## 4 Use Case
### Application to Water Supply Networks Management
Wikidata acts as a hub, providing links to other datasets such as GeoNames. Thanks to the enrichment, additional properties can be used in order to provide contextual information in the SPARQL queries that were unavailable in the original data source, such as population, coordinate locations and administrative territorial entities. ```
water:zone1 owl:sameAs <[[http://www.wikidata.org/entity/Q935589](http://www.wikidata.org/entity/Q935589)]([http://www.wikidata.org/entity/Q935589](http://www.wikidata.org/entity/Q935589))>. ```  
Listing 1: External links generated in RDF/XML. The RDF dataset has been evaluated using several methods: (i) nearly 40 constraints were defined and the data were validated against them using Stardog's Integrity Constraint Validation [46]; (ii) RDF data were validated by the W3C RDF validator (see [[http://www.w3.org/RDF/Validator](http://www.w3.org/RDF/Validator)]([http://www.w3.org/RDF/Validator](http://www.w3.org/RDF/Validator)) (visited on 4 February 2019)); (iii) acceptance sampling and manual revision was performed on several hundreds of records; and (iv) a procedure was implemented testing that the number of zones and subzones matches the numbers in the original data source. **Step 4. ** Data exploitation: LOD technologies allow the consumption of data in a different way to traditional systems by using federated queries that include external indicators from knowledge bases such as Wikidata and GeoNames. SPARQL allows the creation of queries such as the example in Listing 2 to retrieve the length of the supply network by zone and year. Based on the same dataset we have used in our experimentation, our study was focused on the analysis of potential relationships between indicators and enabling the discovery of goals that may be hidden [47]. Conversely, an initially expected relationship between the measure leaks and breaks in the network and water lost is not supported by the data. After the experimentation, the authors explained that it is necessary that the company reviews the way it is monitoring their goal. i.e., how the company is measuring breakdowns, or reviewing the suitability of the relationship, i.e., breakdowns do not \begin{table}
\begin{tabular}{l l} \hline \hline
**Prefix** & **URI** \\ \hline void & [[http://www.w3.org/TR/void](http://www.w3.org/TR/void)]([http://www.w3.org/TR/void](http://www.w3.org/TR/void))\# \\ rdf & [[http://www.w3.org/1999/02/22-rdf-syntax-ns](http://www.w3.org/1999/02/22-rdf-syntax-ns)]([http://www.w3.org/1999/02/22-rdf-syntax-ns](http://www.w3.org/1999/02/22-rdf-syntax-ns))\# \\ owl & [[http://www.w3.org/2002/07/owl](http://www.w3.org/2002/07/owl)]([http://www.w3.org/2002/07/owl](http://www.w3.org/2002/07/owl))\# \\ rdfs & [[http://www.w3.org/2000/01/rdf-schema](http://www.w3.org/2000/01/rdf-schema)]([http://www.w3.org/2000/01/rdf-schema](http://www.w3.org/2000/01/rdf-schema))\# \\ water & [[http://www.khaos.es/ontologies/lucentia/ontologies/water.owl](http://www.khaos.es/ontologies/lucentia/ontologies/water.owl)]([http://www.khaos.es/ontologies/lucentia/ontologies/water.owl](http://www.khaos.es/ontologies/lucentia/ontologies/water.owl))\# \\ wd & [[http://www.wikidata.org/entity/](http://www.wikidata.org/entity/)]([http://www.wikidata.org/entity/](http://www.wikidata.org/entity/)) \\ gn & [[http://www.geonames.org/ontology](http://www.geonames.org/ontology)]([http://www.geonames.org/ontology](http://www.geonames.org/ontology))\# \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Prefixes for namespaces. cause severe water loss. Other approaches can help in this matter, using external information in order to facilitate the decision-making process. ```
SELECT?year?value?unit WHERE{ water:zona6.3 water:hasLengthSupplyNetwork?length.?lengthwater:inYear?year.?lengthwater:unit?unit. ?lengthwater:value?value] ORDERBY?year }
```  
Listing 2: SPARQL query to list the length of the supply network by zone and year.