Unni Cathrine Eiken February 2005

enriched by several new EPAS. Still, for the purposes of this thesis, the list includes a broad
enough variety of structures to be of use in the classification phase.
In the process of assessing the quality of the EPAS list, it became evident that the most
interesting structures are the simplest ones. The EPAS corresponding to verb-subject-object
relations are the ones that contribute with most information about the selectional restrictions of
the domain. An alternative way to obtain an effective and robust extraction of EPAS might have
been to concentrate only on this type of structure, rather that focusing on extracting all EPAS
from the text collections and then filtering out unwanted ones.
In order to estimate the potential of a classification of the EPAS list, line diagrams were created
using Formal Concept Analysis (FCA). FCA is a methodology of data analysis and knowledge
representation which identifies conceptual structures in data sets, and was a useful tool in the
process of identifying how the predicates and arguments in the EPAS list related to each other.
FCA distinguishes between two types of elements; formal objects and formal attributes. A
formal concept is seen as a unit consisting of all belonging objects and attributes (Wolff 1991, p.
430). Starting with any set of formal objects, all formal attributes the objects have in common
can be identified. When using FCA to structure the data in the EPAS list, the arguments were
termed objects, while the predicates were termed attributes. An FCA line diagram consists of all
objects and attributes in a given context, organised hierachically according to their shared
properties. Figure 5 below shows the FCA line diagram for part of the structures in the EPAS
list 4 . Each white label corresponding to an argument from the EPAS list should be understood as
a concept, and information about each concept can be read by following the upward leading
paths from each concept. An object has a given attribute if there is an upward leading path from
the object to the attribute (Wolff 1994, p. 431). Using the arguments/formal objects lensmann
(sergeant) and Fonn as a starting point, the associated predicates/formal attributes gi (give), and
bede-om (ask-for) can be identified. The arguments lensmann and Fonn co-occur with the
predicates gi and bede-om, while politi (police), which is further down in the hierarchy, cooccurs
with other predicates as well as those higher up in the diagram (gi, bede-om and bekrefte
(confirm)). In other words, more general concepts are found toward the bottom of the diagram,
while specialised concepts are found by following the paths upwards. For the data material in
4 The diagram was made using the program Concept Explorer, downloadable from
http://sourceforge.net/projects/conexp
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