Sample Scenario

Let us now illustrate the usage of Explorator. Suppose the user needs to find all the lakes contained exclusively in Russia (and not in any other country). The task can be decomposed in the following steps:

1. Find all the lakes in the database;

2. Find Russia, the country;

3. Find all the lakes in Russia obtaining a set we will call LR;

4. Find the countries that share a boundary with Russia (Russia’s neighbors);

5. Find all the lakes in Russia’s neighbors, obtaining a set we will call LN; and

6. Build the set of the lakes contained exclusively in Russia by calculating the difference between the previous sets: LR-LN

To find all the lakes in the database, the user first searches for “lake”:

He locates the Lake class in the resulting set, and gets the set of instances of the Lake class by clicking on the Instances link, to obtain all the lakes in the database:

Next, to find Russia, he searches for “Russia” and locates the resource Russia in the resulting set:

To make sure he has the right resource, he views the resource details:

Next, to find all the lakes LR in Russia, he selects the set of all lakes and sets it as the subject of his query by clicking on the [S] toolbar button:

Continuing to build the query, he selects the resource Russia and sets it as the object of his query:

He executes the query to obtain the set of all lakes in Russia:

Next, to find the countries that share a boundary with Russia, he views the details of the Russia resource and locates the neighbor property in Russia, thereby finding its neighboring countries:

To find all the lakes in Russia’s neighbors, he selects the set of Lakes in Russia and sets it as the subject of his next query:

He selects the set of Russia’s neighbors and sets it as the object of his query:

He then executes the query to find all lakes in Russia’s neighboring countries:

Finally, to build the set of the lakes contained exclusively in Russia, he needs to calculate the difference between the set of lakes in Russia and the set of lakes in Russia’s neighbors. To do this, he selects the first set and the difference operator:

Finally, he selects the second set (containing the lakes in Russia’s neighbors) and executes the difference operation by clicking on the equal [=] toolbar button, thereby obtaining the desired result: