Game: Semantic stew

splashburgerInternet και Εφαρμογές Web

22 Οκτ 2013 (πριν από 3 χρόνια και 9 μήνες)

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Semantic Stew

the perils and potential of linked open data


The promise of linked open data, an element of the Semantic Web initiative, is that through the
aggregation of simple statements about named entities, computers can make useful inferences that provide
us with more and better information. Instead of being t
rapped within the unstructured Web of documents,
information expressed as linked open data can be more easily synthesized, manipulated, searched, and
otherwise processed by
software applications, the potential fulfilment of Paul Otlet’s dream of a world
kn
owledge base unencumbered by pesky document structure.


A great benefit of the linked open data approach is its extreme simplicity. Linked open data relies on just
a few basic elements:



Unique identifiers (URIs, of which the URL is a subset) to distinguis
h entities, properties, and
relations (things and concepts).



RDF, the Resource Description Framework, a way to describe the world through the expression
of triples (subjects, predicates, and objects).


This simplicity makes linked open data easy to gener
ate and disseminate.
However, with this simplicity
comes the potential for semantic conflict, when the same object (as referenced with the same URI) is
described in conflicting ways, or when the same property (as referenced with the same URI) is used in
di
fferent ways to describe different objects.
For example, the
datastore collected by Dbpedia, which
expresses Wikipedia infobox material as RDF, states that both Diana Ross and Amy Winehouse are
associated with the Jazz genre. We can debate whether these st
atements accurately portray either Diana
Ross, Amy Winehouse, or jazz, or even the idea of genre itself (is genre associated with a person or with
a work)?

Too, it is theoretically possible to write a triple that associates Bugs Bunny with Jazz, or the
st
ray cat that lives next door with Jazz.

























While it is possible to use more elaborate Semantic Web technologies, such as OWL, or the Web
Ontology Language, to constrain meaning, this gets quite complicated quite fast, and the beautiful
simplicity of basic RDF is lost.


So should we just throw up o
ur hands and declare
linked open data

an inevitable mess of catastrophic
proportions?
Well, maybe those semantic conflicts don’t really matter that much most of the time,
especially with enough data out there.
Determining which semantic conflicts do matter
, in what contexts
they matter, and what to do about it will be a key skill in the ultimate success of linked open data
applications.
(This is precisely the kind of task that you, my friends, should consider yourselves poised to
undertake!)


In this game,
we will see how this
kind of situation
might play out.
In groups, you will create triples
using defined sets of subjects, predicates, and objects, and you will draw your suite of triples as a graph.
Then you will see how your graphs integrate with other gr
oups, some of whom received the same set of
cards as your group, and some of whom received slightly different cards. Is there semantic conflict? Does
it matter?


Step 1. Create
triples and draw them as a graph.

(2
0

minutes)

Your group will receive
a set

of index cards.
Your cards will either be marked with a P or an O (for Paul
Otlet, historic precursor figure to the Semantic Web).


Each set of cards includes a group of subjects, a group of objects, and a predicate or two. For each
subject, create tripl
es using each appropriate predicate/object combination. Draw your triples on the
blank paper provided. Try to get all the triples
for your set

on a single sheet of paper, so that you can
show the different subjects linked to a single object (like Diana Ros
s and Amy Winehouse for Jazz).


Step
2
. Integrate your triples
with the other group
.
(20 minutes)

Draw another graph that aggregates the statements both groups have made. Is there semantic conflict in
the resulting graph? Does it matter?
If it does, how w
ould you handle it?