Object Oriented Distributed Virtual Systems Framework (2004­2014)(OODVS Framework,Remote Method Invocation, Multicast Remote Method Invocation, Intelligent Handlers, Proxy

Methods, Threaded Methods, Migratory Objects, Distributed System, Shared State)Diego Malpica Chauvet et al.

Praxis (www.openknowledge.mx), diego­malpica@openknowledge.mxAbstractIn this paper, we propose a framework following the Paradigm Shifting Technique focused on using advance objectoriented languages features to reduce the external complexity inherent to distributed systems.Categories and Subject Descriptors: C.2.4 Distributed Systems1 IntroductionOriginally, the development of Distributed Virtual Reality was strongly promoted by the military industry, mainly for theelaboration of combat simulators. This industry has devoted a lot of resources to developing quality software allowing forreuse compatibility and portability of components, emphasizing the protection of previous investment. Today, thedevelopment of virtual reality is more diverse, due to develop in new areas such as entertainment, medicine andmanufacturing. Many new technologies have been arrived since DIS(Distributed Interactive Simulation) protocol origin inin 1980.

Paradigm Shiftingfrom 1980 to 2013

2005 BUP & EPF

Virtualization

Mobile

WWW

CPU(Hardware)

OperativeSystem

Languages

Frameworks

DataBase

Presentation

Architecture

Quality

Applications

Social Technologies

1979 Unix

1981 MS­DOS

1966 DOS

1985 Windows

1991 Linux

2007 Linux Android

1993 Newton

1988 Mac

2004 Linux­Ubuntu

1978 80861982 286

1993 Pentium

2006 Dual Core2007 Quad Core

2011 10 Core

1988 SUN softpc

1979 IBM VM

1997 MAC virtualpc

1998 VMWare

2003 XEN

2008 KVM

1993 Newton

2007 Kindle 2010 Ipad2011 Galaxy

2007 IPhone2007 Android

1991 HTML

1995 AWT

1999 JSP

2002 Vaadin

1992 OpenGL

2006 GWT 1.0

2004 JSF 1.0

1993 Mosaic

1994 Newton1994 Netscape

1996 Safari1998 Firefox

1995 IExplorer

2011 BBerry

2011 FFox M

2011 Chrome

2007 Safari M2008 Android M

2008 Chrome2009 Opera M

2001 Explorer M1996 Apache

1987 CMM

1989 ITIL

1991 SCRUM1993 MSF

1999 XP

2003 RUP

1998 ASP

1996 Flash

2007 SilverLight

1999 GPU

2013

1996 Palm

2000 PocketPC2001 Win XP

2009 Win 7

1996 Win NT

1987 OS/2

1984 GNU

2008 Atom

2002 CMMI

1990 WWW 2000 PocketPC

1960

1980

1990

2000

2010

2011 Chrome M

2009 GWT 2.02007 Vaadin/GWT

1970

2000

2010

1990

1960

1980

1970

1975 Tandem

1991 Tandem­Mips

2001 Tandem­Itanium

1975 Tandem T/TOS

1994 Tandem OSS (Unix)

2006 JSP­JSTL

2000 HTML 4

2008 HTML 5

1980

2006 Linux 2.4

2011 Linux 3.0

2001 MAC OS 10

2012 MAC OS 10.8

2004

2009 JSF 2.0

1997 WAP

2013 Vaadin 7

1970 DBMS1978 RDMS

1979 Oracle

1997 Oracle ORDBMS

1994 Mysql

2004 DB4O

2001 HSQL

2005 H2

1980 OODMS

1988 Oracle RDBMS

1979 MVC

1980 OSI

1998 XML

1981 RPC

1996 DCOM

1997 RMI

1998 SOAP

2000 REST

2007 Cloud

2000 Ajax

1997 MVP 1987 Sybase RDBMS

1989 Microsoft SQL

1967 Object Oriented

1983 Internet

1970 Chat1970 Enail

1991 WWW­3 Layer

2002 RIA

2002 Prevayler

1972 C1972 SQL

1983 C++

2001 AspectJ2001 C#2003 Scala

1999 J2EE2000 .NET

2001 Hibernate2006 OpenJDK2005 Harmony

1967 Simula

1968 BI

1980 BPMS

1970 Ecommerce

1984 Staroffice1989 MS office1990 ERP

2000 OpenOffice

2006 Google Docs

2011 MS Off365

2000 RSA Public

1991 ISO­S. Engineering1993 ISO­S. Process

1960 RFC

1950 Freesoftware

1970 BBS

1958 Lisp1959 Cobol

2007 Clojure

2004 BPMN

2004 OODVS2002 Spring2000 Liferay

1991 MS Visual Basic

2004 Eclipse

1991 MS Power Builder

2012Win Phone 8

1985 MacApp

1995 Java

1996 Cocoa

1991 MS Visual Basic

1995 Wikis1997 Google

1998 Opensource1999 Sourceforge

2001 Wikipedia2003 Linkedin

2004 Facebook

1990 WWW

1995 MS Visual Studio

1997 Netbeans

1995 Java

1995 PHP1995 JavaScript

1997 UML

2012 Win 8, WinServer2012 Lunix U Unity

2012 Lunix Android 4.1

2008 Hyper­V

Granted ObsoleteOld and ValidTargetNew Promissing

1987 PAC

2009 Mongo DB

2007 Amazon EC2

2009 Windows Azure2009 Google Apps Engine

2010 OpenStack

2006 Twitter1999 RSS

2006 OpenUP

2001 OWASP & ISO­Security

1993 MSF

1993 EDI

2004 PCI

1990 Versant ObjecttDB

2007 Hadoop

2010 Maria DB

1980 DIS

1993 CORBA

2000 HLA

1998 Java 3D

1995 VRML

2004 Hypper Threading

1997 Swing

2001 Webstart

1995 Applets

2000 OSGi

Figure 1: Technology advances 1972­2013Shared state maintenance is governed by the Consistency­Throughput Trade­off that imposes physical limits on howconsistent state can be achieved within the given a set of constraints. Shared state is a complex issue. Selecting anappropriate shared state maintenance technique is an engineering task that must balance a variety of issues, includingbandwidth, computation, latency, data consistency, and reproduce­ability.There are three broad types of shared state maintenance:Shared repository: Uses a centralized database to store the net current state. It provides highly consistent statemaintenance at the expense of high bandwidth, slow throughput, and tight inter­dependencies among participatinghosts.Blind broadcast: Transmits updates on a regular basis. Sacrifices absolute consistency in favor of eventual consistencywhile reducing the inter­dependencies among participating hosts.Dead reckoning: Transmits non­regular updates and uses prediction and convergence to manage state at remote hosts.Provides weakly consistent state maintenance (bounded error) in order to minimize bandwidth and maximize hostautonomy.2 Technologies2.1 Java PlatformThe language is a key factor to our approach since the power of expression is directly related with the externalcomplexity. To see the language as the center of integration of multiple technologies (as a platform) it really simplifies

things just take a glance to the following table that’s shows the relevant technologies for our point of view integrated tothe java platform.

Version Technologies

Java 1.0 Object Oriented, Virtual Machine, Threads, Sockets, Garbage Collection, Dynamic Loading

Java 1.1 Just in time compilation, Serialization, Remote Method Invocation, Reflection

Java 1.2 Cryptography

Java 1.3 Proxies

Java 1.4 XML

Java 1.5 Annotations, Concurrency, Generics

Table 1: Java Platform relevant technologies2.2 Remote MethodsRMI (Remote Method Invocation) has been part of the Java Platform since version 1.2 unfortunately the currentimplementation has not fully take advantage of platform advances like reflection (proxy, annotations), and protocols(HTTP, UDP Broadcast, UDP Multicast).Since we consider this technology a key factor we have implemented our own remote method stack which it provides akind of RMI, RPC services that doesn’t need stubs, skeletons or an external tool. Currently we support various protocolsimplemented over HTTP/TCP and UDP (Broadcast and Multicast) and they have several security features based onBouncy Castle Cryptography API. The semantics are very similar to the RMI semantics, but designed to support theimplementation of the Proxy Model that we will see ahead.2.3 Intelligent HandlersHandlers could be seen as a kind of proxy that it’s placed between method invocations and the method execution. Ahandler in conjunction with other java features as reflection an annotation, can greatly simplify the design and thesemantics of the components. We used handlers to implement our remote method stack with out the need of externaltools and precompiled stubs or skeletons. We also used handler to implement the Proxy Model.2.4 Proxy ModelThe purpose of the model is to support objects and messages distribution. The model is constituted by three roles:Participant Entity and Proxy. The interaction between these roles defines a Distributed Virtual System.2.4.1 Role responsibilitiesParticipant

Holds the entitiesInteract with entities to update their proxiesInteract with the proxies to update statesInteract with other participants to distribute proxies

Propagate proxies between regionsSend heart beats to publish himself to other participants.Listen for other participants hear beats.Remove dead assumed participantsSend proxies of new entities to known participantsSend proxies of its entities to new known participantsProvides classes and resources to other participants

Entity

Contains state informationContains references to its proxy entitiesContains methods and Proxy methods

Proxy

Is an entity that’s has a parent entity.Contains a reference to a root entity.Could be the parent of other proxy entities.

Figure 2: Planes implemented using our Proxy Model and OpenGL, every window is a different participant; eachparticipant sees its entities and the proxies from other participant’s entities.

Figure 3: Illustrates the object distribution between five participants

Figure 4: Illustrates different visibility regions between the five participants of the figure 2.2.5 Proxy MethodsProxy methods are implemented via Handlers and they are used to propagate messages to the entities and all itsproxies.2.6 Time PerceptionThe time services allow to have different times and clock speeds and to mitigate network latency effects. They are used inconjunction with prediction and convergence algorithms like the Dead reckoning implemented in advanced examples.2.7 Dead ReckoningThe Proxy model eases the implementation of Predictive and Convergence algorithms the Proxy Model is a kind of deadreckoning general implementation.2.8 SecurityWe base our solution cryptography in the Bouncy Castle Light­weight API.2.9 Migratory ObjectsFull objects (code and data) are moved between participants a participant can retrieve code and resources on demandfrom other participants.3 Hands on Code3.1 Remote MethodsThese are the interface and class for the object to be used for remote method invocation in the next code fragments.

public interface ObjectExample_I

public String msg1(String name) throws Exception;

public class ObjectExample implements ObjectExample_I

public String msg1(String str) System.out.println(str);return "RE: "+ str ;

This is the server part; a remote method server is created and started. Then an object is created and added to the serverto be ready for remote invocations.RMServer server = new RMServer().start();server.putObject("O1", new ObjectExample());

This is the client part; a handler is created and used to perform the remote method invocation.RMClientContext cc = new RMClientContext("HTTP://localhost");ObjectExample_I handler = (ObjectExample_I) cc.getHandler(ObjectExample_I.class, "O1");String response = handler.msg1("Hello World.");3.2 Remote Method ProtocolsThese are the interface and class for the object to be used for remote method invocation in the next code fragments.

public interface ObjectExample_I

public String msg1(String name) throws Exception;

public class ObjectExample implements ObjectExample_I

public String msg1(String str)

System.out.println(str);return "RE: "+ str ;

This is the server part. This code part first creates and initializes the server. If the keyDir and keys that does not exist it willbe created.UDP information is specified as part of the initialization for UDP remote method invocations. Finally the server is started.An object is created and added to the server to be ready for remote method invocation.FileUtils.mkdirs("keyDir");RMServer server = new RMServer("keyDir", "masterPasswd", "serverPasswd");server.setUDPPort(9001);server.addCastAddress("224.0.0.1");server.start();server.putObject("O1", new ObjectExample());This is the client part, a RMClientContext is created and used to obtain handlers to perform remote method invocationsusing various protocols.RMClientContext context;context = new RMClientContext("HTTP://localhost", RMClient.RM_HTTP_V1_0, "keyDir", "clientPasswd");context.setUDPPort(9001);context.addCastAddress("224.0.0.1");ObjectExample_I handler;handler = (ObjectExample_I) context.getHandler(RMClient.RM_V1_0,ObjectExample_I.class, "/O1");handler.msg1("HTTP.");handler = (ObjectExample_I) context.getHandler(RMClient.RM_UDP_V1_0, ObjectExample_I.class, "/O1");handler.msg1("UDP.");handler = (ObjectExample_I) context.getHandler(RMClient.RM_HTTP_SIG_V1_0, ObjectExample_I.class, "/O1");handler.msg1("HTTP Signed.");handler = (ObjectExample_I) context.getHandler(RMClient.RM_HTTP_SEC_V1_0, ObjectExample_I.class, "/O1");handler.msg1("HTTP Signed and Encrypted.");3.3 Proxy ModelThese are the interface and the class used in the following code fragments.Two proxy methods are implemented, with names terminated with TCPP an UDPP that stands for TCP Proxy method and

UDP proxy method.public interface EntityExample_I public void printMsg_TCPP(String msg) throws RMClientException;public void printMsg_UDPP(String msg) throws RMClientException;public class EntityExample extends Entity implements EntityExample_I

public EntityExample(String name) throws RMClientException super(name);

public void printMsg_TCPP(String msg) throws RMClientException System.out.println(" Participant:" + getParticipantName() + " TCCP:" + msg);public void printMsg_UDPP(String msg) throws RMClientException System.out.println(" Participant:" + getParticipantName() + " UUDP:" + msg);The next code part creates a participant "A" and adds a Entity "A1" to it.A proxy handler of entity "A1" is obtained.The proxy handler is used to invoke the two proxy methods, the handler uses the prefix of the method name (UDPP,TCPP) to determine how to handle the method invocation.Participant a = new Participant("A").start();a.addEntity(new EntityExample("A1"));EntityExample_I handler= (EntityExample_I) a.getHandler("A1",0);handler.printMsg_UDPP("hello 1.");handler.printMsg_TCPP("hello 2.");The next code part creates a participant "B".Participants "A" and "B" will eventually discover each other and send proxies to each other.After participant "B" is created a proxy for the entity "A1", will be retrieved.Then the local method getName of the proxy will be invoked.Finally a proxy handler for the proxy "A1" will be obtained.Then the handler will be used to invoke the proxy method.Participant b = new Participant("B").start();EntityExample proxy = (EntityExample) b.getEntity("A1",0);String name=proxy.getName();handler = (EntityExample_I)proxy.getHandler();handler.printMsg_TCPP("hello 3.");4 ResultsThe framework substantially reduced the complexity associated to maintaining a shared state and the number ofspecialities needed to implement a Distributed Simulation.

Figure 5: Amatrol Robot implemented using Proxy Model and Java3D, every window is a different participant; eachparticipant sees its entities and the proxies from other participant’s entities.

Figure 6: Space Ship using Proxy Model and Java3D, every window is a different participant; each participant sees itsentities and the proxies from other participant’s entities.5 ConclusionThere are significant advances in various technologies that plenty justify a paradigm shifting in order to get new designsand implementations.6 Future WorkImplement a secure loader for the proxy Loader, an various secure protocols for the UDP messages.Introduce the use of annotations and Aspect oriented techiques for method handling instead of name prefixes.7 DownloadsHome page: http://oodvs.sourceforge.netProject page: http://sourceforge.net/projects/oodvs8 GlosaryOODVS Object Oriented Distributed Virtual SystemsRMI Remote Method InvocationRPC Remote Procedure CallTCP Transmission Control ProtocolUDP User Datagram Protocol (broadcast and multicast)HTTP HyperText Transfer ProtocolRSA A public­key encryption technologyRC4 A variable key­size stream cipherDead ReckoningDIS Distributed Interactive SimulationNPS Naval Postgraduate School9 References

1. Distributed Interactive Simulation (DIS­Java­VRML) http://faculty.nps.edu/brutzman/vrtp/dis­java­vrml/download.html

2. Open DIS http://open­dis.sourceforge.net/Open­DIS.html3. Open Astex Viewer http://openastexviewer.net/web/4. ITESM­CEM, Tesis, "Arquitectura para realidad virtual distribuida con física simulada, poblada de agentes

autónomos", Ing. Montserrat Morales, Ph. D Isaac Rudomín,

5. NPS, Tesis, "AN AUTOMATED APPROACH TO DISTRIBUTED INTERACTIVE SIMULATION (DIS)PROTOCOL ENTITY DEVELOPMENT", Michael Canterbury, September 1995.

6. NPS, "Dial­a­Behavior Protocol" (DBP)7. "Networked Virtual Environments and DIS­Java­VRML Library", NPSNET Research Group, Don Brutzman

and Mike Zyda8. NPS, " A NETWORK SOFTWARE ARCHITECTURE FOR LARGE SCALE VIRTUAL ENVIRONMENTS",

Michael R. Macedonia, Michael J. Zyda,David R. Pratt,Paul T. Barham,Steven Zeswitz9. NPS, " NPSNET ­ Large­Scale Virtual Environment Technology Testbed", Michael Zyda*, Don Brutzman,

Rudy Darken, Robert McGhee, John Falby, Eric Bachmann, Kent Watsen, Ben Kavanagh & RussellStorms