variability patterns that can possibly occur at the architectural level of an SOSPL. We propose an aggregation model for QoS computation which takes both variability and composition patterns into account.

Bardia Mohabbati, Dragan Gašević, Marek Hatala, Mohsen Asadi, Ebrahim Bagheri, Marko Bošković
Optimization of Complex QoS-Aware Service Compositions

In Service-oriented Architectures, business processes can be realized by composing loosely coupled services. The problem of QoS-aware service composition is widely recognized in the literature. Existing approaches on computing an optimal solution to this problem tackle structured business processes, i.e., business processes which are composed of XOR-block, AND-block, and repeat loop orchestration components. As of yet, OR-block and unstructured orchestration components have not been sufficiently considered in the context of QoS-aware service composition. The work at hand addresses this shortcoming. An approach for computing an optimal solution to the service composition problem is proposed considering the structured orchestration components, such as AND/XOR/OR-block and repeat loop, as well as unstructured orchestration components.

Dieter Schuller, Artem Polyvyanyy, Luciano García-Bañuelos, Stefan Schulte

Research Papers – Short

Business Process Modeling

Goal-Driven Business Process Derivation

Solutions to the problem of deriving business processes from goals are critical in addressing a variety of challenges facing the services and business process management community, and in particular, the challenge of quickly generating large numbers of effective process designs (often a bottleneck in industry-scale deployment of BPM). The problem is similar to the planning problem that has been extensively studied in the artificial intelligence (AI) community. However, the direct application of AI planning techniques places an onerous burden on the analyst, and has proven to be difficult in practice. We propose a practical yet rigorous (semi-automated) algorithm for business process derivation from goals. Our approach relies on being able to decompose process goals to a more refined collection of sub-goals whose ontology is aligned with that of the effects of available tasks which can be used to construct the business process. Once process goals are refined to this level, we are able to generate a process design using a procedure that leverages our earlier work on semantic effect annotation of process designs. We illustrate our ideas throughout this paper with a real-life running example, and also present a proof-of-concept prototype implementation.

Aditya K. Ghose, Nanjangud C. Narendra, Karthikeyan Ponnalagu, Anurag Panda, Atul Gohad
Defining and Analysing Resource Assignments in Business Processes with RAL

Business process (BP) modelling notations tend to stray their attention from (human) resource management, unlike other aspects such as control flow or even data flow. They not only offer little intuitive languages to assign resources to BP activities, but neither link BPs with the structure of the organization where they are used, so BP models can easily contain errors such as the assignment of resources that do not belong to the organizational model. In this paper we address this problem and define RAL (Resource Assignment Language), a domain-specific language explicitly developed to assign resources to the activities of a BP model. RAL makes BPs aware of organizational structures. Besides, RAL semantics is based on an OWL-DL ontology, which enables the automatic analysis of resource assignment expressions, thus allowing the extraction of information from the resource assignments, and the detection of inconsistencies and assignment conflicts.

Cristina Cabanillas, Manuel Resinas, Antonio Ruiz-Cortés
Stochastic Optimization for Adaptive Labor Staffing in Service Systems

Service systems are labor intensive. Further, the workload tends to vary greatly with time. Adapting the staffing levels to the workloads in such systems is nontrivial due to a large number of parameters and operational variations, but crucial for business objectives such as minimal labor inventory. One of the central challenges is to optimize the staffing while maintaining system steady-state and compliance to aggregate SLA constraints. We formulate this problem as a parametrized constrained Markov process and propose a novel stochastic optimization algorithm for solving it. Our algorithm is a multi-timescale stochastic approximation scheme that incorporates a SPSA based algorithm for ‘primal descent’ and couples it with a ‘dual ascent’ scheme for the Lagrange multipliers. We validate this optimization scheme on five real-life service systems and compare it with a state-of-the-art optimization tool-kit OptQuest. Being two orders of magnitude faster than OptQuest, our scheme is particularly suitable for adaptive labor staffing. Also, we observe that it guarantees convergence and finds better solutions than OptQuest in many cases.

L. A. Prashanth, H. L. Prasad, Nirmit Desai, Shalabh Bhatnagar, Gargi Dasgupta
Declarative Enhancement Framework for Business Processes

While Business Process Management (BPM) was designed to support rigid production processes, nowadays it is also at the core of more flexible business applications and has established itself firmly in the service world. Such a shift calls for new techniques. In this paper, we introduce a variability framework for BPM which utilizes temporal logic formalisms to represent the essence of a process, leaving other choices open for later customization or adaption. The goal is to solve two major issues of BPM: enhancing reusability and flexibility. Furthermore, by enriching the process modelling environment with graphical elements, the complications of temporal logic are hidden from the user.

Heerko Groefsema, Pavel Bulanov, Marco Aiello

XaaS Computing

RSCMap: Resiliency Planning in Storage Clouds

Clouds use economies of scale to host data for diverse enterprises. However, enterprises differ in the requirements for their data. In this work, we investigate the problem of resiliency or disaster recovery (DR) planning in a cloud. The resiliency requirements vary greatly between different enterprises and also between different datasets for the same enterprise. We present in this paper Resilient Storage CloudMap (RSCMap), a generic cost-minimizing optimization framework for disaster recovery planning, where the cost functionmay be tailored tomeet diverse objectives.We present fast algorithms that come up with a minimumcost DR plan, while meeting all the DR requirements associated with all the datasets hosted on the storage cloud. Our algorithms have strong theoretical properties: 2 factor approximation for bandwidthminimization and fixed parameter constant approximation for the general cost minimization problem. We perform a comprehensive experimental evaluation of RSCMap using models for a wide variety of replication solutions and show that RSCMap outperforms existing resiliency planning approaches.

Vimmi Jaiswal, Aritra Sen, Akshat Verma
Dynamically Selecting Composition Algorithms for Economical Composition as a Service

Various algorithms have been proposed for the problem of quality-driven service composition. They differ by the quality of the resulting executable processes and by their processing costs. In this paper, we study the problem of service composition from an economical point of view and adopt the perspective of a Composition as a Service provider. Our goal is to minimize composition costs while delivering executable workflows of a specified average quality. We propose to dynamically select different composition algorithms for different workflow templates based upon template structure and workflow priority. For evaluating our selection algorithm, we consider two classic approaches to quality-driven composition, genetic algorithms and integer linear programming with different parameter settings. An extensive experimental evaluation shows significant gains in efficiency when dynamically selecting between different composition algorithms instead of using only one algorithm.

Immanuel Trummer, Boi Faltings
A Service Model for Development and Test Clouds

A Development & Test Cloud (DTC) enables IT service enterprises to host standardized configurations of just about any tool-set on cloud – the hosted software need not be designed for multi-tenancy and they may come from a multitude of vendors. However, since most enterprise software are available only under perpetual licenses, DTCs cannot become truly pay-per-use – customers of a DTC have to upfront purchase software licenses. This paper proposes a service model for a DTC vendor wherein the vendor purchases software licenses and recovers the cost from its clients based on their period of usage. Our model allows the vendor to maximize returns from a purchased license by using it in multiple projects separated in time. We set up an optimization problem to decide how best a DTC operator can invest in buying software licenses such that it gets maximum opportunity to resale purchased licenses. We conduct empirical studies to validate the feasibility and usefulness of our approach. Also, we enlist characteristics of tool-sets that make them profitable for the DTC vendor.

Debdoot Mukherjee, Monika Gupta, Vibha Singhal Sinha, Nianjun Zhou

Quality of Service

Time Based QoS Modeling and Prediction for Web Services

Quality of Service (QoS) prediction and aggregation for composite services is one of the key issues in service computing. Existing solutions model service QoSs either as deterministic values or probabilistic distributions. However, these works overlooked an important aspect in QoS modeling,

time

. Most QoS metrics, such as response time, availability, are time-dependent. We believe time variation should be explicitly reflected in QoS modeling as well as aggregation. In this paper, we propose a dynamic web service QoS model to capture the time based QoS patterns, based on which QoS of composite services are aggregated.

Leilei Chen, Jian Yang, Liang Zhang
CANPRO: A Conflict-Aware Protocol for Negotiation of Cloud Resources and Services

In a Cloud environment, users face the challenge of selecting and composing resources and services from a single or multiple providers. As several negotiations can occur concurrently, information on service and resource availability may be out-of-date, thus requiring several iterations between users and providers until an agreement is achieved. To address this problem, we introduce CANPRO, a Conflict-Aware Negotiation Protocol for allocating Cloud resource and services aimed at reducing cancellation messages during negotiation. CANPRO allows users (or entities on their behalf) to know the amount of resources being concurrently negotiated by other users and the number of users interested in such an amount, while still keeping users’ information private. By knowing this information, users can, for instance, confirm allocation requests with lower chances of having collisions with other users. In addition, for the same reason, users can increase their time deciding which (combination of) resources they want to allocate. The paper presents comparative results of CANPRO against the popular two-phase commit protocol (2PC) and a state-of-the-art protocol named SNAP-3PC. We used think time, network overhead, number of concurrent negotiations and providers as main metrics. The results are promising and the protocol can be used in scenarios other than Cloud Computing; for instance, bookings of health services, cars, tickets for venues, schedule of appointments, among others.

Marco A. S. Netto
Game-Theoretic Analysis of a Web Services Collaborative Mechanism

Web services are business applications having the capability to cooperate within groups to increase the efficiency of serving customers. There have been a number of proposed frameworks aggregating web services for the purpose of enhancing their capabilities with respect to providing the required service. However, the grouping procedure has got less attention. In this paper, we discuss the mechanism web services can use to join existing groups of web services (known as communities). Moreover, we analyze the scenarios where the community is filled up with web services that lied about their capabilities before joining. The objective is to provide and maintain a truthful environment where involving components act truthfully.

Babak Khosravifar, Jamal Bentahar, Kathleen Clacens, Christophe Goffart, Philippe Thiran
Importance Sampling of Probabilistic Contracts in Web Services

With web services quality of service (QoS) modeled as random variables, the accuracy of sampled values for precise service level agreements (SLAs) come into question. Samples with lower spread are more accurate for calculating contractual obligations, which is typically not the case for web services QoS. Moreover, the extreme values in case of heavy-tailed distributions (eg. 99.99 percentile) are seldom observed through limited sampling schemes. To improve the accuracy of contracts, we propose the use of variance reduction techniques such as importance sampling. We demonstrate this for contracts involving

demand

and

refuel

operations within the

Dell

supply chain example. Using measured values, efficient forecasting of future deviation of contracts may also be performed. A consequence of this is a more precise definition of sampling, measurement and variance tolerance in SLA declarations.

Ajay Kattepur
Particle Filtering Based Availability Prediction for Web Services

Guaranteeing the availability of Web services is a significant challenge due to unpredictable number of invocation requests the Web services have to handle at a time, as well as the dynamic nature of the Web. The issue becomes even more challenging for composite Web services in the sense that their availability is inevitably affected by corresponding component Web services. Current Quality of Service (QoS)-based selection solutions assume that the QoS of Web services (such as availability) is readily accessible and services with better availability are selected in the composition. Unfortunately, how to real-time maintain the availability information of Web services is largely overlooked. In addition, the performance of these approaches will become questionable when the pool of Web services is large. In this paper, we tackle these problems by exploiting particle filtering-based techniques. In particular, we have developed algorithms to precisely predict the availability of Web services and dynamically maintain a subset of Web services with higher availability. Web services can be always selected from this smaller space, thereby ensuring good performance in service compositions. Our implementation and experimental study demonstrate the feasibility and benefits of the proposed approach.

Lina Yao, Quan Z. Sheng
A Penalty-Based Approach for QoS Dissatisfaction Using Fuzzy Rules

Quality of Service (QoS) guarantees are commonly defined in Service Level Agreements (SLAs) between provider and consumer of services. Such guarantees are often violated due to various reasons. QoS violation requires a service adaptation and penalties have to be associated when promises are not met. However, there is a lack of research in defining and assessing penalties according to the degree of violation. In this paper, we provide an approach based on fuzzy logic for modelling and measuring penalties with respect to the extent of QoS violation. Penalties are assigned by means of fuzzy rules.

Barbara Pernici, S. Hossein Siadat, Salima Benbernou, Mourad Ouziri

Service Runtime Infrastructures

Cellular Differentiation-Based Service Adaptation

This paper proposes an approach to adapting services in a distributed system whose computational resources are dynamically changed. It supports the notions of cellular differentiation and dedifferentiation. When a service delegates a function to another component coordinating with it, if the former has the function, this function becomes less-developed and the latter’s function becomes well-developed. When some differentiated services are not available, it enables remaining services to automatically support the functions provided from the unavailable services. The approach was constructed as a middleware system and allowed us to define agents as Java objects. We present several evaluations of the framework in a distributed system.

Ichiro Satoh
Graceful Interruption of Request-Response Service Interactions

Bi-directional request-response interaction is a standard communication pattern in Service Oriented Computing (SOC). Such a pattern should be interrupted in case of faults. In the literature, different approaches have been considered: WS-BPEL discards the response, while Jolie waits for it in order to allow the fault handler to appropriately close the conversation with the remote service. We investigate an intermediate approach in which it is not necessary for the fault handler to wait for the response, but it is still possible on response arrival to gracefully close the conversation with the remote service.

Mila Dalla Preda, Maurizio Gabbrielli, Ivan Lanese, Jacopo Mauro, Gianluigi Zavattaro
Adaptation of Web Service Interactions Using Complex Event Processing Patterns

Differences in Web Service interfaces can be classified as signature or protocol incompatibilities, and techniques exist to resolve one or the other of these issues but rarely both. This paper describes

complex event processing

approach to resolving both signature and protocol incompatibilities existing between Web Service interfaces. The solution uses a small set of operators that can be applied to incoming messages individually or in combination to modify the structure, type and number of messages sent to the destination. The paper describes how CEP-based adapters, deployable in CEP engines, can be generated from automata representations of the operators through a standard process and presents a proof-of-concept implementation.

Yéhia Taher, Michael Parkin, Mike P. Papazoglou, Willem-Jan van den Heuvel

Service Migration and Adoption

Employing Dynamic Object Offloading as a Design Breakthrough for SOA Adoption

In several application contexts, Web Services adoption is limited due to performance issues. Design methods and migration strategies from legacy systems often propose the adoption of coarse-grained interfaces to reduce the number of interactions between clients and servers. This is an important design concern since marshaling and transferring small parts of complex business objects might entail sensible delays, especially in high latency networks. Nevertheless, transferring large data in coarse-grained interactions might bring useless data on the client side, whereas a small part of the transferred object is actually used.

This paper presents a novel approach to extend existing Web services run-time supports with dynamic offloading capabilities based on an adaptive strategy that allows servers to learn clients behaviors at runtime. By exploiting this approach, service based applications can improve their performances, as experimental results show, without any invasive change to existing Web services and clients.

Quirino Zagarese, Gerardo Canfora, Eugenio Zimeo
A Survey of SOA Migration in Industry

Migration of legacy software to service-based systems is an increasingly important problem area. So far, many SOA migration approaches have been proposed in both industry and academia. There is, however, considerable difference between SOA migration approaches defined in academia and those emerged in industry. This difference pinpoints a potential gap between theory and practice. To bridge this gap, we conducted an industrial interview survey in seven leading SOA solution provider companies. Results have been analyzed with respect to migration activities, the available knowledge assets and the migration process. In addition, industrial approaches have been contrasted with academic ones, hence discussing differences and promising directions for industry-relevant research. As a result we found that, in fact, all companies converge to the same, one, common SOA migration approach. This suggests that, with experience, enterprises mature toward a similar approach to SOA migration.

Maryam Razavian, Patricia Lago

Service Composition

Forms-based Service Composition

In many cases, it is not cost effective to automate business processes which affect a small number of people and/or change frequently. We present a novel approach for enabling domain experts to model and deploy such processes from their respective domain as Web service compositions. The approach is based on user-editable service naming, a graphical composition language where Web services are represented as forms, a targeted restriction of control flow expressivity, automated process verification mechanisms, and code generation for executing orchestrations. A Web-based service composition prototype implements this approach, including a WS-BPEL code generator.

Ingo Weber, Hye-Young Paik, Boualem Benatallah
Contractually Compliant Service Compositions

In the field of service-oriented computing, an e-contract is used to regulate the acceptable behaviours of the services taking part in a composition.

C-O Diagrams

are a visual model for the specification of deontic e-contracts, including reparations, conditional clauses and real-time restrictions. In this work we define a set of satisfaction rules based on timed automata to see whether a composition is compliant with the contract specification, providing the model with the mathematical rigour necessary for formal verification.

Enrique Martínez, Gregorio Díaz, M. Emilia Cambronero
Profit Sharing in Service Composition

Component services are often provided by different organizations, which needs to determine how to divide the profit obtained for the composite service to the component service providers. Previous studies have mainly focused on the process of aggregating multiple component services into a composite service. However, the process of the profit sharing has not yet discussed sufficiently. This problem can be formalized as a coalition game in the game theory. However, its flexibility of defining the policy of utilizing the services causes a problem. This paper shows that the existing profit sharing methods, more precisely, neither the equal division method nor the division method based on the Shapley value cannot satisfy the following two desiderata; (1) the sufficient level of service provision is attained, and (2) component services are not broken up more than is necessary. Moreover, we examine what factors make difficult to attain the sufficient level of service provision, and give a discussion toward mitigating this problem.

Shigeo Matsubara

Service Applications

A Predictive Business Agility Model for Service Oriented Architectures

Service-Oriented Architecture (SOA) is now considered a mainstream option for delivering solutions that promise business agility benefits. Unfortunately, there is currently no quantitative approach for predicting the expected agility of a SOA system under development. In this paper we present an empirically validated Predicted Business Agility Index (PBAI) which is designed to measure the expected business agility of a SOA deployment. The PBAI is constructed through statistically analyzing the relationship between 150 technical attributes and the attainment of business agility in 39 SOA deployments. 37 of the technical attributes, classified into three areas of architecture, business process management, and impact analysis are determined to be the primary contributors to achieving business agility. The PBAI is evaluated using a leave-one-out cross validation experiment of the SOA projects in our study.

Mamoun Hirzalla, Peter Bahrs, Jane Cleland-Huang, Craig S. Miller, Rob High
Personal-Hosting RESTful Web Services for Social Network Based Recommendation

Recommender systems have been widely used in information filtering. However the existing recommendation methods do not work effectively in the situations when a group of people want to share information and make recommendations within a social network. In this paper we propose a personal-hosting web services architecture

ph-REST

for social network based recommendation, in which every user is represented by a dedicated RESTful web services engine that collaborates with others over a social structure formed by

co-peers with common interests

. The proposed architecture explores the potential of applying service and Cloud computing to personal and social information sharing and assimilation.

Youliang Zhong, Weiliang Zhao, Jian Yang
Work as a Service

Improving work within and among enterprises is of pressing importance. We take a services-oriented view of both doing and coordinating work by treating

work as a service

. We discuss how large work engagements can be decomposed into a set of smaller interconnected service requests and conversely how larger engagements can be built up from smaller ones. Encapsulating units of work into service requests enables assignment to any organization qualified to service the work, and naturally lends itself to ongoing optimization of the overall engagement.

A service request contains two distinct parts: coordination information for coordinating work and payload information for doing work. Coordination information deals with business concerns such as risk, cost, schedule, and value co-creation. On the other hand, payload information defines the deliverables and provides what is needed to do the work, such as designs or use-cases. This general two-part decomposition leads to a paradigm of work as a two-way information flow between service systems, rather than as a business process that needs to be implemented or integrated between two organizations.

Treating work as information flow allows us to leverage extant understanding of information systems and facilitates information technology support for work using mainstream service-oriented architectures (SOA). Significant benefits from this approach include agility in setting up large engagements to be carried out by distributed organizations, visibility into operations without violating providers’ privacy or requiring changes to internal processes, responsiveness to unpredictability and change, and ongoing optimizations over competing business objectives.

Daniel V. Oppenheim, Lav R. Varshney, Yi-Min Chee
Backmatter
Metadaten
Titel
Service-Oriented Computing
herausgegeben von
Gerti Kappel
Zakaria Maamar
Hamid R. Motahari-Nezhad
Copyright-Jahr
2011
Verlag
Springer Berlin Heidelberg
Electronic ISBN
978-3-642-25535-9
Print ISBN
978-3-642-25534-2
DOI
https://doi.org/10.1007/978-3-642-25535-9