Wireless DI System: Design and Implementation for PDA Users

1. Second semester FYPPresentation 2001~2002 LYU0101 Wireless Digital Information System Supervisor Prof. Michael Lyu Yeung Kam Wah Lam Yee Gordon

2. Overview • Introduction • Design Direction • System Architecture • Work Done • Possible Improvement

3. Introduction • PDA become more popular • Computation power and Memory is increasing • High Bandwidth Wireless Technology • BlueTooth, Wireless LAN • 3G • Demand for provide content to PDA • Provide location related information

4. Wireless Digital Information System • To build a generic system that allow company provide their content to user • Support different application • Single client for different server • Search function • Support multimedia content

5. Wireless Digital Information System • Usage • Shopping guild in a Shopping Mall • Information search in an Exhibition • Showing vacancy in a Car Park • Digital video Library client

6. Design Direction

7. Design Direction • What’s our goal? (in previous slide) • Main Issues we need to concern: • Data (format, storage, types) • Search Engine (vector,probabilistic model, indexing, ranking, relevance feedback) • Platform (hand-held device)

8. Concern 1:Data • Use XML as the primary data format • To give our user a standard, feasible and extensible way to design the data structure • separate the concern on the data and presentation of information • Use XSL to change XML into information • changes in module or client platform will not affect the data

9. Concern 1:Data • Storing XML in Database • Database provides us many useful services, e.g. building different kinds of indexing on data, concurrency control, recoverability of data, etc. • Break down XML file into tree nodes and store as tuples (parent id, node id, type, data) • easy for locate and update the data in XML • reform the XML on need

10. Concern 2: Searching • Use Vector Model • assign weight to index terms in queries and in XML file (from tf factor, term-frequency and idf factor, inverse document frequency) • compute degree of similarity between each XML file and user query • give ordering of XML file

11. Concern 2: Searching • A full inverted index is built. • have a better ranking, e.g. search for “林怡”, I prefer to have “林怡”in search result, rather than “林保怡”. • can help in searching a whole phase.

12. Concern 2: Searching • Problem: client may need only ten search results at a time, I can’t send all the result to PDA client at a time !!! (in decreasing of the similarity, just like have different result page in google) • NN-search Methods (R-tree, SS-tree, SR-tree, X-tree, MVP-tree, A-tree, VA-file) • We choose VA-file

13. Concern 2: Searching • Reason for choosing VA-file: • performs much better than the others in high-dimension space(as number of index term may be over thousand) • IO page, number of Vector calculation, CPU time in search • CPU time on construction • Characteristics of VA-file: • no MBRs, no Tree, use approximation linear search, just build a small filter file

14. Concern 3: Client Platform • We choose Pocket PC as our client platform • Reason: • Pocket PC have better support in • Internet • Multi-Media • Performance • processing power of Pocket PC is higher than Palm OS nowadays

15. System Architecture

16. System Architecture

17. System Architecture • Server side • XML Data is processed and stored in the database • A set of XSL is used to format the output • Client side • Displace information • Send user request to server

18. Server Side • Four main components at Server Side • XML Pre-processor • Search Engine • XSL transformer • TCP Server that Communicate with PDA client • incoming: Keyword search, Map search result, <XSL,XML> • outgoing: HTML, Video xml definition (probably a very simple SMIL), Map xml definition • Web server (images) • MMS server (videos)

19. XML Pre-processor Vector and VA-file Builder Vectors and VA-file

20. The PDA Client • The four main components • Control component • Main window • Video window • Image window

21. The PDA Client • Main Window • HTML Viewer • Supported by system provided DLL • Interface for information displaying • User event will pass to control component to handle

22. The PDA Client • Video/Audio window • Supported by system provided COM Object • Display video to user • Image Window • Using to display image • Points highlight feature • Using as query input interface, user can select a rectangular area as query input

23. The PDA Client • Why using HTML viewer as main interface • Provide feasibility to different servers using their own interface • HTML is widely used and designed for display information. • Why using system provide components • Simplify the program and slim the program size • These component is optimized

24. Work Done and Possible Improvement

25. Work Done • 2001 July ~ Aug • Study different wireless network • Study different PDA platform • Build a trial application on Pocket PC • 2001 Sep ~ Dec • Design the application and system architecture • Build the Packet PC client

26. Work Done • 2002 Jan ~ April • Study the searching algorithm • Build the server • Continue implement the Pocket PC client

27. Possible Improvement • At Server Side: • relevance feedback (improvement on query) • caching (better performance) • At Client side: • enhancement on the Main window, Image window and Video window

28. Q & A Section