ON GEOSPATIAL AGENTS

Merik Meriste, Tõnis Kelder, Jüri Helekivi, Andres Marandi

Tartu University Institute of Technology , 51014 Tartu, Estonia

Leo Motus

Tallinn Technical University, 19086 Tallinn, Estonia

Keywords: geospatial technology, geospatial agent, multi-agent system, agent-based computing

Abstract: As access to spatial and real-time data improves, the need for appropriate software tools has become

prevalent. To develop geospatial applications in this context requires an approach to software architecture

that helps developers evolve their solutions in flexible ways. Two concepts are today considered reasonable

here – web services and agents. This paper presents generic geospatial agents in a prototype of agent

development environment KRATT. Pilot applications are described and experience discussed.

1 INTRODUCTION

As access to spatial and real-time data improves, the

need for appropriate software tools has become more

and more prevalent. To meet the demands of such

systems one needs tools for developing systems of

autonomous, interactive software entities. The Open

Geospatial Consortium (McKee 2003a, 2003b)

tackles the challenge of developing tools to support

the integration of spatial capabilities into

applications than don’t depend on a full-featured

Geographic Information Systems (GIS). The main

problem is - embedding of location-aware and time-

aware components into geospatial applications.

The current practice of agent-based systems

(Bigus, 2002) is mostly focused on agents’

intelligence related issues. The problem of multi-

agents’ organisation and engineering has received

less attention (Odell et alii, 2003). In principle, an

active object with full control over its state forms a

pragmatic basis for agent’s implementation. Two

concepts are today considered reasonable to how to

address this – web services and agents. This paper

presents implementation of generic geospatial agents

in an agent development environment KRATT

(Motus, 2004). Basics of KRATT agents as well as

conceptual line of development are described in

section 2. Basic collection of geospatial agents is

introduced in section 3. Pilot applications are

superficially considered in section 4.

2 AGENT’S STRUCTURE

Agents exist and interact in a computer system that

is distributed across a set of, not necessarily

homogeneous, networks. The agents can exist

completely in a virtual world – interacting only with

the other agents, or also interacting with non-agent

components of the system. The prototype

development is carried out in C# and .NET since this

platform is suitable for controlling multiple threads

needed in agents. An application as an agent system

consists of administrative agents, and application

agents. All the agents are generated from pre-

specified classes. Classes form the namespace

AgentComponents written in C#.

An agent is implemented as (see Figure 1) an

instance of a class Agent in the namespace

AgentComponents. This base class determines

functionalities and lists related components that are

to be applied to generate an instance of a location-

and time-aware agent. As a rule, a multi-agent

system comprises several agents; each agent is

implemented as Windows application (WinA).

Basic components of class Agent are:

(1) Communicator, exchanging (time-stamped)

messages with the other agents;

(2) Manager, managing control of agent’s ;

(3) Actor, performing the functional tasks;

(4) Monitor, monitoring specified aspects and time-

stamped events in the agent’s behaviour.

210

Meriste M., Kelder T., Helekivi J., Marandi A. and Motus L. (2005).

ON GEOSPATIAL AGENTS.

In Proceedings of the First International Conference on Web Information Systems and Technologies, pages 210-213

DOI: 10.5220/0001230402100213

 SciTePress

Each component is described by a class in the

namespace AgentComponents. In the most cases the

Communicator is standardised, whereas the other

components are different in different applications.

Majority of agents, i.e. application agents carry

out their autonomous (maybe) proactive tasks. When

specialising an application agents it is necessary to

specialise its components Communicator, Manager,

Actor, and Monitor. In the same WinA are

constructed all components of the agent.

Administrative agents are specific in a sense that

they store and execute the rules, and provide

common services, required for expected normal

operation of application agents: Basic types of

administrative agents are:

(1) AMS Agent - management of application agents.

(2) Proxy Agents - transferring messages to and

from agents that reside behind a firewall.

(3) Monitor Agent - collecting and processing

activity reports of application agents.

Proxy and Monitor agents have also to register

themselves with the corresponding agents AMS type.

3 GEOSPATIAL AGENTS

Agent based digital map enables a customer to use in

his/her computer a variety of digital map based

applications. The customer’s computer must have a

web browser, and sufficient memory space for

automatically downloaded active map object

together with some other active objects, necessary to

solve the particular task stated by the customer. An

application is configured dynamically, depending on

which agents are active and accessible at this

particular moment. Map agents can display different

areas from a variety of digital maps (raster or vector

based maps, maps with different colour schemes,

etc). Reasonably short response time of the agent

system is achieved due to carefully designed

network traffic, combined with caching and parallel

processing of source maps and databases in the

servers. Agents, and the applications that use

services provided by agents are not in one-to-one

relation; one agent can simultaneously work with

many applications. Also, an application may use

services from different agents in different situations.

The map-specific part of the web browser’s page

in a customer’s computer is map_object (presented

as ActiveX component). The other parts of the page

depend on the specific requirements of the applica-

tion and cater for dynamic support of the page, and

for interactions between the map_object, the

customer, and web-servers. To display the requested

area of a map the map_object requests the necessary

parts of the map from appropriate agents, the request

may also contain additional details and/or

constraints. Typically the whole page or parts of it

are generated by a web-server based application (see

Figure 2). The main operational response and

support to the queries from the map_object and the

web-server application comes from a dedicated

multi-agent system.

Web-browser

of a customer

A web page

(HTML + JavaScript)

A map frame

Map component

(ActiveX)

Queries

(HTTP)

Web server

Web pages

(HTML + scripting)

Agents in one or many

networked computers

AMS

Specific

queries

(HTTP)

responses

(XML)

Interacting map, object

and information agents

Databases

Figure 2

The community of basic geospatial agents forms the

kernel of any particular agent-based digital map. The

collection of agents is easily extendable depending

on tasks required by the customer, types of digital

base-maps and additional databases to be used, etc.

Agents have generic features that facilitate their

application in a variety of applications with minimal

modifications.

Agent Application (WinA)

Main Window

main()

Run()

AGENT

Manager

Actor

Monitor

Report

Config_

file

.xml

Services

events

Network

traffic

Communication with

physical world

Figure 1: Generic description of an agent.

ON GEOSPATIAL AGENTS

211

For pilot application there are implemented

following classes of generic agents:

(1) Map agents transmit fragments of the map, an

agent can offer one or more raster base-maps.

(2) Vector agents transmit vector layers or

fragments of layers, if possible.

(3) Agent that transmit additional information in

one of the two possible formats – XML- record

or a picture, sound- or video file

The requirements on additional information are

obviously application-specific. Sample cases are

listed in the following in order to illustrate the

approximate character of the additional information:

(a) information regarding a graphical primitive,

(b) information on a certain location in a map

response to the queries for additional

information may contain several large volume

objects (pictures, sound- or video files); the

customer can later choose suitable information.

4 EXPERIENCE

4.1 Participatory GIS

Participatory GIS for regional planning and

management was tested as an application example.

The aim of the application created for Tartu City is

to view and update (as a dynamic collection of

spatial and information frames integrated into one

application) the information distributed in databases

of different owners.

The task came from the city government, who

needs the information of different infrastructures

(gas-, water-, sewage-, heating pipelines, power

lines and phone lines) for planning activities every

day. In reality, the infrastructure is maintained by

different organizations and the information,

therefore, is also kept in different GIS and databases.

The prototype of the participatory GIS for the

tasks described above is implemented as a federation

of agents. This agent-based system provides the

updated information from different GIS and DB as

well as represents and manages the information

supplied by agents involved.

User can select one main theme and compare it

with different subthemes. The number of base maps

(provided by map agents) and different data

categories (provided by vector agents) used in

application depend on maps and data which are

available for users. As a result, users can have

overview of a set of infrastructure of the area they

are interested, e.g. the location of pipelines,

availability of gas line or central heating system etc.

First experience shows that dynamic compilation of

frames intermediated by agents, offers reasonable

processing speed, better than that of a typical fixed

menu of web services of a traditional GIS.

Figure 3: Participatory GIS.

WEBIST 2005 - INTERNET COMPUTING

212

4.2 Tracking active objects

To include active or mobile objects in the

framework of geospatial agents, a prototype for

tracking vehicles was developed. As usually, a GPS

module, which is attached to moving object, receives

the signal from satellites and transmits the

coordinates with the unique ID of object to operator

agent. The agents provide the coordinate info of

particular object to map application. The map

application is built up as any other agent-based

application and active object acts as additional

agent.

The tracking multi-agent is a federation of

agents, consists agents of following types:

• agents processing fragments of the map;

• agents for searching, processing, and sending

the vector information for the image or situation

that has been activated in the map_object

• GPS agents, that in pair with periodically

transmit to other agents the position of active

objects equipped with standard GPS device.

• agents that manage, search, and forward

additional information related to active objects.

5 CONCLUSIONS

The developed collection of agent classes forms the

basis of agent-based digital maps. The collection is

extendable and depends on tasks required by the

customer, types of digital base-maps, additional

databases to be used, and on other factors. Each

agent is to be programmed as required by the

specific application. Agents have generic features

that facilitate their usage in a variety of applications

with minimal modifications. The experience shows

that dynamic compilation of agents’ intermediated

map frames offers a reasonable processing speed,

better than that of a typical fixed menu of web

services of a traditional GIS.

In contrast to the traditional approach in GIS, the

geospatial agents empower developers and end-users

to build their custom maps independently and post

useful information for their clients. Advantages

include the shift of ownership from digital map and

GIS suppliers to the users and the opportunity for the

users to build their own dynamic and interactive

maps. This opens a venue for developing many more

and tailor-made applications.

The described agent-based solution provides the

basic ideology that can be extended for application

on mobile & thin platforms. Further experiments and

the development of the instrumental software and

classes of geospatial agents are planned, in pair with

carefully selected geospatial application areas.

ACKNOWLEDGMENTS

This research has been partially financed by

Estonian Science Foundation grant no. 4860, and by

grants no. 014 2509s03 and no. 018 2565s03 from

the Estonian Ministry of Education and Research.

This support is gratefully acknowledged.

REFERENCES

Bigus, J.P., Schlosnagle, D.A., Pilgrim, J.R., Mills, W.N.,

Diao, Y., 2002. ABLE: A toolkit for building multi-

agent autonomic systems. IBM Systems Journal, vol.

41, no. 3, 350-371.

McKee, L., 2003a. The Importance of Going “Open”.

Open Geospatial Consortium, White paper, 8 p.

www.opengis.org

McKee, L., 2003b. The Spatial Web. Open Geospatial

Consortium, White paper, 8 p. www.opengis.org

Motus, L., Meriste, M., Kelder, T, Helekivi, J., 2004.

Agent-based Templates for Implementing Proactive

Real-time Systems. Proc. Int. Conf. on Computing,

Communications and Control Technologies, Austin,

Texas, ISBN: 980-6560-17-5, 199-204.

Odell, J., Parunak, H., Fleischer, M., 2003. Modeling

agent organizations using roles. Software and Systems

Modeling. Springer, vol. 2, 76-81.

Figure 4: Tracking active objects.

ON GEOSPATIAL AGENTS

213