Onto.PT: Towards the Automatic Construction of a Lexical Ontology ...

84 Chapter 5. Synset Discovery
tb-triples (synpairs) of CARTÃO (introduced in section 4), which establish a synonymy
network. However, this work was done before the last version of CARTÃO was available. The presented results were obtained with relations extracted using
the grammars of PAPEL 2.0 in DLP, DA (in a previous modernisation stage) and
the 25th October 2010 Wiktionary.PT dump.
5.3.1 Synonymy network data
Before running the clustering procedure, we examined some properties of the synonymy
network established by synpairs collected from the three dictionaries. Table
5.1 shows the following properties, typically used to analyse graphs:
• Number of nodes |V |, which corresponds to the number of unique lexical items
in the synpair arguments.
• Number of edges |E|, which corresponds to the number of unique synpairs.
• Average degree (deg(N)) of the network (see expression 5.5), which is the
average number of edges per node.
• Number of nodes of the largest connected sub-network |Vlcs|, which is the
largest group of nodes connected directly or indirectly in N.
• Average clustering coefficient CClcs of the largest connected sub-network,
which measures the degree to which nodes tend to cluster together as a value
in [0-1] (see expression 5.7). In random graphs, this coefficient is close to 0.
The local clustering coefficient CC(vi) (see expression 5.8) of a node vi quantifies
how connected its neighbours are.
deg(N) = 1
|V | ×
|V |
i=1
deg(vi) : vi ∈ V (5.5) deg(vi) = |E(vi, vk)| : vk ∈ V (5.6)
CC = 1
|V | ×
|V |
CC(vi) (5.7)
i=1
CC(vi) = 2 × |E(vj, vk)|
Ki × (Ki − 1) : vj, vk ∈ neighbours(vi) ∧ Ki = |neighbours(vi)| (5.8)
Weights were not considered in the construction of table 5.1. Since we have
extracted four different types of synonymy, considering the POS of the connected
items (nouns, verbs, adjectives and adverbs, see more details in section 4.2.4), in the
same table, we present the properties of the four synonymy networks independently.
POS |V | |E| deg(N) |Vlcs| CClcs
Nouns 39,355 57,813 2.94 25,828 0.14
Verbs 11,502 28,282 4.92 10,631 0.17
Adjectives 15,260 27,040 3.54 11,006 0.16
Adverbs 2,028 2,206 2.52 1,437 0.10
Table 5.1: Properties of the synonymy networks.