Sonyfe25cp的玩具

8.13 台北科技大学 刘传铭

###Skyline Query

Skyline Query是Locationbased service中的一种很重要的查询

LBS 主要包含以下：

• Point query
• Range query
• Nearest neighbor
• Shortest path query
• Skyline query

Skyline Example

Which hotel is nearest and cheapest one ?

The skyeline query finds the data items that meet the given conditions as possible.

###Data broadcasting

Data broadcasting provides an effective way to disseminate information to a large amount of mobile clients

• Wireless mobile network is asymmetric
• Server broadcasts data periodically and the clients tune into the broadcast channel to receive data
• Nuber of clients is oftern higer thant servers
• Energy is a scarce resource at the mobile unit//如何省电

####Measuring Performance

• Latency
• Tuning time
  • Time spent listening to the broadcast
  • Controls power consumption
• Memory usage

Data have spatial and non-spatial attribute

R-tree is used to index spatial data.

MBR 最小边界矩形

利用坐标X,Y，价格 构成3维空间，然后建立R* tree，寻找Skyline

###Uncertain Data Streams

• Precise data
  • Data without ambiguity
  • e.g. Student’s score
• Uncertain data
  • Data having error, incompleteness or ambiguity

####Uncertain Data

• Given a d-dimensional uncertain data set U, an ucertain data object X is a probability distribution over d-dimesion space

####Simulated Experiments

• EPSU
• CL
• CLG