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INDEX
• Overview
• Issues in Mobile Databases
– Data management
– Transaction management
• Mobile Databases and Information
Retrieval
Mobile Database Systems
• Distributed system with mobile
connectivity
• Full database system capability
• Complete spatial mobility
• Wired and wireless communication
capability
Possible Applications
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Traffic control
Taxi dispatch
Emergencies services: police, medical, fire, …
Car navigation
Location-aware search and recommendation
Social applications: information / opinion
sharing and search among community
• Limited wireless bandwidth and
communication speed
• Limited power (battery life)
• Limited screen size for output
• Limited query capability for input
• Limited computing & storage capacity
• Less secure
• Anywhere: can physically move around
without affecting data availability
• Anytime: can store and retrieve any
data whenever mobile connection is
available
• Efficiency: can process mobile data
efficiently
• Effectiveness: can give users what they
really want (, and skip the less
relevant…)
• To build a ubiquitous information
processing system given the inherent
limitations of mobile devices and
wireless communications
• Data management
– Data caching
– Representation and storage of mobile data
– Data classification
• Transaction management
– Query processing
– Concurrency control
– Transaction and error recovery
• How to improve data availability to user
queries in mobile database systems?
– Data caching
• Results of previous queries are cached on mobile clients
• Query log can be further used in personalization and
recommendation
– Representation and storage of mobile data
• Spatial data management
• Indexing and retrieval schemes
– Data classification
• Location-dependent
• Location-independent
• Results of previous queries are cached
on mobile clients
– Cache size
– Cache freshness/update frequency
– Cache consistency
• Query log can be further used in
personalization and recommendation
– User preference learning
• keywords, categories, location
– Collaborative filtering for content
recommendation
Representation and storage of
mobile data
• Spatial data management
– Location information
– Data volume, update frequency, persistency
• Indexing and retrieval schemes
– High-dimensional feature space
– Structure for improving retrieval efficiency
• Location-dependent
– Location-based services
• E.g. nearby gas stations or restaurants within
1km, available paths to the park, …
– Database distribution or replication must
take location into consideration
• Distributed vs. centralized
• Location-independent
– Personal name, account information, plate
number, …
• Query processing
• Concurrency control
• Transaction and error recovery
• Query types
– Location dependent query
– Location aware query
– Location independent query
• A query whose result depends on the
geographical location of the query origin
– E.g.
• What are the 3 nearest gas stations or
restaurants?
• What is the shortest path to the park?
– GPS can facilitate this
• Outdoor only
• WLAN could cover most of the indoor locality
Location aware query
• A query whose context might be related
to locations
– E.g.
• Find out all the car plates passing through the
traffic light between 7:00-8:00pm
• Find out the current location of the bus on route
#212
• Find out the top 5 roads that have the most
traffic in Taipei (the slowest car speed)
Concurrency control
• Similar to the issues of concurrency
control in distributed systems
– Time synchronization
• Timestamps, clocks
– Latency in mobile queries
– Similar issues to cache consistency
• Size of query results
Transaction and error recovery
• Conventional transaction properties
– Atomicity
– Consistency
– Isolation
– Durability
• Too rigid for mobile database
– Flexibility can be introduced
Possible issues in mobile
transactions
• Transactions
– Wireless communication availability and
overhead
– Hard to manage locking and unlocking
operations
– Limited power
• Recovery
– Efficient logging and check pointing
– Log duplication
Other Concerns
• In mobile e-commerce, security in mobile
data and transactions are critical
– Less support in wireless security
• WEP, IEEE 802.11i
– Identity authentication
– Privacy issues of user location
Possible Challenges and Issues
• Indexing and storage of mobile data
• Efficient query processing and retrieval of
mobile data
• Content adaptation and information
presentation for small display
• Automatic summarization and personalization
of mobile data
• Scalable algorithms for large mobile databases
• Knowledge sharing among mobile peers
• Security and trusted retrieval of mobile data
• Location-based search for mobile devices
Mobile Databases and
Information Retrieval
• Mobile information retrieval
– Context awareness
– Content adaptation
Context Awareness
• Location information
• Built-in camera
• Social networks
Possible research topics related to
context awareness
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Location-based search
Spatial data mining
Query log mining
User profiling and recommendation
Knowledge sharing
Content Adaptation
• Small screens
• Less processing power
• Less memory and storage
Possible research topics related to
content adaptation
Automatic summarization
Information filtering
User personalization
Efficient indexing and retrieval of
mobile media
• Scalable algorithms
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