TOOLS FOR BUILDING CONTEX AWARE AND SECURE
PERVASIVE COMPUTING APPLICATIONS
Ran Zhao, Kirusnapillai Selvarajah and Neil Speirs
School of Computing Science, Newcastle University, Newcastle NE1 7RU, U.K.
Keywords: Smart Space, Middleware, Pervasive Computing, Wireless Networking, Context Ontologies, Modelling,
Testing, Dynamic Addressing, Communication Gateway, Eclipse.
Abstract: The increasing number of devices that are invisibly embedded into our surrounding environment as well as
the proliferation of wireless communication and sensing technologies are the basis for visions like ambient
intelligence, ubiquitous and pervasive computing. The PErvasive Computing in Embedded Systems
(PECES) project has developed the technological basis to enable the global cooperation of embedded
devices residing in different smart spaces in a context-dependent, secure and trustworthy manner. The
PECES project has also developed a set of tools which enable application developers to build and test
context aware and secure pervasive computing applications. This paper introduces the PECES middleware
that consists of flexible context ontology and a middleware that is capable of dynamically forming
execution environments that are secure and trustworthy. This paper presents a set of tools, namely Peces
Project Tool, Peces Device Definition Tool, Peces Ontology Instantiation Tool, Peces Security
Configuration Tool, Peces Event Editor Tool, Peces Event Diagram Tool and Peces Testing Tool which
enables developers to build and test pervasive computing application with the PECES middleware.
1 PECES PROJECT
The objective of the PECES project (PECES project,
2009) is the creation of a comprehensive software
layer to enable the seamless cooperation of
embedded devices across various smart spaces on a
global scale in a context-dependent, secure and
trustworthy manner. The increasing number of
devices that are invisibly embedded into our
surrounding environment as well as the proliferation
of wireless communication and sensing technologies
are the basis for visions such as ambient intelligence,
ubiquitous and pervasive computing. The benefits of
these visions and their undeniable impact on the
economy and society have led to a number of
research and development efforts. These include
various European projects such as EMMA (EMMA,
2006) that that develop specialized middleware
abstractions for different application areas such as
automotive and traffic control systems or home
automation. These efforts have enabled smart spaces
that integrate embedded devices in such a way that
they interact with a user as a coherent system.
However, they fall short of addressing the
cooperation of devices across different
environments. This results in isolated “islands of
integration” with clearly defined boundaries such as
the smart home or office. For many future
applications, the integration of embedded systems
from multiple smart spaces is a primary key to
providing a truly seamless user experience. Nomadic
users that move through different environments will
need to access information provided by systems
embedded in their surroundings as well as systems
embedded in other smart spaces.
Figure 1: Pervasive computing vision.
142
Zhao R., Selvarajah K. and Speirs N..
TOOLS FOR BUILDING CONTEX AWARE AND SECURE PERVASIVE COMPUTING APPLICATIONS.
DOI: 10.5220/0003823601420149
In Proceedings of the 2nd International Conference on Pervasive Embedded Computing and Communication Systems (PECCS-2012), pages 142-149
ISBN: 978-989-8565-00-6
Copyright
c
 2012 SCITEPRESS (Science and Technology Publications, Lda.)

PECES is committed to developing the
technological basis to enable the global cooperation
of embedded devices residing in different smart
spaces in a context-dependent, secure, and
trustworthy manner. The most innovative features of
the PECES middleware are to enable the
communication among heterogeneous devices across
the different smart spaces using dynamic addressing,
security and context ontologies.
Three different prototype applications have been
identified to evaluate the novel features provided by
the PECES project (PECES project, 2009). To
enable the application devlopment process, a set of
tools have been developed with the PECES project
consortium. This paper introduces the PECES
middleware and context ontologies and then focuses
on the development tools that have been developed
by the project consortium to enable PECES
middleware based application development and
testing. Section 2 introduces the ontologies
developed for the PECES project prototype
applications. Section 3 describes the PECES
middleware and its novel features such as role
specification, dynamic addressing, local and remote
gateway and security concepts. Section 4 describes
related work of development environment for
pervasive computing applications. The PECES
developments tools are discussed in Section 5.
Conclusions are then presented in Section 6.
2 CONTEXT ONTOLOGIES
Context ontologies define a common vocabulary to
share context information in a pervasive computing
domain and provide machine interpretable
definitions of basic concepts in the domain and
relations among them. They offer powerful
mechanisms for defining, acquiring, understanding,
processing and sharing context and inferring new
knowledge based on available data and context.
The PECES project has developed a general
purpose, domain independent middleware which
enables the seamless cooperation of embedded
devices across smart spaces on a global scale in a
context-dependent, secure and trustworthy manner.
From a data perspective this means that a possibly
very heterogeneous set of devices needs to
communicate information among themselves in
contexts and environments which cannot be
predetermined statically. Meaningful
communication, i.e., the understanding and correct
interpretation of the type, content and context of the
exchanged data is essential in this setting. While the
type and content of information is dependent on the
specific applications, the context in which the
application executes can be generalized and
described across application domains. Figure 2
shows an example of smart space ontologies
developed for the project. The PECES ontologies are
freely available from (PECES project, 2009) and
detailed information about the PECES ontologies
can be found in (PECES project, 2009).
Figure 2: Contextual concepts within a smart space.
The basic concepts to model the contextual
information of a smart space are Device, Context,
SmartSpace, Location and Service. The relationships
among them are shown in Figure 2. The Device
concept provides vocabularies to model specification
of devices inside smart spaces and the Context
concept is used to extend sub-concepts such as
LocationContext or SmartSpaceContext for
representing a set of context instances. The
SmartSpace concept is used to extend to different
kinds of smart spaces. Two main categories of smart
space are defined respectively by two subclasses
Non_StationarySmartSpace and
StationarySmartSpace. The StationarySmartSpace
concept represents smart spaces having fixed
location and the Non_StationarySmartSpace concept
represents mobile smart spaces. To express a smart
space provides a service, a Service instance is
referred by a SmartSpace instance using
service:provides property. The service:providedBy
property is used to express the fact that a service is
provided by a smart space.
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3 PECES MIDDLEWARE
The PECES project consortium built the targeted
cooperation layer on top of BASE middleware
(Becker, Schiele, Gubbels and Rothermel, 2003).
This enabled the project consortium to focus the
development efforts on the novel and innovative
features of the PECES middleware. The BASE
middleware is freely available as open source under
BSD license which facilitates the necessary
modifications and extensions and enables the free
reuse – even for commercial exploitation. The
BASE middleware enables the communication
between devices that are within communication
range.However, in order to achieve the goal of
providing cooperation layer that enables the
seamless interaction within and across the
boundaries of a single smart space, it was necessary
to extend the BASE concepts.
Figure 3: PECES middleware architecture.
The extension of the BASE middleware focused
communication gateway concepts, addressing
concepts and smart space and security concepts.
Figure 3 above shows the BASE components as well
as the new features added on top of that to achieve
PECES project goal. More detailed information
about the PECES middleware can be found in
(PECES project, 2009).
PECES middleware supports local gateways as
well as remote gateways. The main difference
between these two types of gateways is that the local
gateway locally shares the required knowledge. In
the remote case, the knowledge sharing should be
restricted to a minimum in order to avoid the costly
distribution of frequently changing information. The
remote gateways need to be realized differently in
that they require an external entity to distribute the
information that is distributed by means of device
discovery in the local case. This information will be
distributed by means of the Registry. More detail
information about the PECES Registry Interface can
be found in (PECES project, 2009).
3.1 Generic Role Assignment Concept
The extended PECES middleware provides
configuration and adaptation support by means of
generic role assignment. A role can be assigned to
any device as long as there are no further constraints
that limit the assignment. To enable the automated
computation of an assignment that reflects a
particular goal of a configuration task, generic role
assignment introduces rules. Rules define contextual
constraints on the assignment of roles to devices.
The simplest form of contextual constraint that is
generally useful for all configuration tasks is a
simple filter. An example of such a filter is to
demand that all devices should be at a certain
location. Another form of contextual constraint that
is particularly relevant for PECES are so-called
reference rules. Reference rules refer to a set of
devices that has been assigned a particular role. The
set of rules together with their corresponding roles
form a role specification. Given that the necessary
contextual information can be captured by sensors or
other types of information sources, one can use an
algorithm to automatically assign roles to the
devices whose context satisfies the constraints
specified by their rules. More detailed information
about role assignment concepts can be found in
(PECES project, 2009)
3.2 Smart Space Concept
A smart space can be defined as a group of
networked devices that cooperate to support their
users. The boundaries of a smart space are typically
defined on the basis of a geographic location, e.g. a
room or a building. However, such narrow
definitions are not flexible enough to support the
application prototypes in the PECES project.
Obviously, these smart spaces cannot be defined on
the basis of a single location. For example in
applications based upon a car, the whole car, i.e. the
smart space itself, is mobile.
In order to extend the definition, the addressing and
grouping scheme can be used to support the
formation of smart spaces based on arbitrary
contextual properties. However, the resulting
definition will be automatically restricted to devices
that are residing in the same local network. This is a
result of the fact that the formation process of basic
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groups is limited to a local network. Yet, for typical
smart spaces local connectivity is guaranteed.
To support smart space formation, the PECES
middleware introduces three additional components
which are coordinator, member and gateway. These
components can be easily motivated by looking at
the anatomy of the smart spaces that are identified in
the PECES Use-Case Specification (PECES project,
2009).
3.3 Security Concept
The PECES consortium extends the PECES
middleware to derive a secure middleware. For this,
PECES consortium introduced a basic trust model
that is used as basis for the concepts and
mechanisms of the middleware. These mechanisms
enable the secure interaction of devices. To enable
this, they span the management of cryptographic
keys, the authentication of information – specifically
context information and role assignments, the secure
data- and service-centric communication as well as
role-based access control. Although they do not
introduce additional interaction features, together
they span the whole set of security-related
requirements that have been identified in the PECES
Requirements Specification and thus, they are
sufficient to be applicable to a broad range of
scenarios.
The security mechanisms are modular and they
introduce a certain degree of configurability that can
be leveraged by application developers for
optimization purposes. This enables them to define
application-specific tradeoffs between security and
application performance. In order to simplify the
configuration of these mechanisms, the PECES
consortium provides set of tools (will be discussed
in this paper later) that simplify basic security
related tasks such as the distribution of keys and
certificates during application development.
4 RELATED WORK
A Middleware based application framework for
Active Space applications was proposed in (Roman
and Campbell, 2003). The Active Space consists of
the Gaia middleware OS (Roman and Campbell,
2000) managing a distributed system composed of
different kinds of system. The framework focuses on
providing an application framework that leverages
the functionality provided by the Gaia middleware
OS to assist developers in the construction of Active
Space application.
The Distributed Trust Toolkit (DTT) (Lagesse,
Kumar, Paluska and Wright, 2009) proposed a
framework for implementing and evaluating trust
mechanisms in pervasive computing systems and
introduced two new abstractions: trust groups and
trust blocks.
UbiWise, a simulator for ubiquitous computing
system was proposed in (Barton and
Vijayaraghavan, 2002). UbiWise concentrates on
computation and communication devices situated
within their physical environments. UbiREAL
simulator (Nishikawa, et al., 2006) was proposed for
realistic smart space systematic testing.
A suite of tools used to construct domain models
and knowledge-based applications with ontologies
was provided by Protégé (Protégé, 2004). Protégé
also provide a Java API for other developer to build
their own tools and applications.
The tools discussed above provide limited
support for application developers, as they have
been designed for different goals and concepts. They
only offer little methodological support for role
assignment, context-awareness and security, which
are the core features of the PECES middleware. The
PECES development tools aim to empower
application developers to make effective use of the
concepts and mechanisms provided by the PECES
middleware. The following section presents the set
of tools that have been developed by the PECES
project consortium to enable application developers
to build and test context aware and secure smart
space applications.
5 PECES DEVELOPMENT
TOOLS
The development tools suite provides features to
build and test applications based on the PECES
middleware. The tools are implemented as Eclipse
plugins. The development tools suite provides
number of tools to support different activities during
the application development and testing process. The
following sections explain the tool sets which are the
Peces Project Tool, the Peces Device Definition
Tool, the Peces Ontology Instantiation Tool, the
Peces Security Configuration Tool, the Peces Event
Editor Tool, the Peces Event Diagram Tool and the
Peces Testing Tool. The PECES Development Tools
are freely available online (with PECES middleware
library) and that can be installed in Eclipse IDE
using “Installed New Software” feature from the
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145

PECES project tools site: http://www.ict-
peces.eu/eclipsetools.
5.1 Peces Project Tool
This is the first step of the application development
process. Using this tool, a PECES general project
can be generated in the Eclipse workspace with three
different folders (ConfigurationTool, ModellingTool
and TestingTool) to keep different configuration,
modelling and testing related files which will be
generated by other tools in the development process.
The project generated by this tool is used to provide
interfaces with others tool via *.xml and *.owl files.
Figure 4: Screenshot of the peces project tool.
5.2 Peces Device Definition Tool
The Peces Device Definition Tool provides a
graphical user interface (GUI) for application
developers to specify the device description. This
tool can be used to define BASE/PECES
middleware communication plugins such as IP,
Bluetooth, ZigBee (e.g. MxIPBroadcastTransceiver,
MxIPMuticastTransceive, EmulationTransceiver),
and device functionalities (e.g. Coordinator,
Gateway, Coordinator&Gateway, Member) and also
device names. Developers can choose the
EmulationTransceiver plugin if they would like to
emulate their application. The devices can be
selected and placed in the Editor area of the tool and
necessary functionalities can be defined by right
clicking on the devices.
Figure 5 below shows an example application in
which four devices are defined (GUIDESYSTEM,
LOCATIONSYSTEM, VISITOR_IPAQ,
VISITOR_HTC). The GUIDESYSTEM is defined
as the coordinator of the smart space (shown in red)
and LOCATIONSYSTEM is defined as a gateway
device (shown in green). Two member devices are
VISITOR_IPAQ and VISITOR_HTC and those
devices are shown in blue in Figure below. The
figure also shows four different Java projects which
are automatically generated for each devices with
necessary PECES middleware library (peces-
2.0.jar).
Figure 5: Screenshot of the peces device definition tool.
5.3 Peces Ontology Instantiation Tool
This tool implements the features discussed in the
Configuration Tool section of D5.1 and provides a
user interface for static context properties. The Peces
Ontology Instantiation Tool enables the application
developer to instantiate the devices. This tool
supports all PECES ontologies as well as other
custom ontologies which application developers may
wish to use for their application. The Ontology
Instantiation Tool automatically loads the
participating device name and its assigned
functionality information from the project.xml file
which was generated by the Peces Device Definition
Tool. The Peces Ontology Instantiation Tool
provides GUI where application developers can add
instances and link context properties.
Figure 6: Screenshot of the peces ontology instantiation
tool.
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5.4 Peces Security Configuration Tool
The PECES middleware uses the OpenSSL library
to create necessary certificates and keys. As a result,
the Security Configuration Tool integrates the
OpenSSL toolkit to enable application developers to
generate keys and certificates for smart space
application. The Security Configuration Tool
provides an interface to gather necessary
information for root certificate, intermediate
certificate (trust chain) and client certificate. The
necessary information gathered from the Java
interface is passed to the OpenSSL command line
interface with the use of script files.
Figure 7: Screenshot of the peces security configuration
tool – root certificate creation.
Once necessary certificate chains are created,
they appear as trees in the Certificates section of the
tool. To generate a Client certificate, first,
developers must select the appropriate trust chain in
the tree, and then click on the “Client. Cert” button
to generate client certificate. The interface provides
feature to select the device for client certificate
configuration. When the process is completed, all
necessary root and intermediate certificates are
deployed in the “full” folder (full trust) in the
certificate folder and keys and client certificates are
also deployed in the certificate folder.
Up to this point, developers have configured Java
projects for devices with the PECES secure
middleware. The next step is to define the smart
space using the PECES Role Specification tool
which provides an interface where developers can
define the different rules that the application will use
to dynamically form groups of collaborative devices.
Actually, these rules are written essentially as
constrained queries over the context properties of the
devices. For that reason, the Peces Role
Specification Definition Tool loads the results of the
Peces Ontology Instantiation tool, showing, on a
tree-shaped diagram, all the devices that have been
defined in the project and their properties. The final
step of the application development process to use
the Peces Service Definition Tool to generate the
necessary service related Java code and Skeleton and
Proxy for any defined services in the Peces
Ontology Instantiation Tool.
5.5 Peces Event Editor & Diagram
Tools
The PECES Event Editor tool is used to define
single event definition. There are five different
events can be generated using the Peces Event
Editor Tool which are Delay Events, Device
SwitchON Event, Device SwitchOFF Event and
Context Event and Connection Event.
The Connection Event Editor consists of a full
featured graphical editor where application
developers can connect or disconnect any devices
already defined by the Peces Device Definition
Tool. Figure 8 shows a connection event which
generated for the example devices defined in the
Peces Device Definition Tool.
Figure 8: Screenshot of the peces event editor tool.
Figure 9: Screenshot of the peces event diagram tool.
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After generated all necessary events by the Peces
Event Editor Tool, application developers can now
use the Event Diagram Tool (Figure 9) to make
those events as a sequence. The Event Diagram Tool
enables application developer to model smart spaces,
dynamics connections and dynamic contexts for
testing. This tool generates test cases as a XML file
which is used by the Peces Testing Tool during the
testing. Figure 9 shows an Event Diagram Tool with
the events generated for this example application.
5.6 Peces Testing Tool
The Testing Tool enables application developers to
test the modelled application defined by the Peces
Event Editor Tool and Peces Event Diagram Tool.
For this purpose the Testing Tool generates another
new emulator Java project to centrally control other
device related events. In addition to the necessary
plugins, this new Java project should install the
EmulationTransceiver plugin. This emulator Java
project (run as new JVM process) is used to control
connections (add and remove connections) between
devices which is defined by the events.xml. This
project is also used to control the context changes
(add or remove) of any device. The Testing Tool
records all important middleware and application
related events in a common log file. The Peces
Testing provides three different editor pages:
Execute page, TestLog page and Visualise page.
Figure 10: PECES testing tool execute page.
The initial device status information is displayed
(for example, all devices are “OFF”) in the Testing
Tool Execute Page. Application developers are able
to define the required time to test the application
specified by the previous tools. Developers can also
provide Internet Registry IP and port information if
they want to test that application with the internet
registry. The Execute” button enables developers to
run the application. As seen in Figure 10, the status
of each device is shown during test (three devices
are “ON” and one device is “OFF” at a particular
time).
The TestLog page provides detailed information
of the test performed. Middleware and application
related events are logged with specific device name,
absolute time and other relevant and available
information.
Figure 11: Testing tool TestLog page.
The Testing Tool Visualisation Page provides
features to visualise the smart space network status
based on the test log data events with relative time.
The Page lists analyzed important events occurred
during the test. The “List of Events” may contain
event such Device Switch ON, Device Switch OFF,
Connection, Disconnection and Smart Space
Establish, Smart Space Join, etc. The status of the
system can be viewed by double clicking on the
name of the specific event. Double clicking on the
particular event from the “List of Events” provides
not only the particular event but also the status of the
whole network and its devices, its connections and
smart space activities, etc. at a particular time.
Figure 12: Screenshot of the Visualisation Page just after
devices joined the smart space.
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Figure 12 shows the visualisation of the system
at time 37089 ms (after test started). It displays the
four devices which at that time joined with the
“BoothNavigation” smart space define in this
example application. Figure 13 shows that the
LOCATIONSYSTEM left the smart space at 42170
ms (after the test started) due to its context property
changes (“LocationService” was successfully
removed).
Figure 13: Screenshot of the visualise page just after the
“locationservice” context was removed.
6 CONCLUSIONS
The main objectives of the PECES middleware are
to provide a cooperation layer that enables seamless
interaction and coordination among devices and a
development tools suite to build and test the
pervasive computing applications. This paper
presents a set of tools which provide support for
PECES middleware based application development
and testing. The tools provide support for device
configuration, ontology instantiation, security
configuration and role specification. The tools also
enable dynamic modelling of the network
connections and context changes. Finally, the tools
provide support to test the smart space application
performance and visualise the test results. It is the
authors’ intention to present complete set of tools
developed for the PECES project as a live demo at
the conference.
ACKNOWLEDGEMENTS
The work presented here is sponsored by EC under
FP7 programme (FP7-224342-ICT-2007-2) and
authors also would like to thank all the project
partners for their contributions.
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