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Web-based Simulation
Course: 60-520
Instructor: Dr. A.K. Aggarwal
By Sheng Bai
Agenda
• Introduction
• Client-based
• Server-based
• Distributed
• Summary
• Reference
What’s Simulation
• Building a software
• Based on an algorithmic logic
• Simulate some phenomenon
• With some purpose
– Observing systems
– Finding analytical solutions
– Predicting system behaviors
Types of simulation
• Stochastic or deterministic
• Continuous or discrete
• Local or distributed
Web-based Simulation
• A driver of software technologies
• A rapidly emerging area
– WEBSIM;
– Winter Simulation Conference Sessions;
– WSC Modeling Methodology Track;
• Java
Classification
• Client-based
• Server-based
• Distributed
Client-based
• Browser & Server Structure
• Download logic to client side
• Running and analyzing on client’s side
• No communications during the simulation
• Implementation: simjava
simjava
• A discrete event simulation package
• A Java port of a C++ library, HASE++
• HASE++ is based on Jade’s SIM++
• A collection of entities:
•
•
•
Sim_entity
Entities are connected
by ports: Sim_port
Communication via
using event objects:
Sim_event
Central controller:
Sim_system
Process
Sim_system
Sim_entity
Source
Sim_system.add()
Sim_system.add()
Sim_port
.initialize()
Sim_entity
Sink
Sim_port
out
in
Sim_system.link_ports ("Sender", "out", "Receiver", "in");
Sim_system.run()
Animation
• Package: simanim;
• Class: Anim_applet;
• Method: Anim_applet.anim_init();
• Driven by trace output of simulation
– S traces
– P traces
Demonstration
Analyzing simulation results
• Package: simdiag
• Java Beans:
– TimingDiagram
– TraceSaver
– TraceLoader
– GraphDiagram
TimingDiagram
• Stat timing window in anim_init()
• Attach to a trace saver
• A TraceEventObject
– Trace line
– A command:
• TRACE; LAYOUT; RUN; PAUSE; STOP; DISPLAY
Example trace File
$types
State IDLE BUSY SEND RECV
$bars
p[0] State
p[1] State
$events
u:p[0] at 1.234: P IDLE
u:p[1] at 4.567: P BUSY
...
TimingDiagram
GraphDiagram
GraphDiagram
Problems
• Take time to download
• Unsteady performance
• Can’t run sophisticate simulations
Server side
• RMI (Remote Method Invocation)
– Distributed simjava
• EJB (Enterprise JavaBeans)
– JSIM
RMI Architecture
Process
Server
User Machine
RMI Runtime
Sim_system.link_ports ("Sender", "out", "Receiver", "in")
Source
Web Browser
Sim_systemRI
implements
Sim_systemRI
Sim_system
Sim_system.add()
Sim_system.add()
Client Applet
Sink
java.rmi.Remote
EJBs
• Independence form messaging
middleware, transaction support, naming
& directory services…
• Delegates difficult tasks to EJB server
• Simplify application development
Client-Server Interaction
JSIM Architecture
Simulation process
Distributed system
• EJB solution has all the tradition weakness
• Reuse
• Collaborate
Standardization
• High Level Architecture (DoD)
• Components based Architecture
• Runtime infrastructure (RTI)
– Federation management
– Declaration management
– Object management
– Ownership management
– Time management
– Data distribution management
Solution: Jini & XML + JSIM
• Jini: a universal network-computing model
• XML: a universal format for data exchange
Jini
• Java dynamic networking
• Distributed, highly adaptive to change
• Open software
• Originally created by Sun Microsystems
• Contributed to Jini Community in 1999
Jini Architecture
Base
Java
Java
+
Jini
Infrastructure
Programming
Model
Services
Java VM
Java APIs
JNDI
RMI
Java Beans
Enterprise Beans
Java Security
…
JTS
Discovery/Join
Leasing
Printing
Distributed
Security
Transactions
Transaction
Manager
Lookup
Events
JavaSpaces
Service
Infrastructure
• Distributed security
– Integrated into RMI,
– extends to world of distributed systems
• Discovery/Join protocol
– Allows services to discover, advertise
• Lookup service
– A repository of services
Programming Model
• Leasing interface
– Allocating and Freeing resources
• Event and notification interface
– Enabling Event-based communication
• Transaction interface
– Ensuring properly coordination of state
changes.
Services
• Builds on top of Infrastructure
• Has an interface defining its operations
• Both user and program oriented
• Examples:
– A printing service
– A JavaSpaces service
– A transaction manager
1. Discovery
2. Join
3. Lookup
Process4: Invoke
XML
• Self-descriptive, text-based, universal
• Two ways to access XML documents
– Element level: standard APIs
• Simple APIs for XML (SAX): efficient
• Document Object Model (DOM): flexible
– Object level: programmatic manipulation
• Java XML Data Binding project (Sun)
• Dynamic XML (Object Space)
JSIM Federated Simulation with Jini
and XML
Summary
• Three types
• A young discipline
• Reuse of existing simulation models
• Federated is the most promising one
Reference
• [1] Xeuqin Huang and John A. Miller, "Building a Web-Based Federated
•
•
•
•
Simulation System with Jini and XML," Proceedings of the 34th Annual
Simulation Symposium (ANSS'01), Seattle, Washington, United States, April
2001
[2] Z.Y. Du, “LBSim: A Simulation System for Dynamic Load-Balancing
Algorithms for Distributed Systems”, Technical Report in University of
Windsor, Canada, 2004.
[3] John A. Miller, Andrew F. Seila and Xuewei Xiang, "The JSIM WebBased Simulation Environment," Future Generation Computer Systems
(FGCS), Special Issue on Web-Based Modeling and Simulation, Vol. 17, No.
2 (October 2000) pp. 119-133. Elsevier North-Holland.
[4] Ernest H. Page, Robert L. Moose Jr. and Sean P. Griffn, “Web-based
simulation in simjava using remote method invocation”, Proceedings of the
29th conference on Winter simulation Atlanta, Georgia, United States, 1997
[5] Fred Howell and Ross McNab "simjava: a discrete event simulation
package for Java with applications in computer systems modelling", in proc.
First International Conference on Web-based Modelling and Simulation, San
Diego CA, Society for Computer Simulation, Jan 1998.
Questions?