Web Service Architecture for Mobile Computing

1. Web Service Architecture for Mobile Computing Sangyoon Oh Department of Computer Science Indiana University Sangyoon Oh

2. Outline • Motivation • Research Issues • Our approach: HandHeld Flexible Representation Architecture • Performance Evaluation • Conclusion • Future work Sangyoon Oh

3. Motivation and Research Problem

4. 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

5. Important Obstacles in Integrating Web Services and Mobile Computing

6. 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

7. 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

8. <root><tag>one</tag><tag>two</tag><anotherTag>one</anotherTag><root><tag>one</tag><tag>two</tag><anotherTag>one</anotherTag> </root> {0}<root>{1}<tag>{0}one[1]<>{1}two{2}<anotherTag>[0] Fast Infoset: Example • No end tags • Indexing repeated string • Indexing qualified names Sangyoon Oh

9. Motivation • Performance has many aspects • XML parsing and transmission overhead often can not be afforded • A lot of research on message representation (e.g. binary XML) but not on the overall system framework • overcome or bypass possible performance overheads required to support optimizing messages • Security can be important and impact performance Sangyoon Oh

10. 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

11. Our approach: HandHeld Flexible Representation Architecture

12. Conventional Web Service Communication Model in Mobile Computing Sangyoon Oh

13. Our Approach: HHFR

14. Three Key Design Features • Distinguishes between message semantics and syntax • Using data description language e.g. Data Format Description Language (DFDL) style Simple_DFDL • Exchange messages in a streaming style • 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

15. 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

16. 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 ) • Use a data description file as a sample instance of messages in the stream Sangyoon Oh

17. Simple_DFDLand 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

18. Example:Simple_DFDL document <xs:element name="HHFR"> <xs:complexType> <xs:element name=“Float1" type=“float"/> <xs:element name=“Float2" type=“float"/> </xs:complexType> </xs:element>

19. 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

20. Negotiation Process • Use conventional SOAP message • Negotiate • HHFR-Capability • A preferred representation • Characteristics of Stream • QoS issues (e.g. reliability, security)

21. 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

22. 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

23. Normal Runtime Scenario • A HHFR-capable endpoint sends a negotiation request to intended service endpoint over SOAP. • Send an input data description • Service endpoint sends an output data description • Two endpoints exchange message in stream fashion • 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

24. Summary • Bandwidth problems in limited wireless connection • Optimized message representation • Reducing message size using Context-store • 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 • Transport level message streaming • Intermittent Wireless Connection • Context-store automates semantically persistent recovery Sangyoon Oh

25. Performance and Analysis

26. 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

27. Connection Setup Sangyoon Oh

28. Machine Configuration

29. 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

30. Performance Model and Measurements • Chhfr = nthhfr + Oa + Ob • Csoap = ntsoap • Breakeven point: nbe thhfr + Oa + Ob = nbe tsoap Oa(WS) is roughly 20 milliseconds Oa : overhead for accessing the Context-store Service Ob : overhead for negotiation

31. String Concatenation • Measure the total stream time i.e. summation of RTT • Independent variables • Number of messages per stream • Size of the message Sangyoon Oh

32. Floating Point Number Addition • Large Slope of SOAP • high latency of the HTTP based communication • SOAP parsing/ serialization overhead • There exist in non-zero locations breakeven point Sangyoon Oh

33. Performance saving by using Context-store Summary of the Round Trip Time (TRTT) • 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 Sangyoon Oh

34. 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 data-binding and HTTP request/response • Tstream: length of stream in seconds Sangyoon Oh

35. Summary of Ttime-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 Sangyoon Oh

36. Sangyoon Oh

37. 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

38. Conclusionsand Future Work

39. 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

40. Future work • Streaming channel integrated with a Web Service Container. • Provide a plug-in API for filter implementation • Integration with fully developed DFDL • Support more message type • Secure Message stream using negotiation process • Bouncy Castle lightweight cryptography package • WS-Policy specifying the default strategy • Read from Context-store or negotiation message • Relevance to non mobile (conventional ) case Sangyoon Oh

41. 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

42. 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

43. 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

44. 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. ofInternational 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 Hand-Held Devices into Collaborative Environments, Proc. the 1st International Workshop on Wired/Wireless Internet Communications (WWIC 2002), Las Vegas, NV, USA, April 2002. Sangyoon Oh