A Survey on Context-aware Web Service
Systems
Hong-Linh Truong and Schahram Dustdar
Distributed Systems Group, Vienna University of Technology
{truong,dustdar}@infosys.tuwien.ac.at
Purpose of this paper
This survey aims at studying and analyzing current techniques and
methods for context-aware Web service systems, discussing future
trends and proposing further steps on making Web services systems
being context-aware.
Design/methodology/approach
We analyzed and compared existing context-aware Web service-
based systems based on techniques they support, such as context
information modeling, context sensing, distribution, security and
privacy, and adaptation techniques. Existing systems are also
examined in terms of application domains, system type, mobility
support, multi-organization support and level of Web services
implementation.
Findings
Supporting context-aware Web service-based systems is increasing.
It is hard to find a truly context-aware Web service-based system
that is interoperable and secure, and operates on multi-
organizational environments. Various issues, such as distributed
context management, context-aware service modeling and
engineering, context reasoning and quality of context, security and
privacy issues have not been well addressed.
Research
limitations/implications (if
applicable)
The number of systems analyzed is limited. Furthermore, the survey
is based on published papers. Therefore, up-to-date information and
development might not be taken into account.
What is original/value of paper
Existing surveys do not focus on context-awareness techniques for
Web services. This paper helps to understand the state of the art in
context-aware techniques for Web services that can be employed in
the future of services which is built around, amongst other, mobile
devices, Web services, and pervasive environments.
A previous version of this paper was published, as an invited paper, in the International
Journal of Web Information Systems, 5(1):5 - 31, (c) Emerald, 2009.
Last update: 4 August, 2009
A Survey on Context-aware Web Service
Systems
Hong-Linh Truong and Schahram Dustdar
Distributed Systems Group, Vienna University of Technology
{truong,dustdar}@infosys.tuwien.ac.at
Abstract
Being context-ware will improve how software adapts to dynamic changes influenced by various factors
during the operation of the software. Context-aware techniques have been widely applied in different
types of applications, but still are limited to small scale or single-organizational environments due to the
lack of well-agreed interfaces, protocols, and models for exchanging context data. Web services
technologies can support and simplify the exchange of context information in large scale, multi-
organizational environments, thus enable Web services systems to utilize various types of context
information to adapt their behaviors and operations to dynamic changes. Until now, an overview of
techniques and methods suitable for the development of context-aware Web services is missing. This
survey aims at studying and analyzing current techniques and methods for context-aware Web services
systems, discussing future trends and proposing further steps on making Web services systems being
context-aware.
Keywords: Web services, context awareness
1 Introduction
Web services technologies have advanced the development of Internet-based applications by facilitating
the integration and interoperability of services provided by different organizations. As a result, instead of
developing monolithic applications, today, we build large scale software applications by composing
loosely coupled services. By doing so, we can reuse and select suitable services as various organizations
can provide similar services for the development of different applications. However, when services are
loosely coupled to provide functions for a particular application, it is not easy to ensure that these services
are aware of each other and of the overall context associated with the application and its usage. This
awareness is, in particular, important because it improves the adaptation of services and applications to
situational changes during their operations.
What context information and context-aware system are, has been defined and discussed in various papers
(Dey, 2001) (Nihei, 2004) (Henricksen, et al., 2005) (Chen & Kotz, 2000) (Baldauf, Dustdar, &
Rosenberg, 2007). Context information is dependent on individual systems, as a type of information
might be considered as context information in one system but not in another one. Context-aware Web
services are a subtype of context-aware systems defined in these papers. In this paper, we consider context
information as any additional information that can be used to improve the behavior of a service in a
situation. Without such additional information, the service should be operable as normal but with context
information, it is arguable that the service can operate better or more appropriately. In this sense, a
context-aware service is considered as a smart Web service defined by Manes: "a web service that can
understand situational context and can share that context with other services" (Manes, 2001).
When applications are built from different services provided by and hosted in multiple organizations, it is
challenging to make the applications context-aware, as this requires services to be aware of each other
and aware of the context of customers and applications. This challenge is due to the distributed, large-
scale, diverse nature of Web service-based environments. Unlike past context aware systems of which
components are tightly coupled and in a closed environment, such as (Yan, et al., 2000) (Roman, et al.,
2002), as indicated by (Manes, 2001) (Nihei, 2004) (Truong, et al., 2008) and others, solutions for
enabling context sensitivity and sharing in Web services-based environments must be open and standard
based. These solutions cannot be proprietary and must be interoperable to ensure that they can be
applicable in Web service-based systems. Furthermore, as like other types of information in Web service-
based environments, context information can be sensitive and needs to comply with privacy and security
rules, when sensed and shared across the boundary of a single organization. This makes techniques and
methods for context-aware Web services very different from those of past context-aware systems. The
centralized models, based on proprietary or application-specific protocols and data representations, as can
be seen in the past context-aware systems, cannot be applicable in Web service-based environment.
Consider the trend of “the Future Internet”
1
which is built around, amongst other, mobile devices, Web
services, and pervasive environments, and consider the lack of well understanding on state of the art in
context-aware techniques for Web services, in this paper we aim at analyzing current techniques employed
in context-aware Web services. This paper presents a survey on Web services context awareness,
examines context sensitivity and sharing techniques, and discusses findings and recommendations for the
development of context-aware Web service systems.
The rest of this paper is organized as follows: Section 2 discusses the motivation for this survey and
related work, and outlines context-aware systems. Section 3 presents an overview of general context-
aware systems and context-aware Web service systems. Section 4 provides a detailed analysis of existing
techniques. We present our discussions in Section 5. A conclusion is given in Section 6.
2 Related Work and Motivation
Being context-aware allows software not only to be able to deal with changes in the environment the
software operates in, but also being able to improve the response to the use of the software. That means
context-awareness techniques aim at supporting both functional and non-functional software requirements.
It is, therefore, not surprising that there are already many surveys related to context-awareness in general.
However, existing surveys are not performed for context-aware systems in the Web services domain. This
is partly due to the fact that context-awareness computing has been focused on pervasive environments
(Abowd, Ebling, Gellersen, Hunt, & Lei, 2002), HCI (Human-Computer Interaction) (Moran & Dourish,
2001), and mobile computing (Chen, et al., 2000) (Solarski, et al., 2004) for a long time, while Web
services technologies have been relatively new. While many context-aware techniques could be useful for
Web service-based systems, it is not clear to which extent they are useful and how to apply them. Web
services technologies are designed for large-scale, loosely coupled environments that typically span multi-
organization boundaries. Such environments have very different requirements compared with closed or
1
http://www.future-internet.eu/. Last access: August 8, 2008.
single-organizational ones. Most existing context-aware techniques are designed for tightly-coupled
systems, within the control of a single organization. The interaction model between components in a Web
service-based system is also different from that of components in a single-organization environment.
Therefore, in order to understand how existing techniques can be used for Web services, it makes sense to
survey how context-awareness techniques are implemented in Web services and which ones can be
reused.
On the other hand, today, pervasive environments include various services built atop Web services
technologies. Mobile applications typically access Web services-based information systems. Web, mobile
and desktop applications are blended into pervasive, Internet-based environments that rely heavily on Web
services technologies. It is, therefore, useful to analyze the current practice and future trends in context-
aware Web service systems.
2.1 Context-aware Systems
There is a wide range of context-aware systems. Many systems have been studied in various papers. First,
we overview some generic context-aware systems, which are not based on Web services. We then
examine systems which are partially or completely based on Web services technologies.
2.1.1 Non Web Service-based System
Various context-aware systems have been developed. While they are not Web services-based, some of
them are distributed systems, and they have introduced and implemented various context-aware
techniques.
RCSM (Yau & Karim, 2004) is a middleware supporting context sensitive applications based on an object
model: context-sensitive applications are modeled as objects. RCSM supports situation awareness by
providing a special language for specifying situation awareness requirements. Based on these
requirements, application-specific object containers for runtime situation analysis will be generated.
RCSM runtime system obtains context data from different sources and provides the data to object
containers which conduct the situation analysis.
The JCAF (Java Context Awareness Framework) supports both the infrastructure and the programming
framework for developing context-aware applications in Java (Bardram, 2005). Contextual information is
handled by separate services to which clients can publish and from which they can retrieve contextual
information (Bardram, 2005). JCAF is based on the peer-to-peer model but it does not support automatic
discovery of peers or a super-peer. Also, the communication is based on Java RMI (Remote Method
Invocation). JCAF, however, supports various sensors for monitoring locations and base classes for
describing relevant entities used in context-aware applications.
The AWARENESS project
2
provides an infrastructure for developing context-aware and pro-active
applications. It targets applications in mobile networks for the healthcare domain. In AWARENESS,
applications will be context-aware and pro-active and are executed on top of a service infrastructure which
2
The AWARENESS project (AWARENESS: Context AWARE Mobile NEtwork and ServiceS),
http://www.freeband.nl/project.cfm?language=en&id=494. Last access: August 6, 2008.
provides generic components and manages context, security, and identity. The service infrastructure will
operate on a network infrastructure which supports context-aware mobility.
QoSDREAM (Naguib, et al., 2001) is a middleware based on a component model that supports the
development of context-aware multimedia applications. QoSDREAM gathers location-dependent
information from various sensors and delivers that information to applications through an event messaging
service.
The PACE middleware (Henricksen, et al., 2005) provides context and preference management together
with a programming toolkit and tools for assisting context-aware applications to store, access, and utilize
contextual information managed by the middleware. PACE supports context-aware applications to make
decisions based on user preferences.
The GAIA project is a CORBA-based middleware supporting active space applications (Roman, et al.,
2002). GAIA middleware provides a context service to support applications to retrieve as well as to
publish contextual information.
CAMUS is an infrastructure for context-aware network-based intelligent robots (Kim, Cho, & Oh, 2005).
It supports various types of context information, such as user, place and environment, and context
reasoning. However, this system is not based on Web services and it works in a close environment.
SOCAM is a middleware for building context-aware services (Gua, Punga, & Zhang, 2008). It supports
context modeling and reasoning based on OWL. However, its implementation is based on RMI.
Note that many context-aware systems in this category are network-based. Some rely on RMI and
CORBA technologies. However, they do not rely on Web service technologies and are not designed to
work on Web service-based environments. In addition, most of them have been surveyed in other papers
(see Section 2.2). Therefore, we do not survey them in this paper, but refer to their techniques in case
similar techniques are used in context-aware Web service systems.
2.1.2 Web Service-based Context-aware Systems
This section aims at providing an overview of context-aware systems built around Web services
technologies. Not all parts of a Web service-based context-aware system might entirely be based on Web
services. In this case, we will highlight only the context-aware Web service related parts.
The Akogrimo project
3
aims at supporting mobile users to access data, knowledge, and computational
services on the Grid. With respect to context awareness, Akogrimo concentrates on context that is related
to situations of mobile users, such as user presence and location, and environmental information (Osland,
et al., 2006). The core context-related components in Akogrimo are a context manager which collects
contextual information and delivers it to applications.
3
The Akogrimo project (Akogrimo: Access to Knowledge through the Grid in a mobile World)
http://www.mobilegrids.org/. Last access: August 5, 2008.
