Web Service Architecture
for Mobile Computing
Sangyoon Oh
Department of Computer Science
Indiana University
Sangyoon Oh
1
Outline



Motivation
Research Issues
Our approach:
HandHeld Flexible Representation Architecture



Performance Evaluation
Conclusion
Future work
Sangyoon Oh
2
Motivation and Research Problem
3
Web Service and Mobile Computing

Web Service inter-relates distributed functionalities
(i.e. services) in an elegant and technology-neutral
manner.

Mobile devices with wireless connections have
become a vital part of people’s everyday life.


Play audio/video, Access Web, Multiplayer gaming through
wireless connection, participate in collaboration session.
3G cellular network (downloading up to 500kbps), 802.11b/g
(54Mbps), or WiBro / WiMAX (practical bandwidth up to 2Mbps)
Sangyoon Oh
4
Important Obstacles
in Integrating Web Services and Mobile Computing
2. Processing (i.e. Parsing and
Serializing) XML message
(e.g. Increased the Size of Messages)
SOAP
SOAP
Mobile
Station
1. Bandwidth
Problem
SOAP
Database
Base
Station
Internet
SOAP
3. HTTP Request/
Response mechanism
SOAP
File Server
Computing
5
Some Current Approaches

Compressing XML Document




gzip, XMill
Able to reduce a document size
However, the additional layer required to
compress and to decompress add a significant
overheads
Attaching binary data to SOAP message

MTOM/XOP: MIME attachment


JPG, MP3: standardized format
DIME: Wrapping binary data
Sangyoon Oh
6
Fast Infoset

Specifies a representation of
an instance of the XML
Infoset using binary encoding.



XML Infoset Specification is
used to refer information in well
formed XML.
Doesn’t tied up with XML API
(e.g. DOM, SAX)
Use ASN. 1. for binary
encoding
Sangyoon Oh
7
Fast Infoset: Example
•No end tags
•Indexing repeated string
•Indexing qualified names
<root>
<tag>one</tag>
<tag>two</tag>
<anotherTag>one</anotherTag>
</root>
Local Name
{0}<root>
{1}<tag>{0}one
[1]<>{1}two
{2}<anotherTag>[0]
Content
0
root
0
one
1
tag
1
two
2
anotherTag
2
Sangyoon Oh
8
Motivation

Performance has many aspects


A lot of research on message representation (e.g.
binary XML) but not on the overall system
framework


XML parsing and transmission overhead often can not be
afforded
overcome or bypass possible performance overheads
required to support optimizing messages
Security can be important and impact performance
Sangyoon Oh
9
Research Issues




Architecture of Interaction of mobile client
and Web Service.
A negotiation architecture that allows protocol
independent solutions
A data description language that allows
conversion between multiple representations
Adopt database semantics to reduce
message size and store negotiated
characteristics
Sangyoon Oh
10
Our approach:
HandHeld Flexible
Representation Architecture
11
Conventional Web Service Communication
Model in Mobile Computing
Service Provider
SOAP
Parser
SOAP Engine
SOAP
Sangyoon Oh
SOAP
Parser
Service Client
12
Message Stream
Simple_DFDL Doc.
Static Metadata
Service Client
(HHFR-Capable)
HHFR
Architecture
Negotiation
(SOAP)
Filter
Filter
HHFR
Architecture
Store and retrieve
static meta-data
SOAP
Parser
SOAP Engine
Service Provider
(HHFR-Capable)
SOAP
Parser
Our Approach: HHFR
Store and retrieve
static meta-data
Stream Characteristcs
Context-Store
(WS-Context Compliant
Information Service)
13
Three Key Design Features
1.
Distinguishes between message semantics and syntax

Using data description language e.g. Data Format Description
Language (DFDL) style Simple_DFDL
2. Exchange messages in a streaming style

3.
Use streaming at protocol and semantic level
Using Context-store to hold static data

Unchanging/redundant SOAP message parts

Simple_DFDL as a data representation

Negotiated stream characters
Sangyoon Oh
14
Messaging Style


Producer and Consumer of data have access
to its Schema (Static data binding)
Stream -- set of related messages



Messages in the stream  the same structure
and same data type
Mobile clients (e.g. PDAs or smart phones)
access to Grid job
Message size is tend to be small (e.g. in
mobile computing)
Sangyoon Oh
15
Distinguishing
XML Syntax and Semantics
Our XML data model is defined by XML
Infoset specification.
Our approach


Distinguish semantic (message content) and
syntax

e.g. <year>2006</year>
Its syntax and value, 2006



To define the XML syntax
Use a data description language (Simple_DFDL )
b) Use a data description file as a sample instance of messages
in the stream
a)
Sangyoon Oh
16
Simple_DFDL
and Processing Module


Mapping data between representations
Processing architecture




Simple_DFDL describes data format
Processor (DSParser) builds the HHFR Data model
Filter converts data from and to the preferred
representation format
A follow-on project is to integrate HHFR with fully
developed DFDL

HHFR starts with Simple_DFDL and will move to DFDL.
Sangyoon Oh
17
Example:
Simple_DFDL document
<xs:element name="HHFR">
<xs:complexType>
<xs:element name=“Float1" type=“float"/>
<xs:element name=“Float2" type=“float"/>
</xs:complexType>
DSParser
</xs:element>
(Simple_DFDL
Processor)
SOAP Negotiation
Message
Simple_DFDL
Document
HHFR Data Model
Data
Streamer
(i.e. Filter)
Data in the preferred
representation on-the-wire
Message Handling

Filters
 Convert representations


XML-to-binary, binary-to-language specific data model
Handler for Headers
 Conventional Handler Approach: Convert back to SOAP
 Make a handler understand alternative representation

e.g. WS-RM handler could be taught alternative representation
Handler
...
Handler
Header
Filter
Body
Processor
Body
19
Negotiation Process


Use conventional SOAP message
Negotiate




HHFR-Capability
A preferred representation
Characteristics of Stream
QoS issues (e.g. reliability, security)
Web
Service
Client
Web
Serrice
Client
Negotiation
Request
Negotiation
Request
Negotiation
Response
(False or Error)
Negotiation
Response
(True)
create
SOAP
Message
Exchange
create
Message
Stream
20
Streaming Related Issues

Transport:

HTTP transport could be a performance
bottleneck  well known fact



TCP/IP connection setup overhead, Request/Response.
Persistent Connection may be not guaranteed in Cellular
environment
Representation:

Using Context-store saving of redundant /
unchanging data
Sangyoon Oh
21
Context-store

Strategy: archiving static meta-data and
negotiated information

Any WS enabled Database could be used

Guarantees semantically persistent recovery

WS-Context specification

Use URI to store and retrieve

Fault Tolerant High Performance Information
Service (FTHPIS) of CGL
Sangyoon Oh
22
Normal Runtime Scenario
A HHFR-capable endpoint sends a negotiation request
to intended service endpoint over SOAP.
1.
a)
Send an input data description
b)
Service endpoint sends an output data description
Two endpoints exchange message in stream fashion
2.

3.
Messages in the stream are in the form of negotiated
representations
The redundant / unchanging static metadata and
negotiation details are stored in Context-store
Sangyoon Oh
23
Summary

Bandwidth problems in limited wireless connection



Parsing & Serializing overhead to less powered
processor in mobile device



Avoiding conventional SOAP processing
Simple_DFDL & Filters process message in efficient way.
HTTP request/response in high latency wireless
connection


Optimized message representation
Reducing message size using Context-store
Transport level message streaming
Intermittent Wireless Connection

Context-store automates semantically persistent recovery
Sangyoon Oh
24
Performance and Analysis
25
Performance Evaluation

Experiments are intended to show





Performance comparisons between a
conventional SOAP based client and a HHFR
based client
Savings and gains from Context-store
Analyzed optimal scalability using Context-store
Service clients are running on Treo600
Experiments run through actual 2G cellular
connections
Sangyoon Oh
26
Connection Setup
Service A
(String Concatenation)
Cellular
Gateway
Internet
Cellular Tower
Service B
(Floating Point Number Addition)
Wired
Wireless
Treo
600
Sangyoon Oh
27
Machine Configuration
Service Provider: Grid Farm 8
Processor
Intel® Xeon™ CPU (2.40GHz)
RAM
2GB total
Network Bandwidth
100Mbps
OS
GNU/Linux (kernel release 2.4.22)
Java Version
Java 2 platform, Standard Edition (1.5.0-06)
SOAP Engine
Axis 1.2 (in Tomcat 5.5.8)
Service Client: Treo 600
Processor
RAM
Network Bandwidth
OS
Java Version
ARM (144MHz)
32MB total, 24MB user available
14.4Kbps (Sprint PCS Vision)
Palm 5.2.1.H
Java 2 platform, Micro Edition
CLDC 1.1 and MIDP 2.0
28
System Parameters






thhfr : time per message in a HHFR performance model
tsoap : time per message in a conventional SOAP performance model
Oa : overhead for accessing the Context-store Service
Ob : overhead for negotiation
Chhfr : total time for finishing stream of the HHFR
Csoap : total time for finishing stream of the conventional SOAP framework
Context-store
(Information Service)
Oa
Negotiation through SOAP
Service Provider
(Endpoint A)
Ob
thhfr
Stream Communication
Channel of HHFR
Mobile Client
(Endpoint B)
29
Performance Model and Measurements



Chhfr = nthhfr + Oa + Ob
Csoap = ntsoap
Oa : overhead for accessing the
Context-store Service
Ob : overhead for negotiation
Breakeven point:
nbe thhfr + Oa + Ob = nbe tsoap
Average±error (sec) Stddev (sec)
Context-store Access (Oa)
4.127±0.042
0.516
Negotiation (Ob)
5.133±0.036
0.825
Oa(WS) is roughly 20 milliseconds
30


Measure the total
stream time i.e.
summation of RTT
Independent
variables
 Number of
messages per
stream
 Size of the
message
Time for Finishing Message Stream (sec)
String Concatenation
140
120
HHFR: 16 String Per Message
SOAP: 16 String Per Message
100
80
60
40
20
0
0
5
10
15
20
25
30
Number Of Messages Per Stream
Sangyoon Oh
35
31


Large Slope of
SOAP
1. high latency of
the HTTP
based
communication
2. SOAP parsing/
serialization
overhead
There exist in
non-zero
locations
breakeven point
Time for Finishing Message Stream (sec)
Floating Point Number Addition
140
120
HHFR: 16 Floats Per Message
SOAP: 16 Floats Per Message
100
80
60
40
20
0
0
5
10
15
20
25
30
Number Of Messages Per Stream
Sangyoon Oh
35
32
Performance
saving by using Context-store

Experiments ran over HHFR



Optimized message exchanged over HHFR after saving
redundant/unchanging parts to the Context-store
We use WS-Addressing message for the experiment.
Save on average 83% of message size, 41% of transit time
Summary of the Round Trip Time (TRTT)
Message Size
Full SOAP Message
Optimized Message
Ave.±error
Stddev
Ave.±error
Stddev
Medium: 513byte (sec)
2.76±0.034
0.187
1.75±0.040
0.217
Large: 2.61KB (sec)
5.20±0.158
0.867
2.81±0.098
0.538
Sangyoon Oh
33
System Parameters

N: the maximum number of stream supported by
one server

Twsctx: time consumed to process (setContext) an
operation

Ttime-in-server: time consumed in Axis server

Taxis-overhead: time consumed to process Axis databinding and HTTP request/response

Tstream: length of stream in seconds
Sangyoon Oh
34
Summary of Ttime-in-server measurements
Ttime-in-server = Twsctx + Taxis-overhead
Twsctx =< 1 milliseconds
300
Axis 1.2 Beta3 is used
250
Time (msec)
Data binding overhead
at Web Service Container
is the dominant factor to
message processing
T(time-in-server)
200
150
100
50
0
1.2
Sangyoon Oh
1.4
1.6
1.8
Size of Context (KB)
2
35
2.2
300
T(WSCTX)
T(Data-Binding)
T(SOAP-Sending-Receiving)
Time (msec)
250
200
150
100
50
0
1.3
1.4
1.5
1.6
Sangyoon 1.7
Oh
1.8
1.9
Size of Context (KB)
2
2.1
36
Allowed Maximum Number of Stream
by Server
N: the maximum number of stream supported by one server
3N/Tstream ≈ 1 / Ttime-in-server (N/T stream starts and N/T stream ends)
N ≈ Tstream / (3 * Ttime-in-server)
e.g. Tstream = 600 (sec),
Ttime-in-server = 0.035 (when the context-size is 1.2 Kbyte)
N ≈ 600 / {3 * 0.035}
N ≈ 5700
Sangyoon Oh
37
Conclusions
and Future Work
38
Summary of Contributions


Design and implement an overall system framework architecture:
The HHFR Architecture provides

A mechanism to negotiate the characteristics of a stream

A streaming communication channel

Simple_DFDL which distinguishes the semantics from the
representation of message content

An interface to Information service (Context-store)

A semantically persistent recovery framework
Detailed performance evaluation

Benchmark applications, approach to use a Context-store
Sangyoon Oh
39
Future work



Streaming channel integrated with a Web Service
Container.
Provide a plug-in API for filter implementation
Integration with fully developed DFDL


Secure Message stream using negotiation process


Bouncy Castle lightweight cryptography package
WS-Policy specifying the default strategy


Support more message type
Read from Context-store or negotiation message
Relevance to non mobile (conventional ) case
Sangyoon Oh
40
Related publications

Sangyoon Oh and Geoffrey Fox, “Optimizing Web Service Messaging
Performance in Mobile Computing,” Future Generation Computer Systems
Journal, Revision being processed.

M. Aktas, S. Oh, G. Fox, and M. Pierce, “XML Metadata Service” Proc. of the
IEEE 2nd International Conference on Semantics, Knowledge and Grid
(SKG2006), Nov. 2006

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

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.
Sangyoon Oh
41
Full list of publications (I)







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.
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.
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.
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.
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.
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.
G. Fox, S Ko, M Pierce, O Balsoy, J Kim, S Lee, K Kim, S Oh, X Rao, M Varank, H Bulut, G Gunduz, X
Qui, S Pallickara, A Uyar, Grid Service for Earthquake Science, Concurrency and Computation:
Practice and Experience in ACES Special Issue, 14, 371-393, October 2002.
Sangyoon Oh
42
Full list of publications (II)






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.
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
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.
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.
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.
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
Sangyoon Oh
43
Full list of publications (III)





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
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.
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.
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.
Geoffrey C. Fox, Sunghoon Ko, Kangseok Kim, Sangyoon Oh and Sangmi Lee, Integration of HandHeld Devices into Collaborative Environments, Proc. the 1st International Workshop on
Wired/Wireless Internet Communications (WWIC 2002), Las Vegas, NV, USA, April 2002.
Sangyoon Oh
44
Descargar

Slide 1