Download presentation
Presentation is loading. Please wait.
Published byReynold Fisher Modified over 9 years ago
1
Graphics Application Lab Myoung-Ah Kang, Sylvie Servigne,Ki-Joune Li, Robert Laurini CIKM’ 99 Kim Hyong-Jun, Yoon Tai-Jin GA Lab. Indexing Field Values in Field Oriented Systems : Interval Quadtree
2
Graphics Application Lab Motivation 2 Query based on given position Query based on given field value
3
Graphics Application Lab Notation for field Representation Field Representation 3 Digital Elevation Model (DEM) Triangulated Irregular Network (TIN)
4
Graphics Application Lab Notation for Field Queries Field Query Variables oSpatial variable : S oValue variable : V Query Representation 4 Q1 : f 1 (S) = V (Find field value on a given area S.) Q2 : f 1 (V) = S (Find region with a given field value V.)
5
Graphics Application Lab Subfield & Field Query Processing Subfield 5 F i = (A i, V min,i, V max,i ) Field value Space(x,y)
6
Graphics Application Lab Subfield & Field Query Processing Quadtree 6 54,62 49,5946,56 55,65 64,74 68,78 59,68 64,70 73,80 60,66 65,75 58,6964,73 1(46,80) 2(58,75) 3(73,80)4(64,70) 5(46,78) 6(60,66)7(65,75)8(58,69)9(64,73)10(68,78)11(64,74)12(59,68) 13(54,62)14(55,65)15(49,59)16(46,56)
7
Graphics Application Lab Field Query Processing Strategy Step 1 (filtering step) : find all subfields whose interval overlaps with [50,60] 7 54,62 49,5946,56 55,65 64,74 68,78 59,68 64,70 73,80 60,66 65,75 58,6964,73 Step 2 (refinement step) : retrieve all field objects in the selected subfields by step 1 Step 3 (estimation step) : estimate the region where value is between [50,60] based on the low level representation method of field
8
Graphics Application Lab Pointer-based Quadtree 8 1(46,80) 2(58,75) 3(73,80)4(64,70) 5(46,78) 6(60,66)7(65,75)8(58,69)9(64,73)10(68,78)11(64,74)12(59,68) 13(54,62)14(55,65)15(49,59)16(46,56) Procedure Field value indexing By Pointer Quadtree Input: P(root node of quadtree) I (given field values) Output: B (set of field objects) A = {P}. B = {}. while A is not empty, m = delete a node in A. if A is non-leaf & interval(m) overlaps with I, then insert four child nodes into A. if m is leaf node & interval(m) overlaps with I, then insert the field objects of m into B End while End procedure
9
Graphics Application Lab Pointer Quadtree Weak points Relatively a large amount of storage space and it leads to frequent disk accesses when following pointers scattered on several branches of quadtree, we must traverse many paths in the quadtree oRe organized using a tree structure in form of B-tree or one of its variations 9
10
Graphics Application Lab Interval Quadtree Transformation invervals of field values 10 Leaf node = (S id, N id, Size,V min, V max, D) Subfield 6 5060 Subfield 5 Subfield 3 Subfield 4 Subfield 2 Subfield 1 Field value Original Field value Dimension max min 3 6 2 4 1 5 50 60 Transformed Space
11
Graphics Application Lab Implementaion and Performance 11 Relative Interval size of threshold Number of subfields Height of R*-tree Filtering time(ms) Refinement time(ms) 0.0552204414596 0.11572433669 0.238893776 0.3207733109 0.4142332113 0.589821139 0.640621149 0.73720.1162 0.81910.0172 0.91310.0172 0.95410.01170 Comparison betwwen Interval Quadtree with R*-tree and Linear scanning Some variables according to the relative interval size of threshold
12
Graphics Application Lab Comparison of proposed method 12 Camparison of proposed indexing structures Constructed R*-tree with 3-d rectangles of subfields obtained
13
Graphics Application Lab Conclusion Divide a field into several subfileds oDifference between the max value and min value oUse Quadtree for division Proposed and evaluated two indexing structures oPointer-based Quadtree oInterval Quadtree oR*-tree for benchmark 13
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.