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The participants were given access to the corpus after some linguistic preprocessing had been done: for |
all data, a tokenizer, part-of-speech tagger, and a |
chunker were applied to the raw data. We created |
two basic language-specific tokenizers for this shared |
task. The English data was tagged and chunked by |
the memory-based MBT tagger (Daelemans et al., |
2002). The German data was lemmatized, tagged |
and chunked by the decision tree tagger Treetagger |
(Schmid, 1995). |
Named entity tagging of English and German |
training, development, and test data, was done by |
hand at the University of Antwerp. Mostly, MUC |
conventions were followed (Chinchor et al., 1999). |
An extra named entity category called MISC was |
added to denote all names which are not already in |
the other categories. This includes adjectives, like |
Italian, and events, like 1000 Lakes Rally, making it |
a very diverse category. |
3 |
http://www.ldc.upenn.edu/ |
Data format |
All data files contain one word per line with empty |
lines representing sentence boundaries. At the end |
of each line there is a tag which states whether the |
current word is inside a named entity or not. The |
tag also encodes the type of named entity. Here is |
an example sentence: |
U.N. |
official |
Ekeus |
heads |
for |
Baghdad |
. |
NNP |
NN |
NNP |
VBZ |
IN |
NNP |
. |
I-NP |
I-NP |
I-NP |
I-VP |
I-PP |
I-NP |
O |
I-ORG |
O |
I-PER |
O |
O |
I-LOC |
O |
Each line contains four fields: the word, its partof-speech tag, its chunk tag and its named entity |
tag. Words tagged with O are outside of named entities and the I-XXX tag is used for words inside a |
named entity of type XXX. Whenever two entities of |
type XXX are immediately next to each other, the |
first word of the second entity will be tagged B-XXX |
in order to show that it starts another entity. The |
data contains entities of four types: persons (PER), |
organizations (ORG), locations (LOC) and miscellaneous names (MISC). This tagging scheme is the |
IOB scheme originally put forward by Ramshaw and |
Marcus (1995). We assume that named entities are |
non-recursive and non-overlapping. When a named |
entity is embedded in another named entity, usually |
only the top level entity has been annotated. |
Table 2 contains an overview of the number of |
named entities in each data file. |
2.4 |
Evaluation |
The performance in this task is measured with Fβ=1 |
rate: |
Fβ = |
(β 2 + 1) ∗ precision ∗ recall |
(β 2 ∗ precision + recall) |
(1) |
Florian |
Chieu |
Klein |
Zhang |
Carreras (a) |
Curran |
Mayfield |
Carreras (b) |
McCallum |
Bender |
Subsets and Splits