=Paper=
{{Paper
|id=Vol-184/paper-11
|storemode=property
|title=Managing the semantics of coreference relations with Open Ontology Forge
|pdfUrl=https://ceur-ws.org/Vol-184/semAnnot04-11.pdf
|volume=Vol-184
|dblpUrl=https://dblp.org/rec/conf/semweb/KawazoeKC04
}}
==Managing the semantics of coreference relations with Open Ontology Forge==
https://ceur-ws.org/Vol-184/semAnnot04-11.pdf
Managing the semantics of coreference relations with Open
Ontology Forge
Ai Kawazoe Asanobu Kitamoto Nigel Collier
National Institute of Informatics
2-1-2 Hitotsubashi Chiyoda-ku
Tokyo 101-8430 JAPAN
{zoeai, kitamoto, collier}@nii.ac.jp
Abstract. In this paper, we will discuss managing the semantics of “corefer-
ence relations” in the framework of the Semantic Web. In the Semantic Web
context coreference is important in integrating many kinds of information
sources (of various linguistic forms, images, etc.) and helping users to share
such information. In this paper we propose a knowledge model for describing
the semantics of co-referential identity relations on annotations, and introduce
the Open Ontology Forge (OOF) software to support users to manually anno-
tate coreference in texts and between images and texts.
1 Introduction
In this paper, we will discuss how to manage the semantics of coreference by human
experts. In the domain of natural language processing, coreference has been a key
problem for computers to understand the meaning of natural language texts through
anaphoric expressions that require disambiguation, and accurate identification of
coreference makes it possible for computers to maximize the amount of useful infor-
mation. In the Semantic Web context, “coreference” play a role not only in augment-
ing information, but also in integrating information sources which refer to the same
class instance and helping users to share the information. So far, the Semantic Web
initiative [1] has enabled RDF [5] and OWL [7] to become a common meta-data stan-
dard for sharing knowledge on the World Wide Web, and this allows for the explicit
description of concepts, properties and relations in an ontology. Instances of concepts
in an ontology appear in documents in many different forms (ex. various linguistic
forms, images, etc.) and in order to integrate information it is necessary to manage the
coreference relations between such surface forms.
In this paper we outline a knowledge model for describing the semantics of corefer-
ence on annotations implemented within Open Ontology Forge (OOF), software to
support users for annotating coreference relations by hand. The coreference cases
which we aim to deal with in this work are taken from the domain of molecular biol-
ogy and include 1) coreference among linguistic expressions including anaphoric
relations (ex. Interleukin-2…it) and term variations (ex. Interleukin-2 vs. IL-2), 2)
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multimodal coreference among texts and images (ex. a biomedical image of a cell and
description of the cell in a figure legend), and 3) cross-document coreference.
2 Representing Coreference
In the OOF knowledge model, we represent coreference relations as illustrated in
Fig.1. In this model, co-referring expressions are related to what we call a “corefer-
ence pool” which is linked to an ontological class.
……………………………………..
…………………………………….
text1
…………………………………….
text2
…………………………………….
…………………………………….
Ontological class 1 Coreference pool1
…..
Coreference pool2 ………………
……………….
text3
……………….
Ontological class 1
……………….
………………..
Image1
ontology Coreference pools documents
Fig. 1. Overview of the coreference annotation model.
The important feature of the model here is that the co-referring expressions in a
coreference pool have the same status (unlike “coreference sets” in Conceptual
Graph) and there is no hierarchical relation among them. Each of the expressions,
regardless of their type, are independently related to a coreference pool. From a prac-
tical point of view, we can say that this style of annotation is one of the easiest ways
to represent cross-modal and cross-document coreference. Also in intra-text corefer-
ence annotation, it will reduce a lot of user efforts and make no assumption of lin-
guistic training, especially in that it does not require specifying antecedents for pro-
nouns or canonical forms for names, unlike other schemes such as MUC [4].
3 OOF annotation support tool
We have developed the OOF software to support users in annotating coreference
relations by hand. The main features of the software are 1) an integrated function for
ontology creation and text/image annotation, and 2) a user interface which realizes an
easy way of annotation for cross-modal items. OOF has a full Web-browser view of
a html document, along with a window showing the ontology and coreference pools.
Users can create the class hierarchy by expanding the root class and defining new
class names. The software allows for two modes of instance capture: the named en-
tity annotation mode and the coreference annotation mode. In both, users can make
text annotation by dragging and dropping the selected part of text (Fig.2) to the class
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in the taxonomy. For image annotation, OOF has an SVG editor window for select-
ing a part of image and editing properties as in Fig. 3. The selected part of the image
can be linked to an ontological class or a coreference pool in the same manner as
texts: a simple drag-and-drop fashion.
Dragging and dropping of an item under the appropriate class
creates a new coreference pool
Dragging and dropping of a co-referring expression to the
Dragging and Dropping of a selected item to the ontological class coreference pool will add the expression to the pool
will add the item to the class.
Fig. 2. (left) Named entity annotation and (right) coreference annotation with OOF.
Drag & drop the
part of image into
a coreference pool.
Users select one of the
basic shapes and clip the
part of image.
Fig. 3. (left) A window for image editing. (right) Annotation of text-image coreference
The OOF knowledge model has several similarities to other ontology editors such
as Protégé-2000 [6] and OntoEdit [8]. What distinguishes OOF is its focus on pro-
viding support for content annotation. An annotation in OOF is regarded as an in-
stance with a linkage to the document and tracking information about the annotator,
recorded by the pre-defined properties including (1-3) below, whose values are auto-
matically assigned by the software. Annotations are grouped within ‘coreference
pools’ via (4), and (5) and (6) to record characteristics of instances.
1. XPointer takes an XPointer value [2] and relates an annotation to the resource
2. author is a name of the author of the annotation
3. ontology_id relates an annotation to an ontological class
4. pool_id takes an ID of the coreference pool to which the item belong
5. expression_type specifies the subtype of the instance (name, pronoun, image, etc.)
6. svg records a description of the annotated part of image in SVG [3].
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4 Discussion
We have conducted two kinds of annotation case studies using OOF: 1) annotation of
biomedical articles (text only), and 2) annotation of documents which include images
of Buddhist statues in Dunhuang. We had two biologists and some experts in the
cultural heritage domain as annotators, who are not experts in NLP. In the former
experiment, the annotators seemed to have a good understanding of the notion of
coreference pool, and they made coreference annotations in the way we have intended.
However, since the current version of OOF does not have semi-automatic annotation
function for coreference, some coreference relations were left unannotated. The latter
experiment have revealed some limitations of the current OOF knowledge model.
For example, when annotating an image of a Buddhist statue, users sometimes want
the same image to be both under a class of styles (ex. Ghandara_style) and under a
class of motifs (ex. Bodhisattva), but OOF does not allow such annotation. Further,
relations such as a part-of relation seem necessary, where we are describing the rela-
tionship between a Buddhist statue and its halo. We should reconsider how to man-
age these situations with OOF.
5 Concluding remarks
Open Ontology Forge was released in February 2004 and available freely for
download from http://research.nii.ac.jp/~collier/resources/OOF/index.htm. We plan
to release a new version of OOF in December 2004 with several functions including
multi-document annotation.
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