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A MOBILE GEOGRAPHIC INFORMATION SYSTEM MANAGING

CONTEXT-AWARE INFORMATION BASED ON ONTOLOGIES

Anderson Resende Lamas, Jugurta Lisboa Filho,

Alcione de Paiva Oliveira, Ronoel Matos de Almeida Botelho Júnior Federal University of Viçosa – Departamento de Informática

Viçosa, MG, Brazil – CEP: 36570-000

{andersonlamas,jugurta}@ufv.br,{alcione, ronoeljr}@dpi.ufv.br

ABSTRACT

This paper presents the development of a Mobile Geographical Information System (Mobile GIS) capable of managing context information. This system was established from an architecture based on the specification of an ontology-based context model and a set of Web Services to access information remotely stored in a geographic database. This mechanism allows Mobile GIS users to receive personalized information in their mobile devices, combining the information on their profiles with the display of geo-spatial data. Keywords: Mobile geographic information systems, context-aware information.

1 INTRODUCTION

A number of fields of knowledge have been expanded through the use of technologies that exploit mobility and communication between users and devices. The steady expansion of the infrastructure wireless network and high proliferation of mobile de-vices, such as PDA `s (Personal Digital Assistant), Smartphones and mobile phones are some of the technologies that have favored this scenario.

In the field of Context-Aware Applications, for instance, one can use the dynamic context of mobile devices users, caused by the mobility and constant change in environment, and then to delivery personalized information. Context sensitive applications are characterized by use of context information to provide services and information relevant to users during a task execution [3]. In this scenario, context can be defined as any information that can be used to characterize a person, a place or object, relevant to an interaction between a user and an application [3].

As for the field of Geographic Information Systems (GIS), the intersection of geo-spatial data with mobile devices has led to the field of Mobile GIS. According to [8], Mobile GIS can be defined as a framework that integrates hardware and software to access spatial data (maps) through a wireless network, using mobile devices.

Considering their peculiar characteristics, both Mobile GIS applications and context-aware mobile applications bring with them major challenges to their development. A common challenge to these areas is to create a mechanism to bypass the limited capacity of mobile devices. Among these limitations are the little space to store data, low processing power, small screens and low bandwidth of wireless

device from storing a large amount of data locally or even processing them and give a timely reply.

For Mobile GIS, there is still the challenge of using proper technologies for storage, query and display of geo-spatial data on mobile devices. As example of these technologies we can mention geographic databases [19] and Geo Web Services [20].

For context-aware applications, one the of the challenges is how to define the most comprehensive and appropriate context model for the application domain being developed. Thanks to the power of representation and formal specification of ontologies, many studies have proposed this approach as a way of modeling context [14], [4] and [12].

The integration of context information in a Mobile GIS environment can add great value to the information that is displayed to an application user. This is due to the possibility of delivering personalized information to the user in combination with the display of geo-spatial data. In this scenario, this paper presents the characteristics and existing solutions for both the field of Mobile GIS and context sensitive applications and proposes an architecture for developing applications of Mobile GIS capable of managing context information.

Section 2 presents the architecture proposed for the development of context sensitive Mobile GIS. Section 3 presents a case study built to validate this architecture. Section 4 describes some related works. Finally, Section 5 presents the conclusions of this work.

2 THE CM-GIS ARCHITECTURE

(CONTEXT-MOBILE-GIS)

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integrated context sensitive mobile GIS applications. The development of Mobile GIS applications, as defined by Tomko [10], requires attention to: (a) storage and data query in a spatial database; (b) provide a mechanism for querying and accessing data remotely located; (c) the correct use of technology.

Regarding the geographic database (a) one must use a Database Management Sys-tem (DBMS) that is capable of storing and managing geo-spatial data. Some DBMS available today provide this functionality through an extension for spatial data, such as Oracle, SQLServer, PostGreSQL, among others. To deal with remote access to information (b), a frequently adopted solution is the use of Web Services, because of their ability to provide services that can be dynamically accessed by a network. Finally, with respect to the adopted technologies (c), it is important to choose a tool capable to manipulate and display geo-spatial data, both in its graphic and descriptive form in mobile devices.

In the case of context sensitive applications is important to establish a mechanism capable of representing and manipulating the context involved in the domain being treated by the application. Strang and Linnhoff-Popien [9] discuss that the key to the development of a context sensitive application is the definition of an appropriate context model, which can be defined by using ontologies.

The ontological characteristics of formality, explicit semantic and implementation abstraction enable software systems not only to infer new information from ontology-modeled information, but also to share the information among themselves so as to integrate, in a transparent way, the services that handle it [1].

Based on these characteristics, Bulcão Neto [1] proposed the Semantic Context Model (SeCoM), a domain-independent ontological model described in Web Ontology Language (OWL), which serves as basis for the definition of information in context. This model consists of a set of inter-related ontologies based on semantic dimensions of identity, location, time and activity.

SeCoM was developed using generic concepts in a way that it can be reused for a variety of context sensitive applications. To make this possible, the ontologies follow a two-layer approach: a top layer of ontologies, shown in Fig. 1, representing the model itself and the bottom layer of ontologies, which is built with concepts specific to the context-sensitive application that is being developed. In this layer, the SeCoM model can be reused or even extended with the knowledge specific to the application domain. Since the SeCoM model was generically defined, in this paper we suggest its use in the definition of the context model.

Figure 1: The SeCoM Model [1].

Based on the above-made considerations, we proposed the CM-GIS architecture for developing applications of context-sensitive Mobile GIS, as in Fig. 2. This architecture requires the following elements for the development of mobile GIS applications able to manage context information: 1. the mobile GIS application, which will be the

interface for the clients from their mobile devices. An important requirement for this application is to be able to manipulate and display geo-spatial data;

2. a set of Web Services to manage the communication and provision of services and information to the user. The use of Web Services has a great importance in this ar-chitecture, by allowing that operations demanding a high load of processing can be performed on more robust machines and not directly on the mobile device;

3. a module that communicates with Web Services and performs spatial queries, via SQL language, on information stored in geographic database; 4. a set of ontologies used to model the context

involved in the application. We suggest using the SeCoM model for modeling the context; 5. a defined module from the context model based

on ontologies that communicates with the Web Services to provide information in context. The information in con-text should also be stored in the database and queried via SQL;

6. a geographic database that manages all the geo-spatial data and descriptors in-volved in the application.

These items must be detailed according to the application that will be developed. The next section presents a case study, built upon this architecture.

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Figure 2: Context-Mobile-GIS Architecture (CM-GIS).

3 UFV-GEOMOBILE: A CASE STUDY This section describes the development of the UFV-GeoMobile system. This system was to target the campus of the Federal University of Viçosa (UFV), which is a public institution of higher education, with the main campus located in the city of Viçosa, Minas Gerais State. The university offers several under-graduate and graduate courses in numerous fields of knowledge. It receives annually a large number of people visiting or establishing some kind of relationship with its campus. Among these people, there are new students (~ 2000 per year), conference participants, visiting researchers, or simply people who want to visit their facilities. Moreover, there are also people who already have some connection with the University, such as professors, clerks or students. The common feature among these people is their often difficulty in identify-ing sites or services in campus, given its large area and the appearance of new buildings and facilities.

The university’s present scenario seems to be ideal for implementing a system to validate the CM-GIS architecture proposed in this work. The existence of a practical and automated information source available to the user seeking guidance in the cam-pus is a necessity. It would be even more appropriate that the options for querying and obtaining the information were customized according to the context in which the user is. For example, a visitor is probably not interested in the time of the next class, but on the directions of campus services (bank, pharmacy, etc.) or even the place of any event.

The UFV-GeoMobile was implemented, allowing a user of a Mobile GIS application on PDA to query or receive personalized information about the UFV Campus. This application is based on a map

of the campus properly managed by a component for geographic data handling. In addition, it has a set of query screens and a mecha-nism for information display based on the user context. More precisely, the context definition is based on a calendar of activities to be performed by the user and so to display the geographic location of the place where this activity will be performed.

The whole process of development is described in the following sections.

3.1 The context model: ontology of a university campus

The context model for the case study UFV-GeoMobile must contain information on the structure and activities carried out in a university campus. Information that must be modeled to reflect this domain includes:

• People: in this case students, staff and visitors. Employees may be teachers, researchers or technical and administrative staff;

• The administrative structure: it reflects the hierarchical organization of a university, including rectory, centers of education, departments and councils;

• The academic structure: involves activities related to teaching, research and extension;

• Calendar of activities: is the set of tasks that a person can perform on campus. This item is essential for the system to consider context information;

• Geo-spatial data: used to represent spatially the elements with geographic location on campus. Examples of these elements are buildings and services installed in each of these buildings. From this information it is initiated a formal representation of a context model. The context model of the UFV-GeoMobile system was based on the SeCoM model, proposed by Bulcão Neto [1], using the ontological concepts Actor, Activity, Spatial Event and Temporal Event.

A domain ontology defined as context model was termed OntoUFV and is represented in Figure 3. In this ontology, it was defined that people, derived from the ontology Actor of the SeCoM model, are divided into Visitor, Student and Staff, with the last item divided into Technician and Professor. These people are involved in activities inherited from the ontology Activity that occurs within a time interval (TimeInterval) and in a particular location (Physical Location).

The locations may be buildings or facilities, which are contained within the buildings. A location may be the campus itself, which has an Administrative Structure and an Academic Structure. The Administrative Structure consists of a set of Councils, which are divided into Technical Administrative Councils, Central Administration Councils and Representative and Adjoining Councils.

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The Central Administration Councils are divided into Rector, Pro-Rectors, Centers of Education and Departments. The Rector governs the Pro-Rectors and the Centers of Education. The Pro-Rectors govern the Technical Administrative Bodies and the Centers of Education govern the Departments.

The Academic Structure is divided into a number of Fields of Knowledge, which have different courses. Each course has a set of subjects which are offered by departments.

The context model has great importance to develop the application, as it was used as basis for the modeling of geographic database and the

implementation of features available in the context management module.

3.2 Building the geographic database

The geographic database of the UFV-GeoMobile system was built from the aggregation of a geospatial data set, kept by the university administration, associated with a set of relational databases used by a variety of administrative systems, also maintained by the institution. The geographic data have been modified to fit formats of data handled by the Mobile GIS application. Initially, data were stored in the format of the AutoCAD system and were converted:

Figure 3: OntoUFV: context model of a university campus. to Shapefile format, using the Cad2shape software [2]. The following layers were produced thoroughfare, buildings and specific facilities within a building, such as administrative offices and

laboratories.

The conceptual modeling of the database, as shown in Fig. 4, was determined from the information modeled in the domain ontology of a

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university campus. For this task, we used the UML-GeoFrame model [6], which is a specific model for geo-graphic database. Subsequently, the conceptual model was implemented using DBMS PostGreSQL with its spatial PostGIS extension.

The class diagram of Fig. 4 shows that the system has classes with and without spatial representation. According to the UML-GeoFrame model, classes and sub-classes Clerck, Professor, Admin Technician, Person, Student, Visitor, Calendar, Activity, Council and Type of Facility are specializations of non-geographic objects ( ), i.e., with no spatial representation. The classes Building, Thoroughfare and Facilities are perceived in object view ( ) and have spatial representation of the type

Area, Line and Point, respectively. Finally, the classes AerialView and ContourLine are perceived in the field view ( ). The first has spatial representation of the type GridCells ( ), whereas the second has representation of the type Isolines ( ).

3.3 Mobile GIS Application

The graphical interface of Mobile GIS was developed using the framework Microsoft Visual Studio 2005, C#.NET language and the Pocket PC 2003 emulator. SharpMap software was used to

Figure 4: Modeling of Geographic Database for UFV-GeoMobile.

display geo-spatial data, which is a set of controls based on the platform .NET to build GIS applications in mobile devices [7].

To allow access to information stored in the geographic database a Web Service was implemented in Java (SOAP), using NetBeans IDE 6.1 and the Glassfish server. For every feature available in the application of Mobile GIS, a corresponding operation in the Web Service was

developed to receive the parameters and pass them to the Spatial Queries Module or to the Context Management Module. To illustrate these operations, this work describes the option of locating a facility or service, location a person and the mechanism that shows the geographic location of an activity to be performed.

To locate a service or facility, initially the user enters the full or part of the name of the desired item,

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using the screen shown in Fig. 5-a. When typing the name and clicking on Search, the GetLocation operation is called, as described in Table 1.

This operation receives as parameters the typed name and the user’s coordinates (x,y) via GPS or via a mechanism implemented in Mobile GIS, which allows the users to indicate their location by inserting an icon on the map. This second choice was implemented so the user can use the UFV GeoMobile application, even with a PDA without an embedded GPS.

The operation GetLocation passes its parameters to the query module, generating a SQL query, also described in Table 1, which returns the names of sites that match the name entered, the distance of each facility in relation to the user's position and the coordinates of the building’s center point in which the facility is allocated. The selection carried out by the SQL query is returned to the mobile device that displays a list of available facilities (Fig. 5-a). By selecting one of the items in this list, the application indicates, through a small icon on the map, the location of the chosen facility, as shown in Fig. 5-b.

The operation to locate a person is similar to the process for identifying a service or facility. The location of a person is defined by the association of the individual with her or his work within the UFV. Initially the user enters the full or part of the person’s

name using the appropriate screen. Clicking the Search button generates the operation GetPerson of the Web Service, which is detailed in Table 2. This operation generates the parameters name and coordinates (x, y) of the user.

The operation GetPerson passes its parameters to the Spatial Query Module, generating an SQL query (Table 2), returning people’s names which correspond to the entered name, the respective UFV’s council to which the person is linked, the distance of each council in relation to the user's position and the coordinates of the center point of the building in which the council is allocated. The selection made by the SQL query is returned to the mobile device, which displays a list of possible people who meet the entered name. By selecting one of the items in this list, the application indicates, via a small icon, the location of the council to which the chosen person is linked.

The mechanism to notify the Mobile GIS users on the geographic location of any activity registered in their diaries was developed as a sensitive choice to the user’s context. Initially, to have access to this feature the user must be identified in the system using a login and password. From this moment, every minute the operation GetEvent is called, as in

(a) Facility query (b) Facillity location.

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Table 1: Web Service operation and SQL query to locate facilities .

@WebMethod(operationName = "GetLocation") public List<String> GetLocation(

@WebParam(name = "LocationName") String LocationName, @WebParam(name = "x") double x,

@WebParam(name = "y") double y) { ...

}

SELECT f.name, distance(b.the_geom,

GeomFromText('POINT(x, y)',-1)), Centroid(b.the_geom) FROM Building b, Facility f, FacilityType ft

WHERE (f.name like '%LocationName%') or

((ft.type= 'LocationName') and (ft.type = f.type)) and intersects(b.the_geom, f.the_geom);

Table 2: Web Service operation and SQL query to locate persons. @WebMethod(operationName = "GetPerson")

public List<String> getPerson(@WebParam(name = "PersonName") String PersonName, @WebParam(name = "x")

double x, @WebParam(name = "y") double y) {

... }

SELECT cl.nome, co.nome,

distance(b.the_geom, GeomFromText('POINT(x, y)',-1)), Centroid(b.the_geom)

FROM Clerk cl, Council co, Building b, Facility f WHERE (cl.nome like '%PersonName%') and

intersects(b.the_geom, f.the_geom) and (co.idCouncil = cl.idCouncil) and (co.idCouncil = f.idCouncil)

Table 3: Web Service operation and SQL query to notify events. @WebMethod(operationName = "GetEvent")

public List<String> GetEvent(@WebParam(name = "login") String login, @WebParam(name = "password")

String password, @WebParam(name = "actualTime") Object actualTime) {

.... }

SELECT a.description, a.iniTime, act.endTime, f.name, Centroid(b.the_geom)

FROM Building e, Facility f, Activity a, Calendar c, Person p

WHERE (a.horaIni – 'actualTime') = 10 and

(p.login = 'login') and (p.password = 'password') and intersects(b.the_geom, f.the_geom) and

(p.idperson = c.idperson) and (c.idCalendar = a.idCalendar);

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Figure 6: Screen to notify the user the occurrence of any activity.

Table 3. This operation receives as parameter, besides the login and password, the current time, which is obtained from the mobile device. This operation passes these parameters to the context management module which generates a SQL query (Table 3). This query returns all the user’s recorded activities to start in 10 minutes, describing the activity in detail, initiation and completion time, name of the facility in which the activity will be performed and the coordinates of the building’s center point where the facility is allocated. From this information, the Mobile GIS application displays a text box and indicates to the user the activity location through an icon, as in Fig. 6. 4 RELATED WORKS

The development of context sensitive mobile GIS applications has been studied by several groups. This section describes some of the works that contributed to accomplish the architecture proposed here.

Li et al. [5] provided a mechanism based on Web Services to display contextual information to mobile device users. Contextual information is defined through the user's location, via GPS, and information of used hardware and software. This context definition does not consider information on the user's profile or even addresses geo-spatial data.

Weibenberg [12] described the FLAME2008

platform, which was developed to be used in the Beijing Olympics. This platform is featured as a solution to deliver personalized information to mobile device users. This work uses a set of ontologies to define the user situation, trying to infer the activities that users could carry out over a period of time. Starting from the definition of the user’s position, the most appropriate information for that time is displayed via Web Services. Despite being a very wide system, this work does not describe the implications of integrating information in context into a Mobile GIS environment.

The CoMPASS architecture (Combining Mobile Personalized Applications with Spatial Services) [11] uses, in addition to information on profile and location, the user’s trajectory to automatically deliver personalized information to a GIS-Mobile client. The definition and storage of context information are based on the use of a set of log files. This approach differs from the solution proposed in this article, which suggests the use of ontologies to define context information and the use of a geographic database for storing data.

Brisaboa et al. [13] specifies a middleware to facilitate the queries on a geographic database from a mobile device. Access to information is made by Geo Web Services following the standards recommended by the OGC. This work provides a good reference on how to access and manage geo-spatial data from mobile devices, but does not take into account the context of the user to display the information.

Another very interesting work is the project MyCampus [14] in which a structure was developed based on Web Services and ontologies for the students of Carnegie Melon University (USA) to get on their PDAs a set of information based on their context within the campus. This work, although using some information on geo-spatial data, does not specify the challenges nor the necessary tools to build applications that handle such data.

NAMGIS [15] is a open-source context-aware Mobile Web GIS that exploits the knowledge of the user position to adapt the interface and track the user while he moves on the territory shown by the system on mobile device. It is composed of Core and a Framework (SAF). The Core provides an context-adaptable Web interface supporting principal GIS functionalities, such as map browsing, feature and attribute based queries. SAF supports the acquisition and elaboration of context data, including GPS data, used to track the user's position in real time and adapt the contrast/brilliance level of the interface in outdoor scenarios, and RFID (Radio Frequency Identification) data, used to detect the proximity.

Predic et al. [16] have developed a LBS and mobile GIS application framework named GinisMobile. It includes support for management

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and presentation of raster and vector spatial data, as well as dynamic data about mobile objects. The contextual data used in GinisMobile is encoded according to defined XML schema and transferred to the server for analysis and storage. On the client side, XML profile is parsed and used to customize user interface.

Considering the ideas and solutions presented in the works described above, we propose an architecture for developing applications for context-aware Mobile GIS, which is described in detail in the next chapter. The architecture proposed in this paper differs from other studies by proposing the reuse of a domain-independent context model, which is integrated to geo-spatial data management. This feature allows the development of a Mobile GIS capable of managing context information in several areas of application.

5 CONCLUSIONS

This work presented the specification of an architecture for the development of GIS-Mobile systems capable of managing context information. The characteristics inherent in this type of application was studied in order to reach the proposed solution, which includes: the use of Web Services to allow remote access to information from the mobile device, ontologies for context modeling and use of geographic database to store spatial data sets.

Using Web Services is an interesting solution to solve problems of lack of computational resources in mobile devices. This allows the implementation of more complex functionalities in more robust servers. Another advantage of using Web Services is the interoperability between different systems, which are described in different languages. An example is the application UFV-GeoMobile in which the system was implemented in C# and the Web Service in Java.

The use of ontologies to specify a context model has as the main advantage the possibility of specifying the correct meaning and relationship between the terms, avoiding ambiguous interpretations of the domain being modeled. Choosing the SeCoM model can facilitate modeling a great deal, because it addresses the various dimensions of contextual information and it was developed with the characteristic of domain independence.

A database diagram can be generated from an ontology by adding the information of the type of data and translating the formalism of the ontology-based knowledge representation into a database representation model as relational or object oriented model. Similarly, a database diagram can be used to establish the concepts to populate an ontology [17]. This approach to ontology-database mapping was used in the development of the application UFV-GeoMobile and was proven as a good way for

defining and obtaining context information. The use of ontologies in this work could be better exploited if there were a mechanism to handle the ontologies and infer new information before returning them to the Mobile GIS user. This will be addressed in a future work.

Another feature that can be further exploited is the use of Geo Web Services, which are services defined by the OGC (Open GIS Consortium) to address specifically geo-spatial data. This mechanism would avoid the need for installing an application on PDA, as it was done with the UFV-GeoMobile system. Instead, the Mobile GIS appli-cation could be accessed with a browser.

However, the architecture here presented, together with the UFV-GeoMobile developed as case study, show how the use of a Mobile GIS application capable of managing information in context can be very useful, especially the ability to provide personalized information combined with the display of geo-spatial data. Thus, this work presents a very practical and feasible way to develop applications for mobile GIS, presenting solutions to address typical challenges of applications involving geo-spatial data, context and mobile devices.

ACKNOWLEDGMENTS

This project was partially supported with funds from FAPEMIG - Foundation for the Support of Research of the State of Minas Gerais and CNPq / MCT / CT-Info.

6 REFERENCES

[1] Bulcão Neto, R. F. and Pimentel, M. G. C.: Toward a domain-independent semantic model for context-aware computing. In Proceedings of the 3rd Latin American Web Congress (LA-Web’05), pp. 61–70, Buenos Aires, Argentina. IEEE CS Press. (2005).

[2] Cad2Shp: Cad2Shp: AutoCAD DXF/DWG to ArcView Shapefile Converter. Available at: <http://www.brightergraphics.co.uk/guthrie/ cad2shp.htm>. Access: February 12, 2006 (2006).

[3] Dey, A. K.: Providing architectural support for building context-aware applications. Estados Unidos. PhD thesis (Doctor in Computer Science) - Georgia Institute of Technology (2000).

[4] Toivonen, S.; Kolari, J.; Laakko, T.: Facilitating mobile users with contextualized content. In: Procedings of Workshop Artificial Intelligence in Mobile System (AIMS 2003).

[5] Li, X.; Shin, W.; Li, L.; Yoo, S. B.: GIS Web Service Using Context Information in Mobile Environments. In: Proceedings of ICCSA 2006, LNCS 3980, pp. 895 – 903 (2006).

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[6] Lisboa Filho, J.; Iochpe, C.: Modeling with a UML profile. In: Shashi Shekhar and Hui Xiong. Encyclopedia of Geographical Information Science. New York: Springer. pp. 691-700 (2008).

[7] SharpMap: SharpMap: Geospatial Application Framework for the CLR (2008). Available at: <http://www.codeplex.com/SharpMap>. Access: August 17, 2008.

[8] Solyman, A. A.: Investigating Mobile GIS (2005). Available at: <http://www.direction smag.com/article.php/>. Access: May 28, 2007. [9] Strang, T.; Linnhoff-Popien, C.: A Context Modeling Survey. In: Proceedings of Workshop on Advanced Context Modelling, Reasoning and Management (UbiComp4). Nottingham-England (2004).

[10] Tomko, M.: Spatial Databases for Mobile GIS Applications. Eslováquia. Dissertação (Mestrado em Engenharia Civil) – Slovak University of Technology (2003).

[11] Weakliam, J., et al.: Delivering Personalized Context-Aware Spatial Information to Mobile Devices. In: Proceedings of W2GIS 2005, LNCS 3833, pp. 194–205 (2005).

[12] Weißenberg, N.; Gartman, R.; Voisard, A.: An Ontology-based Approach to Personalized Situation-aware Mobile Service Supply. GeoInformatica, v.10, n.1, pp. 55-90 (2006). [13] Brisaboa, N. R.; Luaces, M. R.; Parama, J. R.;

Viqueira, J. R.: Managing a Geographic Database from Mobile Devices Through OGC Web Services. In: Procedings of APWeb/WAIM 2007 Ws, LNCS 4537, pp. 174–179 (2007).

[14] Sadeh, N. M.; Chan, E.; Van L.: MyCampus: An agent-based environment for context-aware mobile services. In: Procedings of Workshop on Ubiquitous Agents on Embedded, Wearable and Mobile Devices (UBIAGENTS 2002). Bologna, Itália (2002).

[15] Brovelli, M.; Magni, D.; Brioschi, M.; Legnani, M.; Corcoglioniti, F.: NAMGIS - A Context-Aware Mobile Web GIS. FOSS4G 2008, North America. (2008).

[16] Predic B., D. Stojanovic and S. Djordjevic-Kajan,:.Developing Context Aware Support in Mobile GIS Framework.In: Proceedings 9th AGILE International Conference on Geographic Information Science, Visegrád, Hungrary, pp. 90-97 (2006).

[17] Viegas, R. F.: GeOntoQuery: um mecanismo de busca em banco de dados geográficos baseado em ontologias. Natal, RN, Brasil. Dissertation (Master in Computer Science) – Universidade Federal do Rio Grande do Norte (2006).

[18] Caduff, D.; Egenhofer, M. J.: Geo-Mobile Queries: Sketch Based Queries in Móbile Enviroments. In: Procedings of W2GIS 2005,

LNCS 3833, pp. 143-154 (2005).

[19] Castro, A.F.; Souto, M. V. S.; Amaro, V. E.; Vital H.: Desenvolvimento e Aplicação de um Banco de Dados Geográficos na Elaboração de Mapas da Morfodinâmica Costeira e Sensibilidade Ambiental ao Derramamento de Óleo em Áreas Costeiras Localizadas no Estado do Rio Grande do Norte. Revista Brasileira de Geociências. pp. 53-64 (2003). [20] Araújo, M.A.: Web Services na Informação

Geográfica. Braga, Portugal. Dissertation (Master in Informatic) – Universidade do Minho, Portugal (2005).

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