text: In the bottom view of the Active ontology tab there is a tab called Ontology Prefixes. This tab shows all 
  the current namespace mappings in your ontology. There are certain concepts from OWL, RDF, RDFS, 
  XML and XSD that are required for every ontology, so those namespaces are by default mapped in every 
  new Protégé ontology. There is also a mapping to the empty string for whatever the namespace is for your 
  ontology. This allows you to display and refer to entities in your ontology without entering a namespace 
  prefix. If you look at that tab now you should see a row where the first column is blank, and the second 
  column has the base IRI for your ontology. It should be the same IRI as the Ontology IRI at the top of the 
  Active ontology tab, except it also has a # sign at the end. E.g., the Pizza tutorial developed for this 
  tutorial has an IRI of: http://www.semanticweb.org/pizzatutorial/ontologies/2020/PizzaTutorial and the 
  row that has a blank first column in Ontology Prefixes has the IRI: 
  http://www.semanticweb.org/pizzatutorial/ontologies/2020/PizzaTutorial#. 