lyu0101 wireless digital information system lam yee gordon yeung kam wah supervisor prof. michael...

LYU0101

Wireless Digital Information System

Lam Yee Gordon Yeung Kam Wah

Supervisor Prof. Michael Lyu

Second semester FYP Presentation 2001~2002

Overview Introduction Design Direction System Architecture Work Done Possible Improvement

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

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

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

Design Direction

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)

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

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

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

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.

Concern 2: Searching Problem: client may need only ten searc

h 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

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

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

System Architecture

System Architecture

Database

XML

PDA clientNetwork

TCP/IP, HTTP

request

XLS

server Query & ResultXML/HTML

Media server

Index

Pre-ProcessSystem

Search Engine

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

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)

XML Pre-processor

XML Data Strutural

parsing Struture + Text

Relational Database

Accents,

spacing, etc

Lexical

Analysis

Text

Building Full

Inverted index

tuples

Vector andVA-file Builder

Vectors andVA-file

The PDA Client The four main components

Control component Main window Video window Image window

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

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

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

Work Done and Possible Improvement

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

Work Done 2002 Jan ~ April

Study the searching algorithm Build the server Continue implement the Pocket PC

client

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