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Figure 3 - Example of “Rio de Janeiro” in Brazil.
 
 Figure 4 - Example of “Rio de Janeiro” in Peru. 
SOURCE: 
http://www.expedia.com/
Indeed, a request for the place name “Rio de Janeiro” sent to the ADL 
Gazetteer Server Client
3
will generate an ambiguous answer, which requires 
user intervention to be disambiguated. Table 1 shows the answer returned by 
the ADL Gazetteer, with the eight different feature types associated with 
places named “Rio de Janeiro”.
However, note that the answer could be automatically disambiguated 
using an associated vocabulary, such as a feature type ontology. 
 
 
3
http://middleware.alexandria.ucsb.edu/client/gaz/adl/

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Table 1 - Feature types of “Rio de Janeiro” instance in ADL Gazetteer Server. 
Place Names 
Feature Type 
Rio de Janeiro, Igarape - Acre, Estado do - Brazil
streams 
Rio de Janeiro - Brazil
populated places 
Janeiro, Rio de - Brazil
streams 
Rio de Janeiro - Loreto, Departamento de - Peru
populated places 
Rio de Janeiro, Serra - Paraiba, Estado da - Brazil
mountains 
Rio de Janeiro, Estado do - Brazil
administrative areas 
Janeiro, Rio de - Brazil
streams 
Rio de Janeiro, Serra do – Brazil
mountains 
SOURCE: ADL Gazetteer Server Client 
As a second example, we illustrate how to correct queries, using the 
reference ontology. 
Consider the following user query: “ Give me the State of Peru that has a 
City called Rio de Janeiro located in”. Suppose that we use RDQL
4
(RDF 
Data Query Language) as the catalog query language.
We note that one of the mayor advantages of RDQL is its ability to mix 
both metadata and instances in the same query.
Then, the above query would be formulated in RDQL as follows: 
1 
SELECT ?state 
2 WHERE (?id, , "Rio de Janeiro") 
3 (?id, , ?state) 
4 (?state, , ) 
5 (?state, , ?country) 
6 (?country, , ) 
7 (?country, , "Peru") 
The answer to this query will be NULL, because the first order division 
of Peru is not by states, but by “Departmentos”.
This failure can be avoided using a relaxation technique (
Chu and Mao, 
2000
), applied to ontologies. The relaxation technique consists in navigating 
thru the class hierarchy to generalize or specialize the query terms, 
expanding or reducing the scope of the user query.
The modified query will then be “ Give me the Departamento of Peru 
that has a City called Rio de Janeiro located in”, which in RDQL is: 
1 
SELECT ?state 
2 WHERE (?id, , "Rio de Janeiro") 
3 (?id, , ?state) 
4
RDQL: 
http://jena.sourceforge.net/tutorial/RDQL/

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4 (?state, , ) 
5 (?state, , ?country) 
6 (?country, , ) 
7 (?country, , "Peru") 
(Note that “
?state
” is a variable in RDQL and, hence need not be 
changed).