text: To understand what is going on you first need to understand that each SPARQL query consists of two 
  parts. The first part at the beginning consists of several namespace prefixes. These statements consist of 
  the prefix used for a particular namespace as well as the IRI associated with this namespace. Recall that 
  these concepts were described in chapter 7. You may be wondering where all these prefixes came from 
  since you didn’t add them to your ontology. The answer is that every OWL ontology comes with a set of 
  namespaces and prefixes that are required to define the ontology. 
  
  Also, to understand SPARQL you need to “peak under the hood” of OWL. So far, we have been 
  discussing concepts in purely logical and set theoretic terms, i.e., at the semantic level. However, like any 
  language or database there is a lower level that describes how the concepts are mapped to actual data. In a 
  relational database the fundamental construct to represent data is a table. In OWL the fundamental 
  construct is a triple. OWL is actually built on top of RDFS which is a language built on top of RDF. RDF 
  (Resource Description Framework) is a language to describe graphs (in the mathematical sense of the 
  term). I.e., to describe nodes and links. 