---+ Load and explore the Pirates data

We assume ClioPatria is still running and you are logged on, either as
=admin= or as a another user with at least _read_ and _write_ access.
The initial set of data is added to the _library_ as part of the
=pirates= packages and can be loaded using *|Repository/Load from
library|*.  Then select "=|pirates -- Piracy data|=" and click *load*.

---++ Explore the data

The main entry point for exploring the data is the menu
*|Places/graphs|*, which lists the datasets loaded into ClioPatria.
Select the topmost graph, which holds the piracy data. The two most
useful entry points are

  1. _predicates_, which lists all _relations_ in the graph
  2. _classes_, which lists the _types_ that are used in the graph

Note that RDF resources are web addresses, i.e., typically strings of
the form =|http://<host><path>[#fragment]|=. Many RDF tools and
languages allow for an _|abbreviated notation|_ by declaring a
_mnemonic_ that represents the (long) common prefix of RDF resources.
For example, the short form for
http://semanticweb.cs.vu.nl/2009/11/sem/hasPlace is

  ==
  sem:hasPlace
  ==

We defined prefixes for some commonly used resources in
the file =|config-enabled/pirates.pl|= that is part of the =pirates=
package. Prefixes are sometimes also referred to as _namespaces_.  See
also rdf_register_ns/2 and rdf_current_ns/2.


---++ The Web of Data

As you browse through the data, some links colored *red*. These are
resources that are not defined in the currently loaded dataset. Clicking
on such a link opens a page with information on where the resource is
used and the button *|Query the Linked Data cloud|*. Clicking this
button causes ClioPatria to retrieve the information from the resource
itself. In the ideal world, the resource (URI) points to an RDF document
that provides additional information about this resource. Similar to
links in HTML documents, the target may not exist, might not be a valid
RDF document, etc.

---++ Exercises

Use the ClioPatria browser (starting from *|Places/graphs|*) and answer
the following questions:

  1. What is the full resource and what is the meaning (according to its
  comment) of the predicate =|geonames_ont:featureClass|=?

  2. Piracy actions are modelled using *sem* (Simple Event Model).  Use
  the ClioPatria browser to find the main types and predicates that make
  up this model and draw a diagram that explains the main relations.

  3. =|sem:ActorType|= (the victim ship) and =|sem:EventType|= (what
  happened) are organised in hierarchies. Draw a diagram that explains
  how the _actorType_ hierarchy is organised.

  4. =|sem:subTypeOf|= is related to =|rdfs:subClassOf|=. Which relation
  is defined between these two properties?  What is the consequence of
  this for instances of the classes =|sem:ActorType|= and
  =|sem:EventType|=.
  
You are now ready to [[query pirate data with Prolog][QueryPirates.txt]].

@see [[Tutorial index][Piracy.txt]]