=Paper=
{{Paper
|id=Vol-184/paper-15
|storemode=property
|title=Integrating Event Frame Annotation into the Open Ontology Forge Annotation Tool
|pdfUrl=https://ceur-ws.org/Vol-184/semAnnot04-15.pdf
|volume=Vol-184
|dblpUrl=https://dblp.org/rec/conf/semweb/WattarujeekritC04
}}
==Integrating Event Frame Annotation into the Open Ontology Forge Annotation Tool==
https://ceur-ws.org/Vol-184/semAnnot04-15.pdf
Integrating Event Frame Annotation into the
Open Ontology Forge Annotation Tool
Tuangthong Wattarujeekrit and Nigel Collier
National Institute of Informatics, National Center of Sciences,
2-1-2 Hitotsubashi, Chiyoda-ku, Tokyo 101-8430, Japan
tuangthong@grad.nii.ac.jp, collier@nii.ac.jp
Abstract. In this paper, we propose a scheme for event frame annotation
integrated into the Open Ontology Forge (OOF) annotation tool. This is a key
requirement for realization of knowledge description on the Semantic Web.
Semantic information contained in each event frame is a set of relationships
between a predicate and its arguments. As our aim is to keep OOF flexible for
various types of annotation projects, the scheme proposed in this paper is
designed based on the specialization three popular schemes: MUC-7’s template
relation, PropBank’s predicate-argument structure and FrameNet’s semantic
frame.
1 Introduction
This paper provides the scheme for the annotation of event frames which define
relationship information between objects or entities and their predicates indicating the
event. This scheme is being integrated into Open Ontology Forge (OOF)1, a free
annotation tool created in the PIA project [4].
As the Web of information readable by machines is the central concept of the
Semantic Web [2], Web pages require annotation to make instances of objects and
events explicit and to show the linkage to the context in which they occur. Thus, the
development of annotation tools becomes a focus of the research community (e.g.
GATE [6], MnM [9], OntoMat [10]). Like other semantic annotation tools, OOF tries
to reduce the effort required to create semantic annotated texts and it focuses mainly
on content annotation for Information Extraction (IE) as such we consider issues of
large-scale knowledge mark-up, inter-annotator agreement, ease of use by non-
linguistics, etc. One of the significant characteristics of OOF is that it not only
supports annotation but also provides for the creation of ontology and the linkage
between each instance and its occurrence in the text. To provide an environment that
integrates annotated texts with ontology promotes knowledge sharing.
The basic aim within the PIA project is to create an automatic information
extraction system by applying machine learning to annotated corpora [3]. At present
OOF can be used to construct annotated named entities (NEs) and coreference
relations [7]. It still lacks though the scheme to support the higher level IE task such
1 http://research.nii.ac.jp/~collier/resources/OOF/index.htm
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as event extraction task which provides facts in terms of relationships between entities
obtained from NE and Coreference task. Therefore, the event frame annotation
scheme needs to be integrated into OOF. With respect to our interest in the
application of IE to special domains such as molecular biology event extraction, we
currently plan to annotate molecular biology documents with semantics in terms of
event frame style following an extensible version of PropBank’s predicate-argument
structure [8] description.2 However, we also take into account other two popular
event frame styles among IE research groups (i.e. MUC-7’s template relation [5] and
FrameNet’s semantic frame [1]) in forming the scheme proposed in this paper. We
believe that the scheme which incorporates the key features of these three projects
will provide OOF the flexibility to be used by other research groups.
2 The Event Frame Annotation Scheme
Annotation of event frames will give web pages some machine readable information
describing a set of relationships between entities existing in each proposition. For
example, if the event buying in the expression “John is buying flowers for Marry.” is
annotated in an appropriate way, then not only can a machine understand that “John”
and “Mary” are persons, but also “John” plays role as “buyer”, “flowers” plays role as
“bought object” and “Mary” plays role as “receiver” in this buying event. So, various
applications such as IE can extract these important facts for users. Similarly, the event
frame annotation is capable of representing molecular events such as protein-protein
interaction also.
In general, different projects have their own perspective on how to define their
event frame or how a set of relationships in an event should be represented. Some
special distinctions3 of the event frame’s descriptions in three main projects of our
focus are illustrated in Fig. 1. However, all styles can be thought of as the general
frame-like styles which a relation or a set of relations is specified in an event frame by
a related predicate or set of predicates and related arguments or entities.
Descriptions of event frame defined by MUC-7,
MUC-7's PropBank's predicate- FrameNet's semantic PropBank and FrameNet influence in the designed
template relation argument structure frame scheme for OOF's event frame annotation.
Phrase/ Phrases Phrase/ Phrases
-MUC-7's frame represents the relationship between two
one or (NE is possible to (NE is possible to name entities. Each relationship in MUC-7's frame can be
more exist inside) exist inside) dictated by one or more predicates.
predicates
NE to define
NE one predicate to one or more predicates to -PropBank's predicate-argument structure represents a
define the relationship define the relationship predicate (usually verb) and relations in terms of the roles
the
of its argument (parts of the sentence surrounding it)
relationship Phrase/ Phrases Phrase/ Phrases -FrameNet's semantic frame represents relations in terms
(NE is possible to (NE is possible to of roles between arguments and predicates (same as
exist inside) exist inside) PropBank), but there can be more than one predicate
defined (same as MUC-7)
Fig. 1. The abstract view of an event frame from different projects
2 Reasons why we choose PropBank’s event frame style are out of scope of this paper. They
will be reported elsewhere.
3 Due to space limitation, only particular scheme’s points will be explained.
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2.1 Knowledge Model Issues
The knowledge model of OOF has several similarities to other ontology editors such
as Protégé-2000. An OOF ontology is centred around a frame-based knowledge
model consisting of classes, properties (slots) and annotations. Classes are related
through subsumption in a simple taxonomy. An event frame is managed as a subclass
of a root class, called an Event class. The argument participated in an event are
represented in the form of Event class’s property. Basically, property slot in OOF is a
binary relation between a domain (a class) and a range (a value data type). As an
event’s argument require being filled by more than one value, property of Event class
is necessary to be managed as a class rather than just a binary relation. A main
predicate of an event is modelled on a property of Event class as well. Moreover,
instances of basic class types in OOF are not abstract concept, but a surface-level
representation of the concept appearing in the document, in the form of texts or
images. Contrary to other class types, event instances are abstract entities but the
predicate itself and the arguments are realized as annotations in the text.
2.2 User Interface
As shown in the planned design of the new version of OOF in Fig. 2, OOF provides a
capability to view ontology, a Web page and annotated information concurrently.
Fig. 2. Event annotation screen shots
For event annotation, a user has to create a particular Event class first (cf. the red
E-icon). This process leads to the automatically construction of classes for the
predicate and arguments which are defined as properties of the Event class. Then, a
user can start annotating an event existing in a text by dragging and dropping the main
predicate to the Event class for that event. As shown in Fig. 2, the text “Blended” is
highlighted and assigned to the Event class blend (cf. arrow #1) to create an instance
blend#1 representing the event. Next, instances for event’s arguments can be captured
by highlighting some text elements and then using a hot key combination. In this
example, the text “Cabernet Franc” and “Cabernet Sauvignon” are captured for filling
argument slots blend-arg-0 and blend-arg-1, respectively (cf. arrow #2 and arrow #3).
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3 Discussion
There have been several annotation tools such as GATE of which rather focusing on
the annotation process embedded with language processing tools (e.g. POS tagger,
tokeniser) than the ontology editing; MnM of which distinct property is the supporting
of various representation language (e.g. DAML+OIL, RDF, WebOnto); and OntoMat
which provides many of the same features as OOF including ontology editing. In
contrast to these tools, the focus of our design is highlighting the role of the predicate
occurred in the text as the centre of the occurring event. The event itself is represented
as an individual object class rather than represented as a property of participated
entity. We believe that our thinking of predicate which is much closer to linguistic
perspective would allow OOF to be flexible for various event annotation styles.
The OOF has progressed forward in concerning more flexible scheme for event
annotation. However, OOF still requires the extension of event annotation scheme in
order to support nontrivial aspects such as to represent sequences of events.
4 Conclusion
We briefly presented the main scheme for semantic annotation of event frame being
integrated in Open Ontology Forge (OOF) tool, with the design to cover various styles
of event frames. The capability both to create ontology and to annotate texts as well as
to provide the linkage from the ontology instance to where it exists in texts makes the
OOF annotation tool worthwhile for Semantic Web applications. Current version is
downloadable from http://research.nii.ac.jp/~collier/OOF/index.htm. We plan on
releasing new version included event frame annotation capability in January 2005.
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