Service-oriented computing: a research roadmap

TL;DR: Service-Oriented Computing (SOC) is a new computing paradigm that utilizes services as the basic constructs to support the development of rapid, low-cost and easy composition of distributed applications even in heterogeneous environments.

Abstract: Service-Oriented Computing (SOC) is a new computing paradigm that utilizes services as the basic constructs to support the development of rapid, low-cost and easy composition of distributed applications even in heterogeneous environments. The promise of Service-Oriented Computing is a world of cooperating services where application components are assembled with little effort into a network of services that can be loosely coupled to create flexible dynamic business processes and agile applications that may span organizations and computing platforms. The subject of Service-Oriented Computing is vast and enormously complex, spanning many concepts and technologies that find their origins in diverse disciplines that are woven together in an intricate manner. In addition, there is a need to merge technology with an understanding of business processes and organizational structures, a combination of recognizing an enterprise's pain points and the potential solutions that can be applied to correct them. The materi...

Summary

Introduction

• Each theme is introduced briefly from a technology, state of the art and scientific challenges standpoint.
• Several of these obstacles arise due to the current lack of interdisciplinary research in the field, which is considered to be a major impediment that limits added economic growth through deployment and use of services technology.
• These are long-term visions that serve as integration platforms and demonstrators for an holistic approach to Service Oriented Computing in the identified key areas.

1. Overview

• Today’s business climate demands a high rate of change with which Information Technology (IT)-minded organizations are required to cope.
• All of these situations and more drive the need for the IT infrastructure of an organization to respond quickly in support of new business models and requirements.
• Services reflect a "service-oriented" approach to programming, based on the idea of composing applications by discovering and invoking network-available services rather than building new applications or by invoking available applications to accomplish some task [Papazoglou 2003].
• They have to specialize and develop their individual strengths to remain competitive.
• A wellconstructed, standards-based Service Oriented Architecture can empower a business environment with a flexible infrastructure and processing environment.

2. Need for a Services Research Roadmap

• As Service Oriented Computing is very much an emerging field, there is no such thing as a “general audience” for Service Oriented Computing -- there are many people (researchers and practitioners) with many different (and probably conflicting) levels of understanding and uses for Service Oriented Computing.
• The material in research spans an immense and diverse spectrum of literature, in origin and in character.
• As a result research activities are very fragmented and do not contribute to a mutually acceptable, joint research agenda.
• This will further enhance the value proposition of SOC and will facilitate the formulation of a Services Research Roadmap leading to more effective and clearly inter-related solutions and better exploitation of research results.
• These experts have repeatedly met during the past three years at the International Conference on Service Oriented Computing (see icsoc.org) at workshops and Dagstuhl seminar series meetings (see © The authors - 5 - 19 April 2006 http://www.dagstuhl.de/05462/ and http://www.dagstuhl.de/06291/) and on other separate occasions.

3. Research Roadmap for Service Oriented Computing Research

• Services Research Roadmap introduces a stratified logical service-based architecture (known as extended Service Oriented Architecture [Papazoglou 2003], [Papazoglou 2005a]) to create a reactive and adaptive IT environment.
• As shown in Figure 1, the Services Research Roadmap has three planes with the bottom plane utilizing the basic service middleware and architectural constructs and functionality for describing, publishing and discovering services, while the service composition and management planes are layered on top of it.
• The perpendicular axis indicates service characteristics that cut across all three planes.
• While traditional QoS metrics apply, the characteristics of Web services environments bring both greater availability of applications and increased complexity in terms of accessing and managing services and thus impose specific and intense demands on organisations, which QoS must address.
• Finally, Figure 1 illustrates that service modelling and service oriented engineering, i.e., service oriented analysis, design and development techniques and methodologies, are crucial elements for the developing meaningful services and business process specifications and an important requirement for SOA applications that leverage Web services.

3.1 Service Foundations

• The bottom plane in the Services Research Roadmap is the service foundations plane that provides a service oriented middleware backbone that realizes the runtime SOA infrastructure that connects heterogeneous components and systems, and provides multiple-channel access to services, e.g., via mobile devices, hand held devices, over variety of networks including the Internet, cable, UMTS, XDSL, Bluetooth, and so on.
• This runtime infrastructure allows defining basic interactions involving the description, publishing, finding and binding of services.
• The service provider defines a service description of the service and publishes it to a client (or service discovery agency) through which a service description is published and made discoverable.
• Service provider and service client roles are logical constructs and a service may exhibit characteristics of both.
• In Figure 1 service aggregators group services that are provided by other service providers into a distinct value added service and may themselves act as service providers.

3.1.1 State of the Art

• The requirements to provide an appropriately capable and manageable integration infrastructure for Web services and SOA are coalescing into the concept of the Enterprise Service Bus (ESB).
• An ESB is a set of infrastructure capabilities implemented by middleware technology that enable an SOA and alleviate disparity problems between applications running on heterogeneous platforms and using diverse data formats.
• There is a “container” for the service implementation taking care of exposing the service functionalities and non-functional properties to the external world via the network.
• Service specific architectures that are designed for particular classes of services/applications [L´opez 2001], [Liu 2002], [Poladian 2004].
• Such activities target the use of formal languages for semantically describing all relevant aspects of Web services in order to facili- ©.

3.1.2 Grand Challenges

• The run-time service infrastructure should be able to configure itself and be optimized automatically in accordance with specific application requirements and high-level policies — representing business-level objectives, for example—that specify what is desired (such as particular security and privacy requirements) and not how it is to be accomplished.
• Topic and content-based routing capabilities: Infrastructure support for application integration: Improving service discovery requires explicating the semantics of both the service provider and the service requester.

3.2 Service Composition

• The service composition plane in the Services Research Roadmap encompasses necessary roles and functionality for the aggregation of multiple services into a single composite service.
• Service aggregators thus become service providers by publishing the service descriptions of the composite service they create.
• Service aggregators perform service coordination to control the execution of the composite services (viz. processes), services transactions and manage both the dataflow as well as the control flow between composite services.
• They also enforce policies on aggregate service invocations.

3.2.1 State of the Art

• The full potential of Web services as a means of developing dynamic e-Business solutions will only be realised when applications and business processes are able to integrate their complex interactions into composite added value services.
• When looking at Web services, for example, it is important to differentiate between the baseline specifications of SOAP, UDDI and WSDL that provide the infrastructure that supports publishing, finding and binding operations in the service-oriented architecture and higher-level specifications required for e-Business integration.
• Orchestration describes how services can interact with each other at the message level, including the business logic and execution order of the interactions from the perspective and under control of a single endpoint.
• Choreography offers a means by which the rules of participation for collaboration can be clearly defined and agreed to, jointly.
• Many of the existing approaches towards service composition largely neglect the context in which composition takes place.

3.2.2 Grand Challenges

• One of the major challenges for industry-wide adoption of the service-oriented approach is the automated composition of distributed business processes, i.e. the development of technology, methods and tools that support an effective, flexible, reliable, easy-to-use, low-cost, dynamic, time-efficient composition of electronic distributed business processes.
• So far, the automated composition of distributed business processes is still far from being achieved: no effective, easy-to-use, flexible support is provided that can cope with the life cycle of distributed business processes, with their inevitable evolution and required adaptation to changes in, e.g., business strategies and markets, customers and providers relationships, interactions, and so on.
• The result, the shared knowledge and the interoperable processes, the common models and objectives, are not known a priori, they emerge from a distributed negotiation process where each actor accepts to give up some of its assets, if this is compensated by some advantage due to being part of a network.
• Moreover, the client must determine if the service should communicate using signed messages.
• According to this view, service composition at the business level should pose the requirements and the boundaries for the automatic composition at the system level.

3.3 Service Management and Monitoring

• Composite service developments necessitate the use of mechanisms that provide them insights into the health of systems that implement Web services and into the status and behaviour patterns of loosely coupled applications.
• Failure or change of a single application component can bring down numerous interdependent enterprise applications.
• Application performance depends on the combined performance of cooperating components and their interactions.
• The rationale is very similar to the situation in traditional distributed computing environments, where systems administrators rely on programs/tools/utilities to make certain that a distributed computing environment operates reliably and efficiently.
• Service management spans a range of activities from installation and configuration to collecting metrics and tuning to ensure responsive service execution.

3.3.1 State of the Art

• Services Research Roadmap's service operations management typically gathers information about the managed service platform, services and business processes and managed resource status and performance, and supporting specific management tasks (e.g., root cause failure analysis, SLA monitoring and reporting, service deployment, and life cycle management and capacity planning).
• Finally, service operations management also provides global visibility of running processes, comparable to that provided by Business Process Management tools.
• Such activities are the target of the Web Services Distributed Management (WSDM) specification.
• The finer grained nature of services (as opposed to applications) requires evaluating processes and transactions at a more magnified rate and in a more contextually aware manner.
• This environment demands that contracts are set up, stipulating agreements between services regarding their collaboration, both at the functional and non-functional level, in a concise manner.

3.3.2 Grand Challenges

• Seeding autonomic capabilities for service level management is an evolutionary service level management approach where autonomic computing capabilities anticipate IT system requirements and resolve problems, with minimal human intervention.
• Self-adapting management services —Self-adapting services adapt dynamically to changes in the environment, market and so on, using policies provided by the IT professional.
• Self-optimization helps provide a high standard of service for both the system’s end users and a business’s customers.
• Self-protecting services can anticipate, detect, identify and protect against threats.

3.4 Service Design and Development (Service Oriented Engineering)

• Service oriented applications start from the premise that all businesses have a business design.
• A business design describes how that business works – the processes that it performs; the organizational structure of the people and finances within that business; the business’ near-term and long-term goals and objectives; the economic and market influences that affect how that business achieves its goals; the rules and policies that condition how the business operates [Papazoglou 2006a].
• A well-constructed SOA can empower a business environment with a flexible infrastructure and processing environment by provisioning independent, reusable automated business processes (as services) and providing a robust foundation for leveraging these services.
• The authors - 20 - 19 April 2006 ary software engineering approach that partly builds upon earlier development processes including component-based development and business process modelling [Harmon 2003].
• While relatively simple Web services may be built that way, a service-based development methodology is of critical importance to specify, construct, refine and customize highly volatile business processes from internally and externally available Web services.

3.4.1 State of the Art

• A service-oriented design and development methodology focuses on business processes, which it considers as reusable elements that are independent of applications and the computing platforms on which they run.
• Conventional development methodologies such as Object-Oriented Development (OOD) and Component Based Development (CBD) do not address the three key elements of an SOA: services, service assemblies , and components realizing services.
• Activities have mainly concentrated on two fronts on developing a methodology for service-oriented engineering and on design-time models.
• If a developer makes a change to a service interface, all older requestors would fail, and the failure would be undetectable to the Web services infrastructure.
• The potential composition of services into business processes across organizational boundaries can function properly and efficiently only if the services are effectively governed for compliance to requirements dictated by QoS factors.

4. References

• [Ambite 2004] J. L. Ambite, et. al “Argos: An Ontology and Web Service Composition Infrastructure for Goods Movement Analysis”, National Conference on Digital Government Research, Seattle, Washington, May 2004.
• [Andrews 2003] T. Andrews et. al. (eds), “Business Process Execution Language for Web Services”, May 2003, available at http://www.ibm.com/developerworks/library/ws-bpel.
• “Evaluation of a Resource Selection Mechanism For Complex Network Services”, Proceedings of the Tenth IEEE International Symposium on High Performance Distributed Computing, Aug. 2001.
• “Semantic Matching of Web Services Capabilities”, 1st International Semantic Web Conference, 2002. [Papazoglou 2003] M.P. Papazoglou and G. Georgakapoulos, “Service-Oriented Computing, CACM”, October 2003, 46(10).

Figures

Figure 1: Research planes in the Services Research Roadmap

Table 1: Overview of state of the art and grand challenges in Services Research

Figure 4: The Web Services Development Life Cycle hierarchy

Figure 3: Web services management architecture

Figure 2: Enterprise service bus connecting diverse applications and technologies.

Full text

© The authors - 1 - 19 April 2006
Service-Oriented Computing
Research Roadmap
Michael P. Papazoglou
1
, Paolo Traverso
2
, Schahram Dustdar
3
,
Frank Leymann
4
, Bernd J. Krämer
5
Summary
Service-Oriented Computing (SOC) is a new computing paradigm that utilizes services as the basic
constructs to support the development of rapid, low-cost and easy composition of distributed applica-
tions even in heterogeneous environments. The visionary promise of Service-Oriented Computing is a
world of cooperating services where application components are assembled with little effort into a
network of services that can be loosely coupled to create flexible dynamic business processes and
agile applications that may span organisations and computing platforms. SOC is being shaped by, and
increasingly will help shape, modern society as a whole, especially in the areas of dynamic and on-
demand business and education, health and government services.
The subject of SOC is vast and enormously complex, spanning many concepts and technologies that
find their origins in diverse disciplines that are woven together in an intricate manner. In addition,
there is a need to merge technology with an understanding of business processes and organizational
structures, a combination of recognizing an enterprise's pain points and the potential solutions that
can be applied to correct them. The material in research spans an immense and diverse spectrum of
literature, in origin and in character. As a result research activities at both worldwide as well as at
European level are very fragmented. This necessitates that a broader vision and perspective be estab-
lished—one that permeates and transforms the fundamental requirements of complex applications
that require the use of the SOC paradigm. This will further enhance the value proposition of Service-
Oriented Computing and will facilitate the formulation of a Services Research Roadmap leading to
more effective and clearly inter-related solutions and better exploitation of research results.
This document provides the necessary background for deciding on potential future research pro-
grammes in SOC and places on-going research activities and projects in the broader context of a SOC
Roadmap. This research roadmap launches four pivotal, inherently related, research themes to SOC:
service foundations, service composition, service management and monitoring and service-oriented
engineering. The viewpoints presented in this document partly result from intensive discussions ex-
perts with various backgrounds led in parallel workgroup and in plenary sessions that took place dur-
ing the International Dagstuhl Seminar on Service-Oriented Computing held November 15-18, 2005,
in Schloss Dagstuhl, Wadern.
Each theme is introduced briefly from a technology, state of the art and scientific challenges stand-
point. From the technology standpoint a comprehensive review of state of the art, standards, and
current research activities in each key area is provided. From the state of the art the major open prob-
lems and bottlenecks to progress are identified. Several of these obstacles arise due to the current
lack of interdisciplinary research in the field, which is considered to be a major impediment that limits
added economic growth through deployment and use of services technology. Finally, the scientific
challenges that tackle the found obstacles are formulated. These are long-term visions that serve as
integration platforms and demonstrators for an holistic approach to Service Oriented Computing in the
identified key areas. These future research activities form a sound background for deciding on poten-
tial future programmes in SOC.
1
Tilburg University, Tilburg, The Netherlands, e-mail: mikep@uvt.nl.
2
Istituto per la Ricerca Scientifica e Tecnologica (IRST), Trento, Italy, e-mail: traverso@itc.it.
3
Technical University of Vienna, Vienna, Austria, e-mail: dustdar@infosys.tuwien.ac.at.
4
University of Stuttgart, Stuttgart, Germany, e-mail: Frank.Leymann@informatik.uni-stuttgart.de.
5
FernUniversität in Hagen, Hagen, Germany, e-mail: Bernd.Kraemer@Fernuni-Hagen.de
Dagstuhl Seminar Proceedings 05462
Service Oriented Computing (SOC)
http://drops.dagstuhl.de/opus/volltexte/2006/524

© The authors - 2 - 19 April 2006
Service-Oriented Computing Research Roadmap
1. Overview
Today’s business climate demands a high rate of change with which Information Technology
(IT)-minded organizations are required to cope. Organizations face rapidly changing market
conditions, new competitive pressures, new regulatory fiats that demand compliance, and
new competitive threats. All of these situations and more drive the need for the IT infra-
structure of an organization to respond quickly in support of new business models and re-
quirements. Only in this way can an organization gear towards the real world of fully auto-
mated, complex electronic transactions. As most enterprise applications were not designed
to enable rapid adaptation of application functionality, this adds another level of intricacy to
an already complex IT landscape. At the same time it increases infrastructure complexity
and limits its ability to quickly change application features or functions.
Integration and infrastructure management are the key elements of an on demand operat-
ing IT environment. Integration enables the efficient and flexible combination of resources
to optimize operations across and beyond the boundaries of an organization and enables
them to interoperate seamlessly. Integration is about seamlessly interlinking on one hand
people and on the other hand processes and information that may transcend organizational
boundaries despite the existence of multiple - and possibly heterogeneous - platforms and
protocols, and numerous access devices, while leveraging the potential of the Internet. In-
frastructure management address two objectives: automation and virtualization of the envi-
ronment. Automation of the environment is achieved by the capability to reduce manage-
ment complexity to enable better use of assets, improve availability and resiliency, and re-
duce costs based on business policy and objectives. Virtualization of the environment is
achieved by the capability to provide easy access to and a single consolidated view of all
available resources in a network—no matter where the resources or information reside.
Service orientation provides the underlying implementation that can make an on demand IT
operating environment a reality by supporting the functions of both integration and infra-
structure management [Lymann 2005a].
Service-Oriented Computing (SOC) utilizes services as the constructs to support the devel-
opment of rapid, low-cost and easy composition of distributed applications. Services are
autonomous, platform-independent computational entities that can be used in a platform
independent way. Services can be described, published, discovered, and dynamically as-
sembled for developing massively distributed, interoperable, evolvable systems. Services
perform functions that can range from answering simple requests to executing sophisticated
business processes requiring peer-to-peer relationships between possibly multiple layers of
service consumers and providers. Any piece of code and any application component de-
ployed on a system can be reused and transformed into a network-available service. Serv-
ices reflect a "service-oriented" approach to programming, based on the idea of composing
applications by discovering and invoking network-available services rather than building new
applications or by invoking available applications to accomplish some task [Papazoglou
2003]. Services are most often built in a way that is independent of the context in which
they are used. This means that the service provider and the consumers are loosely coupled.
This "service-oriented" approach is independent of specific programming languages or oper-
ating systems. It allows organisations to expose their core competencies programmatically
over the Internet or a variety of networks, e.g., cable, UMTS, XDSL, Bluetooth, etc., using
standard (XML-based) languages and protocols, and implementing a self-describing inter-
face. Web Services are the current most promising technology based on the concept of
Service Oriented Computing [Weerawarana 2005]. Web services provide the basis for the

© The authors - 3 - 19 April 2006
development and execution of business processes that are distributed over the network and
available via standard interfaces and protocols. Web services may use the Internet as the
communication medium (as well as other transport protocols) and open Internet-based
standards, such as the Simple Object Access Protocol (SOAP) as transmission medium, the
Web Services Description Language (WSDL) for service definition and the Business Process
Execution Language (BPEL) for orchestrating services.
The visionary promise of services technologies is a world of cooperating services where ap-
plication components are assembled with little effort into a network of services that can be
loosely coupled to create dynamic business processes and agile applications that span orga-
nizations and computing platforms [Leymann 2005c]. Services hold the promise of moving
beyond the simple exchange of information – the dominating mechanism for application
integration today – to the concept of accessing, programming and integrating application
services that are encapsulated within old and new applications. An important economic
benefit of the Service Oriented Computing paradigm is that it enables application developers
to dynamically grow application portfolios more quickly than ever before, by creating com-
pound application solutions that use internally existing organisational software assets which
they appropriately combine with external components possibly residing in remote networks.
Previously isolated Enterprise Resource Planning (ERP), Customer Relationship Management
(CRM), Supply Chain Management (SCM), Human Resource Management (HRM), financial,
and other legacy systems can now be converted to service enabled architectures and inte-
grated more effectively than when relying on custom, point-to-point coding or proprietary
Enterprise Application Integration technology. The end result is that it is then easier to cre-
ate new composite applications that use pieces of application logic and/or data that reside in
the existing systems. This represents a fundamental change to the socio-economic fabric of
the software developer community that improves the effectiveness and productivity in soft-
ware development activities and enables enterprises to bring new products and services to
the market more rapidly [Leymann 2003].
Service technology will also become the backbone of systems and processes of more and
more educational organizations. Governmental committees and organizations like CETIS
(Centre for Educational Technology Interoperability Standards) in the UK or the Australian
Department of Education have teamed up with major US universities to promote service-
oriented framework concepts and standards in e-learning systems [Wilson 2005]. To serve
the changing needs of the networked world, universities need to cooperate to reduce costs
while responding to the growing demand. They have to specialize and develop their individ-
ual strengths to remain competitive. They must provide pervasive and personalized tech-
nologies and services. They need to integrate their abundance of learning resources and
teaching competencies to compensate individual weaknesses and jointly succeed in the
emerging international education market. SOC technology promises to overcome the ex-
tremely heterogeneous landscape of e-university implementations and the current lack of
appropriate conceptual and technology standards that prohibit the seamless integration of
university portal services to enable cross-institutional cooperation including the possibility of
virtual mobility of students and academic staff [Krämer 2006].
Key to this concept is the service-oriented architecture (SOA). SOA is a logical way of de-
signing a software system to provide services to either end-user applications or to other
services distributed in a network, via published and discoverable interfaces. A well-
constructed, standards-based Service Oriented Architecture can empower a business envi-
ronment with a flexible infrastructure and processing environment. SOA achieves this by
provisioning independent, reusable automated business process and systems functions as
services and providing a robust and secure foundation for leveraging these services. Effi-
ciencies in the design, implementation, and operation of SOA-based systems can allow or-
ganizations to adapt far more readily to a changing environment.

© The authors - 4 - 19 April 2006
Services technologies are being shaped by, and increasingly will help shape, modern society
as a whole, especially in vital areas such as dynamic business, health, education and gov-
ernment services. Applying services technologies leads to reduced complexity and costs,
exposing and reusing core business functionality, increased flexibility, resilience to technol-
ogy shifts and improving operational efficiency. For all these reasons, it is expected that the
Service Oriented Computing paradigm will exhibit a steeper adoption curve, as it solves ex-
pensive and intractable business and technology problems, and will infiltrate more of the
applications portfolio, than previous application technologies.
2. Need for a Services Research Roadmap
As Service Oriented Computing is very much an emerging field, there is no such thing as a
“general audience” for Service Oriented Computing -- there are many people (researchers
and practitioners) with many different (and probably conflicting) levels of understanding and
uses for Service Oriented Computing.
The subject of Service Oriented Computing is vast and enormously complex, spanning many
concepts, protocols and technologies that find their origins in disciplines such as distributed
computing systems, computer networking, computer architectures and middleware, grid
computing, software engineering, programming languages, database systems, security, ar-
tificial intelligence and knowledge representation that are interwoven in an intricate manner.
In addition there is a need to merge technology with an understanding of business proc-
esses and organization structures, a combination of recognizing an enterprise's pain points
and the potential solutions that can be applied to correct them. The material in research
spans an immense and diverse spectrum of literature, in origin and in character. As a result
research activities are very fragmented and do not contribute to a mutually acceptable, joint
research agenda.
Only through adaptation of an holistic approach to Service Oriented Computing research it is
considered likely that new industries and economic growth factors can be provided. Thus to
unleash the full potential of SOC research a broader vision and perspective is required—one
that permeates and transforms the fundamental requirements of complex applications that
require the use of the Service-Oriented Computing paradigm. This will further enhance the
value proposition of SOC and will facilitate the formulation of a Services Research Roadmap
leading to more effective and clearly inter-related solutions and better exploitation of re-
search results.
Purpose of the Services Research Roadmap is to facilitate efficient and effective use of re-
search funds by consolidating, streamlining and strategically inter-relating the current re-
search results and agenda and prioritizing attention to gaps, encouraging interdisciplinary
research that might otherwise be overlooked, and coordinating existing and future research
work and projects. This will overcome the present fragmentation of Europe’s research ef-
forts in the area of service-oriented computing by establishing a common research agenda,
ensuring consolidation, as well as integration and exploitation of research results from
European research initiatives. Its aim is to achieve visibility and exploitation of research
results at a global scale both throughout Europe and internationally.
The Services Research Roadmap that is described in Section 3 was built using advice pro-
vided by panels of experts representing many disciplines including distributed computing,
database and information systems, software engineering and design, computer architec-
tures and middleware and knowledge representation. These experts have repeatedly met
during the past three years at the International Conference on Service Oriented Computing
(ICSOC) (see icsoc.org) at workshops and Dagstuhl seminar series meetings (see

© The authors - 5 - 19 April 2006
http://www.dagstuhl.de/05462/ and http://www.dagstuhl.de/06291/) and on other sepa-
rate occasions.
3. Research Roadmap for Service Oriented Computing Research
Services Research Roadmap introduces a stratified logical service-based architecture
(known as extended Service Oriented Architecture [Papazoglou 2003], [Papazoglou 2005a])
to create a reactive and adaptive IT environment. This environment has the ability to repre-
sent detailed business policies and rules abstracted from fixed functional and operational
capabilities and delivering these abstracted capabilities in the form of customizable service-
oriented solutions. Its objective is to provide facilities for ensuring consistency across the
organization, high availability of services, security of non-public services and information,
orchestration of multiple services as part of mission-critical composite applications – all es-
sential requirements for business-quality services. Thus it strives to improve systems and
business visibility and provide greater control and flexibility in defining and adjusting busi-
ness rules and parameters.
The architectural layers in the Services Research Roadmap, which are depicted in Figure 1,
describe a logical separation of functionality in such a way that each layer defines a set of
constructs, roles and responsibilities and leans on constructs of its preceding layer to ac-
complish its mission. The logical separation of functionality is based on the need to separate
basic service capabilities provided by a services middleware infrastructure and conventional
SOA from more advanced service functionality needed for dynamically composing (integrat-
ing) services and the need to distinguish between the functionality for composing services
from that of the management of services and their underlying infrastructure.
As shown in Figure 1, the Services Research Roadmap has three planes with the bottom
plane utilizing the basic service middleware and architectural constructs and functionality for
describing, publishing and discovering services, while the service composition and manage-
ment planes are layered on top of it. The perpendicular axis indicates service characteristics
that cut across all three planes. These include semantics, non-functional service properties
and Quality of Service (QoS). As cross cutting concerns permeate all three planes (see Fig-
ure 1) we shall introduce them briefly below before focussing on the Services Research
Roadmap planes in the following subsections.
Quality of Service encompasses important functional and non-functional service quality at-
tributes, such as performance metrics (response time, for instance), security attributes,
(transactional) integrity, reliability, scalability, and availability. Delivering QoS on the Inter-
net is a critical and significant challenge because of its dynamic and unpredictable nature.
Applications with very different characteristics and requirements compete for all kinds of
network resources. Changes in traffic patterns, securing mission critical business transac-
tions and the effects of infrastructure failures, low performance of Web protocols and reli-
ability issues over the Web create a need for Internet QoS standards. Often, unresolved
QoS issues cause critical transactional applications to suffer from unacceptable levels of per-
formance degradation. Traditionally, QoS is measured by the degree to which applications,
systems, networks, and all other elements of the IT infrastructure support availability of
services at a required level of performance under all access and load conditions. While tradi-
tional QoS metrics apply, the characteristics of Web services environments bring both
greater availability of applications and increased complexity in terms of accessing and man-
aging services and thus impose specific and intense demands on organisations, which QoS
must address.

Frequently asked questions

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Service-Oriented Computing ( SOC ) is a new computing paradigm that utilizes services as the basic constructs to support the development of rapid, low-cost and easy composition of distributed applications even in heterogeneous environments this paper.