Transcript Introduction - Department of Computer Science and Engineering

Second semester FYP Presentation 2001~2002
LYU0101
Wireless Digital Information
System
Supervisor Prof. Michael Lyu
Yeung Kam Wah
Lam Yee Gordon
Overview
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Introduction
Design Direction
System Architecture
Client Implementation
Server Implementation
Work Done
Introduction
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PDA become more popular
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High Bandwidth Wireless Technology
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Computation power and Memory is
increasing
BlueTooth, Wireless LAN
3G
Demand for provide content to PDA
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Provide location related information
Wireless Digital Information System
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To build a generic system that allow
company provide their content to user
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Support different application
Support multimedia content
Same client program for different server
Search function
Wireless Digital Information System
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Usage
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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
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What’s our goal? (in previous slide)
Main Issues we need to concern:
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Data (format, storage, types)
Search Engine (vector,probabilistic model,
indexing, ranking, relevance feedback)
Platform (hand-held device)
Concern 1:Data
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Use XML as the primary data format
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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
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Use XSL to change XML into information
changes in module or client platform will not
affect the data
Concern 1:Data
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Storing XML in Database
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Database provides us many useful services
Other
concurrency
control
Security
recoverability
of data
Data
Management
and
Integration
Concern 1:Data
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Conversion between XML and Database
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Common Method:
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Break down XML file into tree nodes and remember its
children's node
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Need to have different schema
Need to make use of DTD
Our Method:
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Break down XML file into tree nodes and remember the
parent node.
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Only need one schema: (parent id, node id, type, data)
Concern 1:Data
<!ELEMENT author ( name, address )>
<!ATTLIST author id ID REQUIRED>
<!ELEMENT name(firstname?, lastname)>
<!ELEMENT firstname(PCDATA)>
<!ELEMENT lastname(PCDATA)>
<!ELEMENT address ANY >
A DTD definition
Visualization of DTD in Tree
Concern 2: Searching
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Use Vector Model
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assign weight to index terms in queries
and in XML file (from tf factor, termfrequency 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
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A full inverted index is built.
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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
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Problem: client may need only ten
search results at a time, I can’t send all
the result to PDA client at a time !!!
Solution: NN-search Methods (R-tree,
SS-tree, SR-tree, X-tree, MVP-tree, Atree, VA-file)
We choose VA-file
Concern 2: Searching
VP-tree
A-tree
Concern 2: Searching
VA-file
Concern 2: Searching
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Reason for choosing VA-file:
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performs much better than the others in
high-dimension space(as number of index
term may be over thousand)
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IO page, number of Vector calculation, CPU
time in search
CPU time on construction
Concern 3: Client Platform
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We choose Pocket PC as our client
platform
Reason:
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Pocket PC have better support in
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Internet
Multi-Media
Performance
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processing power of Pocket PC is higher than
Palm OS nowadays
System Architecture
System Architecture
Pre-Process
System
XML
Database
Index
Search Engine
request
PDA client
Network
TCP/IP, HTTP
XML/HTML
Media server
server
Query & Result
XLS
System Architecture
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Server side
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XML Data is processed and stored in the
database
A set of XSL is used to format the output
Client side
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Display information
Send user requests to server
Server Side
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Four main components at Server Side
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XML Pre-processor
Search Engine
XSL transformer
TCP Server that Communicate with PDA client
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incoming: Keyword search, Map search result, XSL and
XML set
outgoing: HTML, Video xml definition (probably a very
simple SMIL), Map xml definition
Web server (images)
MMS server (videos)
XML Pre-processor
XML Data
Struture + Text
Strutural
parsing
tuples
Text
Accents,
spacing, etc
Lexical
Analysis
Building Full
Inverted index
Vector and
VA-file Builder
Vectors and
VA-file
Relational Database
The PDA Client
server
PDA Client
Control Component
Main Window
Image Window
Video Window
The PDA Client
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Main Window
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HTML Viewer
Supported by system
provided DLL
Interface for
information
displaying
User event will pass
to control component
to handle
The PDA Client
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Image Window
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Using to display
image
Points highlight
feature
Using as query input
interface, user can
select a rectangular
area as query input
The PDA Client
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Video/Audio window
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Supported by system
provided COM Object
Display video to user
The PDA Client
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Why using HTML viewer as main interface
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Provide feasibility to different servers using their
own interface
HTML is widely used and designed for display
information.
Why using system provide library
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Simplify the program and slim the program size
These component is optimized
Work Done and Possible
Extension
Work Done
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2001 July ~ Aug
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Study different wireless network
Study different PDA platform
Build a trial application on Pocket PC
2001 Sep ~ Dec
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Design the application and system
architecture
Build the Pocket PC client
Work Done
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2002 Jan ~ April
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Study the searching algorithm
Build the server
Continue implement the Pocket PC client