The procedure stops when the result of a region query

Info icon This preview shows pages 2–5. Sign up to view the full content.

points than the previous query. The procedure stops when the result of a region query is non-empty. The distance from P to each point within this region is calculated and the set of points at the smallest distance is reported. 25.4 Suppose you want to store line segments in an R-tree. If a line segment is not parallel to the axes, the bounding box for it can be large, containing a large empty area. Describe the effect on performance of having large bounding boxes on queries that ask for line segments intersecting a given region. Briefly describe atechnique toimprove performance for suchqueries and give an example of its benefit. Hint: You can divide segments into smaller pieces. Answer: Large bounding boxes tend to overlap even where the region of overlap does not contain any information. The following figure: R shows a region R within which we have to locate a segment. Note that even though none of the four segments lies in R , due to the large bounding boxes, we have to check each of the four bounding boxes to confirm this. A significant improvement is observed in the follwoing figure:
Image of page 2

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

Practice Exercises 3 R where each segment is split into multiple pieces, each with its own bounding box. In the second case, the box R is not part of the boxes indexed by the R-tree. In general, dividing a segment into smaller pieces causes the bounding boxes to be smaller and less wasteful of area. 25.5 Give a recursive procedure to efficiently compute the spatial join of two relations with R-tree indices. (Hint: Use bounding boxes to check if leaf entries under a pair of internal nodes may intersect.) Answer: Following is a recursive procedure for computing spatial join of two R-trees. SpJoin (node n 1 , node n 2 ) begin if (the bounding boxes of n 1 and n 2 do not intersect) return ; if (both n 1 and n 2 are leaves) output all pairs of entries ( e 1 , e 2 ) such that e 1 n 1 and e 2 n 2 , and e 1 and e 2 overlap; if ( n 1 is not a leaf) NS 1 = set of children of n 1 ; else NS 1 = { n 1 } ; if ( n 1 is not a leaf) NS 1 = set of children of n 1 ; else NS 1 = { n 1 } ; for each ns 1 in NS 1 and ns 2 in NS 2 ; SpJoin( ns 1 , ns 2 ); end 25.6 Describe how the ideas behind the RAID organization (Section 10.3) can be used in a broadcast-data environment, where there may occasionally be noise that prevents reception of part of the data being transmitted.
Image of page 3
4 Chapter 25 Advanced Data Types and New Applications Answer: The concepts of RAID can be used to improve reliability of the broadcast of data over wireless systems. Each block of data that is
Image of page 4

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

Image of page 5
This is the end of the preview. Sign up to access the rest of the document.
  • Spring '13
  • Dr.Khansari
  • access time, Seek time, Rotational delay, advanced data types

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern