Web Service Architecture for Mobile Computing

Web Service Architecture

for Mobile Computing

Sangyoon Oh

Outline

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Motivation

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Research Issues

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Our approach:

HandHeld Flexible Representation Architecture

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Performance Evaluation

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Conclusion

Web Service and Mobile Computing

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Web Service inter-relates distributed functionalities

(i.e. services) in an elegant and technology-neutral

manner.

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Mobile devices with wireless connections have

become a vital part of people’s everyday life.

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Play audio/video, Access Web, Multiplayer gaming through

wireless connection, participate in collaboration session.

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3G cellular network (

downloading up to 500kbps)

, 802.11b/g

Important Obstacles

in Integrating Web Services and Mobile

Computing

Some Current Approaches

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Compressing XML Document

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gzip, XMill

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Able to reduce a document size

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However, the additional layer required to

compress and to decompress

add a significant

overheads

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Attaching binary data to SOAP message

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MTOM/XOP: MIME attachment

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JPG, MP3: standardized format

Fast Infoset

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Specifies a representation of

an instance of the XML

Infoset using binary encoding.

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XML Infoset Specification is

used to refer information in well

formed XML.

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Doesn’t tied up with XML API

(e.g. DOM, SAX)

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Use ASN. 1. for binary

encoding

Fast Infoset: Example

<root

<tag>

one

</tag

<tag>

two

</tag

<anotherTag>

one

</anotherTag>

</root>

{0}

<root

{1}

<tag>

{0}

one

[1]

<>

{1}

two

{2}

<anotherTag>

[0]

1

tag

1

two

one

0

root

0

Content

Local Name

•No end tags

Motivation

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Performance has many aspects

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XML parsing and transmission overhead

often can not be

afforded

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A lot of research on message representation (e.g.

binary XML)

but not on the overall system

framework

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overcome or bypass possible performance overheads

required to support optimizing messages

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Security can be important and impact performance

Research Issues

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Architecture of Interaction of mobile client

and Web Service.

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A negotiation architecture that allows protocol

independent solutions

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A data description language that allows

conversion between multiple representations

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Adopt database semantics to reduce

Our approach:

HandHeld Flexible

Our Approach: HHF

Three Key Design Features

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Distinguishes between message semantics and syntax

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Using

data description language

e.g.

Data Format Description

Language (DFDL) style

Simple_DFDL

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Exchange messages in a

streaming

style

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Use streaming at protocol and semantic level

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Using Context-store to hold static data

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Unchanging/redundant SOAP message parts

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Simple_DFDL as a data representation

Messaging Style

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Producer and Consumer of data have access

to its Schema (Static data binding)

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Stream -- set of related messages

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Messages in the stream



the same structure

and same data type

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Mobile clients (e.g. PDAs or smart phones)

access to Grid job

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Message size is tend to be small (e.g. in

mobile computing)

Distinguishing

XML Syntax and Semantics

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Our XML data model is defined by XML

Infoset specification.

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Our approach

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Distinguish semantic (message content) and

syntax

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e.g. <year>2006</year>

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Its syntax and value, 2006

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To define the XML syntax

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Use a data description language (Simple_DFDL )

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Use a data description file as a sample instance of messages

Simple_DFDL

and Processing Module

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Mapping data between representations

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Processing architecture

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Simple_DFDL describes data format

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Processor (DSParser) builds the HHFR Data model

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Filter converts data from and to the preferred

representation format

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A follow-on project is to integrate HHFR with

fully developed DFDL

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HHFR starts with Simple_DFDL and will move to DFDL.

Example

Simple_DFDL document

<xs:element name="HHFR">

<xs:complexType>

<xs:element name=“Float1" type=“float"/>

<xs:element name=“Float2" type=“float"/>

</xs:complexType>

Message Handling

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Filters

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Convert representations

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XML-to-binary, binary-to-language specific data model

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Handler for Headers

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Conventional Handler Approach: Convert back to SOAP

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Make a handler understand alternative representation

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e.g. WS-RM handler could be taught alternative representation

Negotiation Process

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Use conventional SOAP message

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Negotiate

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HHFR-Capability

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A preferred representation

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Characteristics of Stream

Streaming Related Issues

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Transport:

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HTTP transport could be a performance

bottleneck



well known fact

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TCP/IP connection setup overhead, Request/Response.

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Persistent Connection may be not guaranteed in Cellular

environment

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Representation:

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Using Context-store saving of redundant /

unchanging data

Context-store

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Strategy: archiving static meta-data and

negotiated information

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Any WS enabled Database could be used

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Guarantees semantically persistent recovery

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WS-Context specification

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Use URI to store and retrieve

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Fault Tolerant High Performance Information

Normal Runtime Scenario

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A HHFR-capable endpoint sends a negotiation request

to intended service endpoint over SOAP.

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Send an input data description

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Service endpoint sends an output data description

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Two endpoints exchange message in stream fashion

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Messages in the stream are in the form of negotiated

representations

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The redundant / unchanging static metadata and

negotiation details are stored in Context-store

Summary

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Bandwidth problems in limited wireless connection

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Optimized message representation

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Reducing message size using Context-store

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Parsing & Serializing overhead to less powered

processor in mobile device

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Avoiding conventional SOAP processing

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Simple_DFDL & Filters process message in efficient way.

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HTTP request/response in high latency wireless

connection

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Transport level message streaming

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Intermittent Wireless Connection

Performance Evaluation

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Experiments are intended to show

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Performance comparisons between a

conventional SOAP based client and a HHFR

based client

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Savings and gains from Context-store

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Analyzed optimal scalability using Context-store

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Service clients are running on Treo600

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Experiments run through actual 2G cellular

Connection Setup

Machine Configuration

Axis 1.2 (in Tomcat 5.5.8)

SOAP Engine

Java 2 platform, Standard Edition

(1.5.0-06)

Java Version

GNU/Linux (kernel release 2.4.22)

OS

100Mbps

Network Bandwidth

2GB total

RAM

Intel® Xeon™ CPU (2.40GHz)

Processor

Service Provider: Grid Farm 8

14.4Kbps (Sprint PCS Vision)

Network Bandwidth

32MB total, 24MB user available

RAM

ARM (144MHz)

Processor

System Parameters

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t

: time per message in a HHFR performance model

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t

: time per message in a conventional SOAP performance model

O

: overhead for accessing the Context-store Service

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O

: overhead for negotiation

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C

: total time for finishing stream of the HHFR

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C

: total time for finishing stream of the conventional SOAP framework

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C

_hhfr

= nt

_hhfr

+ O

_a

+ O

_b

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C

_soap

= nt

_soap

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Breakeven point:

n

be

t

hhfr

+ O

a

+ O

b

=

n

be

t

soap

O

a

(WS) is roughly 20 milliseconds

Performance Model and Measurements

0.825

5.133±0.036

Negotiation (

Ob

)

0.516

4.127±0.042

Context-store Access (

Oa

)

Stddev (sec)

Average±error (sec)

O

a

: overhead for accessing the

String Concatenation

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Measure the total

stream time i.e.

summation of RTT

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Independent

variables

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Number of

messages per

stream

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Size of the

message

Floating Point Number Addition

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Large Slope of

SOAP

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high latency of

the HTTP

based

communication

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SOAP parsing/

serialization

overhead

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There exist in

Performance

saving by using Context-store

0.538

2.81±0.098

0.867

5.20±0.158

Large: 2.61KB (sec)

0.217

1.75±0.040

0.187

2.76±0.034

Medium: 513byte (sec)

Stddev

Ave.±error

Stddev

Ave.±error

Optimized Message

Full SOAP Message

Message Size

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Experiments ran over HHFR

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Optimized message exchanged over HHFR after saving

redundant/unchanging parts to the Context-store

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We use WS-Addressing message for the experiment.

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Save on average 83% of message size, 41% of transit time

Summary of the Round Trip Time (

T

)

System Parameters

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N: the maximum number of stream supported by

one server

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T

_wsctx

: time consumed to process (setContext) an

operation

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T

_{time-in-server}

: time consumed in Axis server

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T

_{axis-overhead}

: time consumed to process Axis

data-binding and HTTP request/response

Summary of T

time-in-server

measurements

Ttime-in-server

= Twsctx

+ Taxis-overhead

Twsctx

=< 1 milliseconds

Axis 1.2 Beta3 is used

Data binding overhead

at Web Service Container

is the dominant factor to

message processing

Allowed Maximum Number of Stream

by Server

N: the maximum number of stream supported by one server

3N/T

≈ 1 / T

(N/T stream starts and N/T stream ends)

N ≈ T

/ (3 * T

)

e.g. T

= 600 (sec),

T

= 0.035 (when the context-size is 1.2 Kbyte)

N ≈ 600 / {3 * 0.035}

N ≈ 5700

Conclusion

Summary of Contributions

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Design and implement an overall system framework architecture:

The HHFR Architecture provides

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A mechanism to negotiate the characteristics of a stream

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A streaming communication channel

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Simple_DFDL which distinguishes the semantics from the

representation of message content

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An interface to Information service (Context-store)

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A semantically persistent recovery framework

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Detailed performance evaluation

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Benchmark applications, approach to use a Context-store

Future work

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Streaming channel integrated with a Web Service

Container.

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Provide a plug-in API for filter implementation

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Integration with fully developed DFDL

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Support more message type

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Secure Message stream using negotiation process

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Bouncy Castle lightweight cryptography package

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WS-Policy specifying the default strategy

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Read from Context-store or negotiation message

Related publications

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Sangyoon Oh

and Geoffrey Fox, “Optimizing Web Service Messaging

Performance in Mobile Computing,”

Future Generation Computer Systems

Journal

, Revision being processed.

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M. Aktas,

S. Oh

, G. Fox, and M. Pierce, “XML Metadata Service”

Proc. of the

IEEE 2

_{International Conference on Semantics, Knowledge and Grid}

(SKG2006)

, Nov. 2006

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Sangyoon Oh

, Mehmet Aktas, Marlon Pierce, and Geoffrey Fox, “Architecture

for High-Performance Web Service Communications using an Information

Service,”

World Scientific and Engineering Academy and Society Transactions

on Information Science and Applications

, May 2006

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Sangyoon Oh

, Hasan Bulut, Ahmet Uyar, Wenjun Wu, and Geoffrey Fox,

“Optimized Communication using the SOAP infoset For Mobile Multimedia

Collaboration Applications,”

Proc. Of the IEEE 2005 International Symposium on

Collaborative Technologies and Systems (CTS 2005)

, May 2005.

Full list of publications (I)

l Wonil Kim, Sangyoon Oh, Sanggil Kang, Kyungro Yoon,A Novel Approach in Sports Image

Classification, Lecture Notes in Computer Science (Proc. of the International Conference on Intelligent Computing ICIC 2006), August 2006.

l Wonil Kim, Sangyoon Oh, Sanggil Kang, Dongkyun Kim,Multi-module Image Classification System, Lecture Notes in Artificial Intelligence (Proc. of the 7th International Conference on Flexible Query

Answering Systems FQAS 2006), June 2006.

l Sangyoon Oh, Mehmet S. Aktas, Geoffrey C. Fox, Marlon Pierce, Architecture for High-Performance

Web Service Communications Using an Information Service, World Scientific and Engineering Academy and Society Transactions on Information Science and Applications, May 2006.

l Geoffrey C. Fox, Mehmet S. Aktas, Galip Aydin, Hasan Bulut, Harshawardhan Gadgil, Sangyoon Oh, Shrideep Pallickara, Marlon E. Pierce, Ahmet Sayar, and Gang Zhai,Grids for Real Time Data

Applications, Lecture Notes in Computer Science (Proc. of the 6th International Conference on Parallel Processing and Applied Mathematics PPAM 2005), Poznan Poland, September 11-14 2005.

l Sangyoon Oh, Sangmi Lee Pallickara, Sunghoon Ko, Jai-Hoon Kim, Geoffrey Fox,Cost Model and

Adaptive Scheme for Publish/Subscribe Systems on Mobile Environments, Lecture Notes in Computer Science (Proc. of the 2nd International Workshop on Active and Programmable Grids Architectures and Components APGAC05), May 2005.

l Sangyoon Oh, Sangmi Lee Pallickara, Sunghoon Ko, Jai-Hoon Kim, Geoffrey Fox,Publish/Subscribe

Systems on Node and Link Error Prone Mobile Environments, Lecture Notes in Computer Science (Proc. of Wireless and Mobile Systems Workshop in ICCS 2005), May 2005.

Full list of publications (II)

l Wenjun Wu, Ahmet Uyar, Hasan Bulut, Sangyoon Oh, Geoffrey Fox,Grid Service Architecture for

Videoconferencing, to appear as chapter in book "Grid Computational Methods" Edited by M.P. Bekakos, G.A. Gravvanis and H.R. Arabnia.

l M. Aktas, G. Aydin, H. Bulut, H. Gagdil, G. Fox, M. Nacar, M. Pierce, A. Sayar and S. Oh, XML Metadata

Services and Application Usage Scenarios, Proc. of The IEEE 2nd International Conference on Semantics, Knowledge and Grid (SKG2006), Guilin China, Oct. 31 – Nov. 3, 2006

l Sangyoon Oh, Mehmet S. Aktas, Marlon Pierce, Geoffrey C. Fox, Optimizing Web Service Messaging

Performance Using a Context Store for Static Data, Invited paper for 5th WSEAS International

Conference on TELECOMMUNICATIONS and INFORMATICS (TELE-INFO '06), Istanbul, Turkey, May 27-29, 2006.

l Geoffrey C. Fox, Mehmet S. Aktas, Galip Aydin, Andrea Donnellan, Harshawardhan Gadgil, Robert Granat, Shrideep Pallickara, Jay Parker, Marlon E. Pierce, Sangyoon Oh, John Rundle, Ahmet Sayar, and Michael Scharber, Building Sensor Filter Grids: Information Architecture for the Data Deluge,

Proc. of The IEEE International Conference on Semantics, Knowledge and Grid (SKG2005), Beijing China November 27-29 2005.

l Sangyoon Oh, Hasan Bulut, Ahmet Uyar, Wenjun Wu, Geoffrey C. Fox, Optimized Communication

using the SOAP Infoset For Mobile Multimedia Collaboration Applications, Proc. of the IEEE 2005 International Symposium on Collaborative Technologies and Systems (CTS 2005), St. Louis, Missouri, USA, May. 2005.

l Sangyoon Oh, Geoffrey C. Fox , Sunghoon Ko, GMSME: An Architecture for Heterogeneous

Collaboration with Mobile Devices, Proc. of the Fifth IEEE/IFIP International Conference on Mobile and Wireless Communications Networks (MWCN 2003), Singapore, October, 2003

Full list of publications (III)

l Geoffrey Fox, Sunghoon Ko, Kangseok Kim, Sangmi Lee, and Sangyoon Oh, Universal Accessible

Collaboration Frameworks for Ubiquitous Computing Environments,Proc. of International Conference in Ubiquitous Computing (ICUC 2003) in Seoul, Korea, October 2003

l Sangmi Lee, Sunghoon Ko, Geoffrey Fox, Kangseok Kim, and Sangyoon Oh, A Web Service

Approach to Universal Accessibility in Collaboration Services, Proc. of the 1st International Conference on Web Services (ICWS ’03), Las Vegas, USA, June 2003.

l Geoffrey Fox, Hasan Bulut, Kangseok Kim, Sung-Hoon Ko, Sangmi Lee, Sangyoon Oh, Shrideep Pallickara, Xiaohong Qiu, Ahmet Uyar, Minjun Wang, Wenjun Wu, Collaborative Web Services and Peer-to-Peer Grids,Proc. of the 2003 International Symposium on Collaborative Technologies and Systems (CTS 2003), Orlando, Florida, USA, Jan. 2003.

l Hasan Bulut, Geoffrey Fox, Dennis Gannon, Kangseok Kim, Sung-Hoon Ko, Sangmi Lee,Sangyoon Oh, Xi Rao, Shrideep Pallickara, Quinlin Pei, Marlon Pierce, Aleksander Slominski, Ahmet Uyar, Wenjun Wu, Choonhan Youn, An Architecture for e-Science and its Implications, Proc. of the 2002 International Symposium on Performance Evaluation of Computer and Telecommunication Systems (SPECTS 2002), San Diego, CA, USA, July 2002.

l Geoffrey C. Fox, Sunghoon Ko, Kangseok Kim,Sangyoon Oh and Sangmi Lee,Integration of