Integrating local services and applications into

external user home environments

Helder Pinto and Rui Jos´e

University of Minho, Information Systems Department

Campus de Azur´em, 4800-058 Guimar˜aes, Portugal

Abstract. Users moving between diﬀerent ubiquitous computing envi-

ronments should be able to take a full proﬁt of the resources existent

there, if their home environment (e.g. a mobile portal) could seamlessly

integrate with local infrastructure. Pursuing such goal, this paper fo-

cuses on the aspects of integrating local applications and services into

an external user home environment, with particular emphasis on the

interoperability and performance issues. Based on the concept of Value

ADded Environment (VADE), as an administrative and physical domain,

where the locally available facilities can be combined with external user

home environments, the paper presents a middleware solution support-

ing the integration of local services and applications available in VADE

environments into an external portal.

1 Introduction

Research in ubiquitous computing has resulted in prototype ubiquitous comput-

ing environments that are often characterized by a strong integration between

the computational infrastructure and the physical environment. The main ad-

vantage of this strong coupling with the physical environment is essentially the

possibility to support functionality that is very speciﬁc to that particular en-

vironment. The main limitation, however, is that such level of integration can

only be reasonably achievable for systems aimed at small and speciﬁc physical

infrastructures, meaning that, in the course of a day, a user will have to interact

with a multitude of independent ubiquitous environments, one for each visited

location. This limitation is even more important due to the lack of an adminis-

trative infrastructure that could be used across domains to support key features,

such as authentication, user proﬁling or billing.

Mobile network operators (MNO) are also launching services, usually by

means of a mobile portal, that use the position of mobile terminals to provide

users with information that is associated with their particular location. These

location-based services are available everywhere and have a strong administra-

tive framework, but they require from the server to provide information for any

of the potential locations of the client, which implies the ability to consolidate all

location-based contents into large warehouses, posing operational and data in-

tegrity issues that are costly to overcome [1]. Furthermore, these applications are

Pinto H. and JoSÉ R. (2004).

Integrating local services and applications into external user home environments.

In Proceedings of the 1st International Workshop on Ubiquitous Computing, pages 119-128

DOI: 10.5220/0002679601190128

 SciTePress

not able to explore resources that may be available in the physical environment.

Without the assistance of a local infrastructure, these applications do not have

the potential for reaching the same level of richness and context-awareness as the

ubiquitous computing applications created for a speciﬁc physical infrastructure.

This research aims to combine the two previous approaches, and is speciﬁ-

cally targeted at the issues of interoperability and seamless integration between

a user home environment (e.g. a MNO portal) and the ubiquitous computing

environments corresponding to the physical locations visited by the user. Our

approach introduces the concept of Value ADded Environment (VADE) as an

administrative and physical domain, e.g. a shopping center or an airport, where

the locally available ubiquitous computing facilities can be combined with the

external home environment of visiting users. The overall scenario is that when

entering a VADE, mobile users are provided with functionality that corresponds

to the dynamic combination of predeﬁned user preferences, currently active ap-

plications, current user context and locally available services and applications.

While this research copes with multiple challenges, this paper focuses only on

the integration of lo cal resources into an external environment. The paper de-

scribes the main issues implied in the integration between local and external

environments, namely interoperability and performance, using the VADE sys-

tem as a representative example of the integration challenges. The paper argues

for the need for an integration middleware dealing with the identiﬁed issues, and

describes the solution we developed for the VADE system. For a more complete

description of the VADE system and other aspects covered by this research,

please refer to [2].

The next section describes the VADE concept, its application models, and

the system architecture. Section 3 introduces the issues of dynamically integrat-

ing local applications and services into the user home environment. Section 4

explains how we dealt with those integration issues by the use of a VADE-aware

integration middleware.

2 Value Added Environment

The VADE concept is here presented as an example of integration between local

and external environments. The idea behind this concept is that when a user

enters a ubiquitous computing environment that also happens to be a VADE sys-

tem, the functionality available to that user should be the combination of global

and local functionality. In order to clarify these relationships, we have grouped

the overall system functionality into three separate domains, more speciﬁcally:

User, VADE, and External domains. The User domain corresponds to the physi-

cal and logical elements carried by a p er son that is within the physical b oundaries

of a VADE. The VADE domain corresponds to elements constituting the local

infrastructure and directly supporting the VADE functionality (e.g., services,

applications, and all sorts of devices – sensors, input/output, etc.). Finally, the

External domain corresponds to all the other elements that interact with the

VADE but are not part of the VADE, or user domains. Our main assump-

120

tion about the External domain is the existence of a structured framework for

customer relationship that is able to support key horizontal services, such as

personal context management, user proﬁles, and a personal information space,

possibly in the form of a mobile portal.

2.1 Application models

VADE-aware global applications. A VADE-aware global application is an

external application that, when the user enters a VADE, is able to enhance

its functionality by taking advantage of the locally available services. A global

application is not aimed at any VADE in particular and may be used regularly

outside a VADE. We assume that these applications are context-aware, and also

that, as users move, they are continuously searching for additional location-

based resources. Entering a VADE is thus a major opportunity for ﬁnding new,

probably much more speciﬁc, resources and context information that will allow

them to improve their relationship with the physical environment of the user,

and thus the value of the provided functionality. For example, it is simple for a

global map application to present a detailed map of the area where a shopping

center is located, but for the people inside the shopping what would be real value

would be to have access to a detailed plan of the shopping. The main challenge

is to be able to discover, recognize and use the potentially very vast range of

services that may be found at diﬀerent environments.

VADE Local Applications. A VADE local application provides function-

ality that is s peciﬁcally associated with a particular VADE. When a user enters

a VADE, these applications should seamlessly integrate with the users mobile

information space. i.e. the user should not need to look for them, conﬁgure them

or study their functionality. The main advantage of this application model over

the VADE-aware model is that, since these are local applications, they can be

tailored for the particular environment for which they were pr oduced. The main

challenge for this type of application is how to manage their integration into the

user external environment.

2.2 System architecture

Figure 1 depicts the VADE system architecture. The main components of the

VADE architecture are a browser (User domain), a personal portal and a per-

sonal context manager (External domain), and a s et of applications and services

in the Vade domain (some of which are not stated in this paper for the sake of

conciseness).

Each mobile user has her/his own Context Manager, which gathers and ag-

gregates context information (e.g. location, activity, etc.) from several context

sources. The Personal Portal relies on the Context Manager to obtain user con-

text information, possibly inﬂuencing the content produced by each portal appli-

cation (also called portlet). The context information may contain a notiﬁcation

of the user entrance in some VADE domain. This notiﬁcation contains a refer-

ence to the VADE’s internet domain name, which is a basis to access the VADE

121

VADE domain

UDDI Registry

<<web service>>

Location-based

Services

<<web service>>

Local Applications

Providers

<<WSRP producer>>

VADE Entry Point

<<WSIL document>>

User Device External domain

Personal PortalBROWSER Context Manager

Fig. 1. General architecture of the VADE system

Entry Point at a well-known URL. The VADE Entry Point is a Web Services

Inspection Language (WSIL) [3] document providing references for the VADE

core services. One of the VADE core services is a UDDI registry that is used

by the Personal Portal and its VADE-aware global applications to discover local

resources (applications and services respectively). VADE Local applications cor-

respond to Web Services for R emote Portlets (WSRP) [4], a standard allowing

for the integration of remote portlets into a portal. Location-based Services are

also Web Services that implement a well-known interface used by VADE-aware

global applications.

3 Integrating local resources into external environments

This section describes the main problems of integrating local ubiquitous infras-

tructures with external environments: interoperability and performance. These

issues are analyzed in the scenario considered in our work, where essentially two

forms of integration between local and external environments take place: VADE

location-based services are used by VADE-aware global applications running on

external portals; and VADE local applications are integrated into external per-

sonal portals. We believe the issues raised by this scenario represent the general

cases of integration between local and external environments, and thus our work

should be viewed as a model of how to deal with these speciﬁc issues.

3.1 Interoperability

Interoperability is an unavoidable challenge for the integration between hetero-

geneous environments. However, external user home environments should not be

faced with several diﬀerent integration mechanisms for each local environment

the user moves in. A homogeneous ground for local resource discovery and ac-

cess should exist between all local environments, so that interoperability with

external environments is possible.

122

For example, VADE-aware global applications are continuously searching for

local resources in order to provide ﬁner-grained information to mobile users.

The need for interoperability essentially comes from service discovery and ac-

cess. VADE-aware global applications must rely on widely accepted protocols

for service discovery and access. Furthermore, local services interfaces should

be well-known, so that VADE-aware global applications developers can assume

some level of homogeneity in the diﬀerent services their applications interact

with.

The discovery of local VADE applications requires the same homogeneity

than service discovery. Moreover, local VADE applications must b e clearly dis-

tinguished from other types of applications, requiring conformance to a given

application format. Integrating local VADE applications functionality and user-

interface into an external environment also requires agreed protocols.

3.2 Performance

Integrating external environments with local resources implies multiple, often

time-consuming interactions (e.g. discovering and interacting with local resources).

Continuous changes in the user context originate correspondent interactions with

the local environment in order to keep contents up to date with the context.

Fur thermore, the external home environment may be physically distant from

the local infrastructure, which implies a cost on the time required for the inter-

actions. Using physically near resources (from the user’s viewpoint) should not

result in visibly worse performance, otherwise users may think out of a proximity

paradox.

VADE-aware global applications are particularly aﬀected by the performance

issue. Since the moment a user enters a VADE domain, several time-consuming

steps are undertaken until the information is presented by each application to a

portal user: a) obtaining the user context from the Context Manager; b) access-

ing the VADE Entry Point to obtain the URL of the local registry; c) querying

the local registry for a service type available at the user location; d) interacting

with the service to extract relevant information; and e) integrating it into the

information to be presented to the user. Furthermore, the last two steps are re-

peated every time the user physical location inside the VADE domain changes. If

we consider that dozens of VADE-aware global applications may be constantly

performing those operations, multiplied by hundreds of us ers moving inside a

VADE domain, performance becomes a ﬁrst-class issue. Therefore, some mech-

anism must be implemented to alleviate VADE-aware global applications from

all that burden.

The integration of local VADE applications into an external environment is

also time-consuming. When a user enters a VADE domain, local applications are

discovered and integrated into the running external environment. These opera-

tions should not have an impact on the user experience, i.e., they should occur

as invisibly as possible, so that the user does not have to hang on waiting for

the integration operations to conclude in order to proceed with the experience.

123

Likewise, when leaving the VADE domain, the removal of local applications from

the external environment should not annoy the user.

3.3 Solving the integration issues

Fr om this analysis, we conclude that a solution for the integration between local

and external environments must guarantee interoperability and an acceptable

level of performance at all levels of the integration. The solution we propose

to deal with interoperability issues is based on widely accepted standards: all

components of diﬀerent domains interact with each other over HTTP and SOAP;

local applications and services are discovered using UDDI; ﬁnally, local VADE

applications are implemented as WSRP portlets, a standard allowing for remote

access to user-facing p ortal components.

Our solution for managing the performance issue consists of an integration

middleware coupled to the external user home environment. Such a middleware

intermediates the interaction with the local environment, acting on behalf of

the external environment components, and thus saving a considerable number

of time-consuming operations. In the next section, we describe the integration

middleware solution we developed in the context of the VADE system.

4 Personal VADE-aware Middleware

The Personal Vade-Aware Middleware (PerVAM) is a component of the exter-

nal environment whose main functionality is to mediate interactions with the

VADE system. The PerVAM middleware provides mechanisms improving the

performance of local applications and services integration into external portals.

The PerVAM functionality is to: 1) manage the integration of local applications

into the portal every time the VADE domain entrance/exit is detected; 2) act

on behalf of VADE-aware global applications in the process of discovering and

interacting with VADE core and location-based services, each time the user lo-

cation changes; and 3) intermediate interaction between global applications and

Context Manager.

The PerVAM middleware is especially useful for dealing with the time-

consuming operations performed by VADE-aware global applications (see Sect.

3.2) each time a local service is needed. Redundant operations, like VADE core

services discovery, are performed by PerVAM only once, just after a user enters

the VADE domain. This relieves applications from repeating unnecessarily the

same operation. Other operations are only needed when the Context Manager

notiﬁes context change. Obtaining user context, discovering local services, or in-

teracting with local services are examples of such operations. Without PerVAM,

most of these operations would be performed by VADE-aware global applica-

tions, each time the user loads the portal page in her/his browser, even if the

context had not changed. This results in signiﬁcant and unnecessary overhead,

specially if a portal page is composed of multiple VADE-aware global applica-

tions. The PerVAM middleware relieves applications from those time-consuming

124

operations, by pre-fetching, in the background, context and application-speciﬁc

information, each time the Context Manager notiﬁes a user context change (when

in the VADE domain). This information is further directly accessed (at the user

proﬁle) by applications only when they are invoked by the user, drastically im-

proving their performance.

4.1 Architecture and functionality

The PerVAM architecture (see Fig. 2) is composed by the PerVAM servlet, the

portal database, the VADE-aware global applications surrogates, and the Per-

VAM API. The PerVAM servlet is responsible for managing user context changes

and its inﬂuence on the integration of local resources. The portal database stores

the proﬁle for each registered user, containing portal- and VADE-related in-

formation. Each VADE-aware global application surrogate pre-fetches, in the

background, location-based information for the application it represents. Finally,

the PerVAM API provides a higher-level interface for both the p ortal and the

VADE-aware global applications to use PerVAM functionality, such as access

to application-speciﬁc content, access to user context, local service discovery, or

mediation of interactions with WSRP producers.

PerVAM

servlet

Portal

database

VADE-aware

global

applications

surrogates

PerVAM

API

Fig. 2. PerVA M architecture

When the PerVAM servlet is initialized (or whenever a new user registers

to the portal), it subscribes portal users for context update notiﬁcations in its

respective Context Manager. When the Context Manager sends a notiﬁcation to

the PerVAM servlet, PerVAM asks the Context Manager for the corresponding

user’s context and checks if the user has entered/left a VADE domain, or if the

location of a user that previously entered the VADE has changed.

If the user has entered a VADE, PerVAM performs all the neces sary integra-

tion steps (see Fig. 3). This happens only once for each VADE the users moves

in. It starts by discovering VADE core services through the VADE Entry Point.

Among other core service URLs, the URL of the local UDDI registry is stored in

the user proﬁle for further reuse. PerVAM then searches for local applications,

by querying the UDDI registry for WSRP producers. The local WSRP producer

is then queried to obtain the references to the portlets it oﬀers. PerVAM ﬁ-

nally integrates each WSRP portlet reference in the user’s portal. If the user has

left a VADE domain, PerVAM simply erases references to previously integrated

WSRP portlets.

125

Context

Manager

VADE Entry

Point

User

profile

WSRP

Producer

PerVAM

getContext()

context info

store core services URLs

void

update notification

get core services URLs

core services URLs

registration handle

getPortletsDescription

portlets description

UDDI

registry

findService(“WSRP Producer”)

local WSRP Producer info

Fig. 3. Sequence diagram for the integration of local VADE applications

Each time the user location is updated

, PerVAM notiﬁes every VADE-aware

global application surrogate (see Fig. 4). Each s urr ogate then queries the UDDI

registry for needed services associated to the new user location. The surrogates

then interact with those services and store the collected information in the user

proﬁle. Finally, each time a user portal page is displayed, VADE-aware global

applications ask PerVAM to extract from the user proﬁle the latest information

their respective surrogates collected from location-based services.

VADE-aware global

apps surrogates

UDDI

registry

Local

services

PerVAM

findService(...)

service info

collect information

context update

notification

location-based information

User

profile

store collected information

void

Fig. 4. Sequence diagram for the location-based information pre-fetching

entrance in a VADE domain is regarded as a location update

126

Global VADE-aware applications implement location-based information pre-

sentation, while their surrogates gather the required information from each

VADE. Each sur rogate’s functionality depends on the application it represents,

both parties agreeing on some protocol to represent the collected information.

Surrogates do not implement any other location-based functionality than those

related to VADE environments. Information whose scope is outside a VADE is

gathered by applications themselves.

4.2 Prototype

The prototype we have been developing is composed of a VADE system serving

the university campus, two external portals, and a number of mobile devices

(laptops, PDAs, and mobile phones). The VADE system oﬀers a set of local

services and applications, and diﬀerent types of contextualization mechanisms.

The external portals include some VADE-aware global applications supported

by their own PerVAM middleware.

Portal development was based on the Jetspeed op en-source platform [5]. For

location-based services we used Axis [6], and for WSRP portlets development

and production we used WSRP4J [7].

5 Related work

The MIDAS project [8] explores the proactive, dynamic functional extension of

mobile devices, by means of a local infrastructure, and using the aspect-oriented

programming paradigm. The supporting scenario proposes that when mobile

devices enter a new computing environment, the environment provides the nec-

essary extensions so that the device can operate in that location at that moment.

The scenario assumes that mobile devices must carry a platform that is able to

dynamically acquire, apply, and discard extensions as needed. While MIDAS sets

the initiative of extending functionality to the local infrastructure, our approach

confers the active behavior to the external environment. Besides that, MIDAS

only allows for extending a speciﬁc functionality with local characteristics. Our

approach goes beyond that, making possible to add new, diﬀerent functionality,

augmenting the functional scope of the external environment.

The second perspective relating our work to others is the pre-fetching mech-

anism. Pre-fetching has been proposed as a valuable strategy to increase perfor-

mance in Web usage. The performance increase can be accomplished by pr e-

fetching hyperlinks [9]. This technique corresponds to pre-fetching web doc-

uments referred by hyperlinks in another web document. The decision about

which documents to pre-fetch derives mainly from the evaluated access prob-

ability of each hyperlinked document. The approach we implemented in the

PerVAM middleware for augmenting the performance of VADE-aware global ap-

plications is very similar to pre-fetching in the WWW. However, location-based

information access probability is not considered in PerVAM. As future work, we

could consider this topic and also take into account the relevance of updating

127

location-based information in speciﬁc situations. For example, a VADE-aware

global application providing map information should not require from its surro-

gate to search for a local map service each time the user location changes, as the

user may be moving in a region that may be well represented by a single map.

6 Conclusions

This paper has described part of an ongoing work in which the concept of a

value-added environment (VADE) is explored as a mechanism for enabling the

combination of functionality between a local ubiquitous computing infrastruc-

ture and external user home environments. We focused on the integration of local

services and applications into external environments, with particular emphasis

on the interoperability and performance issues. The paper presents the PerVAM

middleware, a solution to support the integration of local VADE applications

and services into an external portal. Based on Web Services standards, and thus

promoting interoperability, PerVAM also improves integration performance, by

means of a lo cation-based pre-fetching mechanism.

7 Acknowledgements

This work was carried out as part of the VADE project supported by the Por-

tuguese Foundation for Science and Technology (Ref. POSI/CHS/38475/2001).

References

1. OGC: In support of an open location services (OpenLS) testbed. Technical report,

Open GIS Consortium (2000)

2. Jos´e, R., Pinto, H., Meneses, F., Boas, N.V., Rodrigues, H., Moreira, A.: System

supp or t for integrated ubiquitous computing environments. In: System Support

for Ubiquitous Computing Workshop (UbiSys) at the 5th Annual Conference on

Ubiquitous Computing (UbiComp 2003), Seattle, United States (2003)

3. I BM: Web services inspection language (2001) http://www-

106.ibm.com/developerworks/webservices/library/ws-wsilspec.html.

4. OASIS: Web services for remote portlets (2003) http://www.oasis-

op en.org/committees/wsrp.

5. A pache: Jakarta Jetspeed (2003) http://jakar ta.apache.org/jetspeed.

6. A pache: Webservices Axis (2003) http://ws.apache.org/axis.

7. A pache: Webservices WSRP4J (2003) http://ws.apache.org/wsrp4j.

8. Pop ovici, A., Frei, A., Alonso, G.: A proactive middleware platform for mobile com-

puting. In: 4th ACM/IFIP/USENIX International Middleware Conference (Mid-

dleware 2003), Rio de Janeiro, Brazil (2003)

9. Duchamp, D.: Prefetching hyperlinks. In: 2nd Usenix Symposium on Internet

Technologies and Systems, Berkeley, United States (1999)

128