Brazier, F.M.

Mobach, D.G.A.

Overeinder, B.J.

Splunter, S. van

Steen, M.R. van

Wijngaards, N.J.E.

DSpace at VU

AgentScape: Middleware, Resource Management, and
Services
F.M.T. Brazier, D.G.A. Mobach, B.J. Overeinder
S. van Splunter, M. van Steen and N.J.E. Wijngaards
Intelligent Interactive Distributed Systems Group and Computer Systems Group
Department of Computer Science, Vrije Universiteit Amsterdam
http://www.iids.org/
Abstract
The AgentScape project is geared to support large-
scale distributed systems at three levels: middle-
ware, services, and applications. This extended ab-
stract presents the basic AgentScape architecture,
resource management, and one specific service for
code mobility in more detail.
1 Introduction
The AgentScape project aims to support large-scale
distributed systems. The project encompasses three
well-defined research areas: (i) the AgentScape
middleware, (ii) services in AgentScape, and (iii)
applications designed and implemented in the
AgentScape environment.
Large-scale distributed systems are often hetero-
geneous systems: heterogeneous with respect to the
host architecture (Sun SPARC, Intel x86/i64), the
supported operating system (Solaris, Linux, Win-
dows NT), and the communication infrastructure
(bandwidth and latency). The major challenge in
the AgentScape project is to realize a scalable, se-
cure, and fault tolerant system, that supports multi-
ple distributed applications, heterogeneity, and mul-
tiple qualities of services.
AgentScape specifically deals with large-scale
distributed systems on which, mobile, autonomous
processes run. The mobile, autonomous processes
are called agents, the passive, possibly distributed,
entities are called objects. An important character-
istic of agents, which distinguishes them from tradi-
tional processes, is autonomy: agents are in control
of their own behaviour. From a management point-
of-view, this has implications for the management of
these mobile autonomous processes.
This extended abstract presents the middleware,
resource management, and one specific service for
code mobility in more detail.
2 AgentScape Operating System
The AgentScape operating system (AOS) provides a
platform with which mobile, autonomous processes
(agents) can be managed. It is, in fact, a virtual
machine distributed over a wide-area network con-
sisting of heterogeneous hosts. AOS kernels host
agents, objects, and provides service access (see
Fig. 1). All calls are filtered by the middleware and
appropriate calls are dispatched to the underlying
operating system, services, etc.
A location in the distributed system is a set of
hosts run by a single administrative entity. Each
host runs a minimal AOS kernel, and zero or
more agent servers, objects servers, and service ac-
cess providers. An agent server hosts agents, an
object server hosts objects, and a service access
provider makes external services accessible within
AgentScape. A location is implemented by the dis-
tributed AOS kernels, the agent servers, the object
servers, and service access providers.
The current architecture for this system is a mid-
dleware layer, on top of which agent applications
and agent platforms can be developed (see Fig. 1).
The current prototype implements the basic func-
tionality required.
Object
Server
Agent
Server
Agent
Server
AgentScape OS Kernel
R
es
ou
rc
e
agent
container
management
M
an
ag
em
en
t
Se
rv
ice
s
D
ire
ct
or
y
security
module module
comm.
module
bind protocol location
services
migration
module
module
life cycle
table
agent/process
AgentScape
API
Figure 1: AgentScape middleware architecture.
3 Resource Management
AgentScape’s resource management system, based
on the OSI management model, needs to be able to
to regulate agents without interfering with their au-
tonomy.
The OSI management model defines five func-
tional management areas: performance, secu-
rity, fault-tolerance, accounting, and configuration.
These areas can also be applied to the management
of multi-agent systems such as AgentScape:
• Performance management: managing the re-
source usage of agents on hosts within a multi-
agent system.
• Security management: ensuring security of
both agents and hosts in a multi-agent system.
• Fault-tolerance management: ensuring the
availability of agents and objects within a
multi-agent system, as well as the multi-agent
system as a whole.
• Account management: maintaining administra-
tive information about the agents within a sys-
tem.
• Configuration management: managing the con-
figuration of agents and objects that are under
management control.
The management system in the AOS needs to cre-
ate, delete, migrate, etc., agents. An agent life-cycle
model forms the basis for the definition of these op-
erations on agents by defining states of the agent and
transitions between these states. The central state in
the life-cycle model is the suspended state, in which
the agent is inactive and can be manipulated. This is
in contrast to other life cycle models for agents, in
which the active state of an agent is the central state.
4 Services
One specific AgentScape service extends the ba-
sic mobility of agents to true heterogeneous envi-
ronments, i.e., different operating systems, differ-
ent agent platforms, and different programming lan-
guages. The service that makes this possible is
called the Agent Factory of which a number of pro-
totypes have been implemented.
Mobile code is often not optimized for a wide va-
riety of heterogeneous hosts (including differences
in operating systems, hardware configuration, and
available resources). Rewriting mobile code for each
host encountered in the network, is not a feasible
solution, requiring too much effort from system ad-
ministrators and developers.
The Agent Factory service automatically adapts
mobile code to a specific host: a form of generative
mobility. In this approach, the mobile code need not
be sent to another host, but a blueprint of the mobile
code’s functionality is sent, together with informa-
tion needed to resume work. At each host, a service
is available which inspects a blueprint and gener-
ates the corresponding program code. The program
code generation process uses libraries of “building
blocks” to reconfigure agents.
An additional advantage of regenerating mobile
code, is that the risk of malicious behaviour (or ac-
quiring viruses en route) is reduced by regenerating
the mobile code, e.g., using trusted libraries of build-
ing blocks. The data (state) of the mobile code may
also be inspected, if required.
About the Authors
Frances Brazier is a full professor in the Intelli-
gent Interactive Distributed Systems group at the
Vrije Universiteit Amsterdam. Benno Overeinder
and Niek Wijngaards are assistant professors in this
group which focuses on the interdisciplinary area be-
tween Computer Systems and Artificial Intelligence.
Sander van Splunter and David Mobach are PhD stu-
dents in the same group. Maarten van Steen is a
full professor in the Computer Systems group at the
same university. The authors are grateful to Andy
Tanenbaum and Etienne Posthumus for their signifi-
cant contributions to this research and Stichting NL-
net for their financial support.
More Information
[1] F.M.T. Brazier, B.J. Overeinder, M. van Steen,
and N.J.E. Wijngaards. Agent factory: Gen-
erative migration of mobile agents in heteroge-
neous environments. In Proceedings of the 2002
ACM Symposium on Applied Computing (SAC
2002), pages 101–106, Madrid, Spain, March
2002.
[2] F.M.T. Brazier, M. van Steen, and N.J.E. Wijn-
gaards. On MAS scalability. In Proceedings
of the Second International Workshop on Infras-
tructures for Agents, MAS, and Scalable MAS,
pages 121–126, Montreal, Canada, May 2001.
[3] M. van Steen, P. Homburg, and A. S. Tanen-
baum. Globe: A wide-area distributed system.
IEEE Concurrency, 7(1):70–78, January–March
1999.
[4] N.J.E. Wijngaards, B.J. Overeinder, M. van
Steen, and F.M.T. Brazier. Supporting Internet-
scale multi-agent systems. Data and Knowledge
Engineering, 2002. in press.


AgentScape: Middleware, Resource Management, and Services

van Splunter, S.

van Steen, M.R.

NARCIS 

VU Research Portal

VU Research PortalAgentScape: Middleware, Resource Management, and ServicesBrazier, F.M.; Mobach, D.G.A.; Overeinder, B.J.; van Splunter, S.; van Steen, M.R.;Wijngaards, N.J.E.published inProceedings of the 3rd International SANE Conference (SANE 2002)2002document versionPublisher's PDF, also known as Version of recordLink to publication in VU Research Portalcitation for published version (APA)Brazier, F. M., Mobach, D. G. A., Overeinder, B. J., van Splunter, S., van Steen, M. R., & Wijngaards, N. J. E.(2002). AgentScape: Middleware, Resource Management, and Services. In Proceedings of the 3rd InternationalSANE Conference (SANE 2002) (pp. 403-404).General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            • Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            • You may not further distribute the material or use it for any profit-making activity or commercial gain            • You may freely distribute the URL identifying the publication in the public portal ?Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.E-mail address:vuresearchportal.ub@vu.nlDownload date: 23. May. 2021AgentScape: Middleware, Resource Management, andServicesF.M.T. Brazier, D.G.A. Mobach, B.J. OvereinderS. van Splunter, M. van Steen and N.J.E. WijngaardsIntelligent Interactive Distributed Systems Group and Computer Systems GroupDepartment of Computer Science, Vrije Universiteit Amsterdamhttp://www.iids.org/AbstractThe AgentScape project is geared to support large-scale distributed systems at three levels: middle-ware, services, and applications. This extended ab-stract presents the basic AgentScape architecture,resource management, and one specific service forcode mobility in more detail.1 IntroductionThe AgentScape project aims to support large-scaledistributed systems. The project encompasses threewell-defined research areas: (i) the AgentScapemiddleware, (ii) services in AgentScape, and (iii)applications designed and implemented in theAgentScape environment.Large-scale distributed systems are often hetero-geneous systems: heterogeneous with respect to thehost architecture (Sun SPARC, Intel x86/i64), thesupported operating system (Solaris, Linux, Win-dows NT), and the communication infrastructure(bandwidth and latency). The major challenge inthe AgentScape project is to realize a scalable, se-cure, and fault tolerant system, that supports multi-ple distributed applications, heterogeneity, and mul-tiple qualities of services.AgentScape specifically deals with large-scaledistributed systems on which, mobile,autonomousprocesses run. The mobile, autonomous processesare called agents, the passive, possibly distributed,entities are called objects. An important character-istic of agents, which distinguishes them from tradi-tional processes, is autonomy: agents are in controlof their own behaviour. From a management point-of-view, this has implications for the management ofthese mobile autonomous processes.This extended abstract presents the middleware,resource management, and one specific service forcode mobility in more detail.2 AgentScape Operating SystemThe AgentScape operating system (AOS) provides aplatform with which mobile, autonomous processes(agents) can be managed. It is, in fact, a virtualmachine distributed over a wide-area network con-sisting of heterogeneous hosts. AOS kernels hostagents, objects, and provides service access (seeFig. 1). All calls are filtered by the middleware andappropriate calls are dispatched to the underlyingoperating system, services, etc.A location in the distributed system is a set ofhosts run by a single administrative entity. Eachhost runs aminimal AOS kernel, and zero ormore agent servers, objects servers, and service ac-cess providers. An agent server hosts agents, anobject server hosts objects, and a service accessprovider makes external services accessible withinAgentScape. A location is implemented by the dis-tributed AOS kernels, the agent servers, the objectservers, and service access providers.The current architecture for this system is a mid-dleware layer, on top of which agent applicationsand agent platforms can be developed (see Fig. 1).The current prototype implements the basic func-tionality required.ObjectServerAgentServerAgentServerAgentScape OS KernelResourceagentcontainermanagementManagementServicesDirectorysecuritymodule modulecomm.modulebind protocol locationservicesmigrationmodulemodulelife cycletableagent/processAgentScapeAPIFigure 1: AgentScape middleware architecture.3 Resource ManagementAgentScape’s resource management system, basedon the OSI management model, needs to be able toto regulate agents without interfering with their au-tonomy.The OSI management model defines five func-tional management areas: performance, secu-rity, fault-tolerance, accounting, and configuration.These areas can also be applied to the managementof multi-agent systems such as AgentScape:• Performance management: managing the re-source usage of agents on hosts within a multi-agent system.• Security management: ensuring security ofboth agents and hosts in a multi-agent system.• Fault-tolerance management: ensuring theavailability of agents and objects within amulti-agent system, as well as the multi-agentsystem as a whole.• Account management: maintaining administra-tive information about the agents within a sys-tem.• Configuration management: managing the con-figuration of agents and objects that are undermanagement control.The management system in the AOS needs to cre-ate, delete, migrate, etc., agents. An agent life-cyclemodel forms the basis for the definition of these op-erations on agents by defining states of the agent andtransitions between these states. The central state inthe life-cycle model is the suspended state, in whichthe agent is inactive and can be manipulated. This isin contrast to other life cycle models for agents, inwhich the active state of an agent is the central state.4 ServicesOne specific AgentScape service extends the ba-sic mobility of agents to true heterogeneous envi-ronments, i.e., different operating systems, differ-ent agent platforms, and different programming lan-guages. The service that makes this possible iscalled the Agent Factory of which a number of pro-totypes have been implemented.Mobile code is often not optimized for a wide va-riety of heterogeneous hosts (including differencesin operating systems, hardware configuration, andavailable resources). Rewriting mobile code for eachhost encountered in the network, is not a feasiblesolution, requiring too much effort from system ad-ministrators and developers.The Agent Factory service automatically adaptsmobile code to a specific host: a form of generativemobility. In this approach, the mobile code need notbe sent to another host, but a blueprint of the mobilecode’s functionality is sent, together with informa-tion needed to resume work. At each host, a serviceis available which inspects a blueprint and gener-ates the corresponding program code. The programcode generation process uses libraries of “buildingblocks” to reconfigure agents.An additional advantage of regenerating mobilecode, is that the risk of malicious behaviour (or ac-quiring viruses en route) is reduced by regeneratingthe mobile code, e.g., using trusted libraries of build-ing blocks. The data (state) of the mobile code mayalso be inspected, if required.About the AuthorsFrances Brazier is a full professor in the Intelli-gent Interactive Distributed Systems group at theVrije Universiteit Amsterdam. Benno Overeinderand Niek Wijngaards are assistant professors in thisgroup which focuses on the interdisciplinary area be-tween Computer Systems and Artificial Intelligence.Sander van Splunter and David Mobach are PhD stu-dents in the same group. Maarten van Steen is afull professor in the Computer Systems group at thesame university. The authors are grateful to AndyTanenbaum and Etienne Posthumus for their signifi-cant contributions to this research and Stichting NL-net for their financial support.More Information[1] F.M.T. Brazier, B.J. Overeinder, M. van Steen,and N.J.E. Wijngaards. Agent factory: Gen-erative migration of mobile agents in heteroge-neous environments. InProceedings of the 2002ACM Symposium on Applied Computing (SAC2002), pages 101–106, Madrid, Spain, March2002.[2] F.M.T. Brazier, M. van Steen, and N.J.E. Wijn-gaards. On MAS scalability. InProceedingsof the Second International Workshop on Infras-tructures for Agents, MAS, and Scalable MAS,pages 121–126, Montreal, Canada, May 2001.[3] M. van Steen, P. Homburg, and A. S. Tanen-baum. Globe: A wide-area distributed system.IEEE Concurrency, 7(1):70–78, January–March1999.[4] N.J.E. Wijngaards, B.J. Overeinder, M. vanSteen, and F.M.T. Brazier. Supporting Internet-scale multi-agent systems.Data and KnowledgeEngineering, 2002. in press.

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