Web Data Management (WDM): Exercise 2 (Submissions due to April 2)

Exercise 2 (Submissions due to April 2)

Textbook Exercise 2.7.1. In addition, draw the document of Figure 2.12 as
an XPath tree. Test your expressions using some XPath evaluator. A simple
command-line tool is given as a Java application xpathTest.
It can be used as follows, say, form a Linux command line:
```
  $ javac xpathTest.java
  $ java xpathTest --nodes '//text()/..' ex_2_7_1.xml
  NODE #1:
  <b di="7" id="3">bli <c/>
  <c>
  <e>bla</e>
  </c>
  </b>
  NODE #2:
  <e>bla</e>
  NODE #3:
  <d>bou</d>
```
Textbook Exercises 2.7.2 and 2.7.3.
Textbook Exercise 2.7.6.
(a) Is it true that the size or length of the result of an XPath query
over an XML document of length n is at most linear, that is O(n)? Either give a
counter-example or sketch an explanation for why this holds?
(b) Explain why a naive evaluation of XPath expressions could require
exponential time. As a concrete example, consider a simple document
<a> <b /> <b /> </a>
and the class of XPath queries q_n, where

q₀ = /a/b

q₁ = /a/b/../b

q₂ = /a/b/../b/../b

and q_n consists of q₀ followed by n pairs of parent-child steps of the form ../b .
Express and test XPath queries 1 - 14 of Section 5.4.1 in the Textbook
on the movies.xml document. The eXist database system is recommended for this, or
you can use the xpathTest application as a (less user-friendly) alternative.

Viimeksi muutettu: perjantai, 22 maaliskuu 2013, 09:58

Web Data Management (WDM)