Sample Solutions for the XPath Exercises of Lab 2
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These are possible ways to express the queries of Lab 2. There are
also many equivalent solutions.



1. Return the area of Mongolia.

   string(//country[@name="Mongolia"]/@area)

   string(/descendant::country[@name="Mongolia"]/@area)


2. Return the names of all countries with population greater than 100
   million.

   //country[@population>100000000]/@name


3. Return the names of all countries where over 50% of the population speaks German. 

   //country[language[text()="German"][@percentage>50]]/@name


4. Return the names of all countries where a city in that country
   contains more than one-third of the country's population.

   //country[@population < 3*city/population]/@name


5. Return the population density of Qatar. Note: Since the quotes/
   operator has its own meaning in XPath, the division operator is
   infix div. So to compute population density use “(@population div
   @area)”.

   //country[@name="Qatar"]/@population div //country[@name="Qatar"]/@area


6. Return the names of all countries whose population is less than one
   thousandth that of some city (in any country).

   //country[@population < 0.001*//city/population]/@name


7. Return the names of all cities that have the same name as the
   country in which they are located.

   //city[name = parent::country/@name]/name


8. Return all city names that appear more than once, i.e., there is
   more than one city with that name. You may return a city name
   multiple times if it simplifies your query. (Hint: You might want
   to use the “preceding” and/or “following” navigation axes for this
   query.)

   //city[name = parent::country/following::city/name]/name


9. Return the names of all countries which have a city such that some
   other country has a city of the same name.

   //country[city/name = (preceding::city/name | following::city/name)]


10. Return the number of countries where Russian is spoken.

    count(//country[language = "Russian"])


11. Return the names of all countries that have at least three cities
    with population greater than 3 million.

    //country[count(city[population > 3000000]) > 2]/@name


12. Return the names of all countries for which the data does not
    include any languages or cities, but the country has more than 10
    million people.

    //country[not(language) and not(city)][@population > 10000000]


13. Return the names of all countries whose name textually contains a
    language spoken in that country. For instance, Uzbek is spoken in
    Uzbekistan, so return Uzbekistan.

    //country[language[contains(../@name,.)]]


14. Return the names of all countries in which people speak a language
    whose name textually contains the name of the country. For instance,
    Japanese is spoken in Japan, so return Japan.

    //country[language][contains(language,@name)]


15. Return all languages spoken in a country whose name textually
    contains the language name. For instance, German is spoken in
    Germany, so return German.

    //country[language][contains(@name,language)]/language


16. Return all languages whose name textually contains the name of a
    country in which the language is spoken. For instance, Icelandic
    is spoken in Iceland, so return Icelandic.

    //country/language[contains(self::*,parent::*/@name)]
    //country/language[contains(.,../@name)]