Towards declarative descriptions of transformations: An approach based on topic maps

Towards declarative descriptions of transformations:
An approach based on topic maps

Eva
Lenz

University of Bielefeld
eva.lenz@uni-bielefeld.de

Andreas
Witt

University of Bielefeld
andreas.witt@uni-bielefeld.de

Angelika
Storrer

University of Dortmund
storrer@hytex.info

2002

University of Tübingen

Tübingen

ALLC/ACH 2002

editor

Harald
Fuchs

encoder

Sara
A.
Schmidt

Introduction
The topic map standard ISO 13250 (Pepper 1999) provides an innovative and
standardized way to express information about documents.. Although the
relevance of topic maps for the humanities has been recognized, only few
applications in this area have been developed up to now.
In the following we will explain an approach for transforming document
collections which uses a topic map to express meta information. We believe
that this approach can be applied to various areas in the humanities where
information about documents is important, and will present two research
areas where our model can be employed: adaptive
hypertext and relationships between document
grammars.
Brusilovsky (2001) reviews the field of adaptive hypermedia. Adaptive
hypermedia systems build a model of the goals, preferences and knowledge of
the individual user and use this model during user interaction in order to
adapt the hypertext to the user's needs. Important application areas are
adaptive educational hypermedia and systems for managing personalized views
in information spaces. In this paper, we outline how topic maps can be used
to support the development process and maintenance of adaptive
hypertexts.
Document grammars define the structure of XML or SGML annotations using a
schema language. They can be used to check the validity of a document. The
oldest schema language is used for expressing document type definitions
(DTDs). Recently, a number of new schema languages have evolved in this
field, most of which use an XML syntax (Cagle et al. 2001). It can be
beneficial to formally express the relationships between two or more
document grammars. In the case of DTDs, these relationships can be described
using XML or SGML architectures as defined in an annex of ISO 10744
(HyTime). We will show how topic maps can be used to model relationships
between different document grammars, abstracting from the schema language in
which they are expressed.

Description of the model

Our model can be employed to describe and perform a transformation of a
collection of documents into a new one, taking into account a specific
context. In the following we speak of the initial
document collection (or the corpus)
and the generated document collection. The model
is based on a three-level information architecture (see figure), consisting
of
1. the document level: a corpus of
annotated documents,
2. the conceptual level: a knowledge
net, modelling relationships between the documents (or parts of
annoted documents) in the form of a topic map, and
3. the application context level:
information about the context in which the transformation is to take
place. For example, in the case of adaptive hypertext, this level
contains the user model.

A set of rules describes how the new document collection is to be generated
from the corpus, taking into account the state of the knowledge net and the
application context.
We use XML and related technologies for the implementation of this model.
This allows us to use and produce documents in the web context, and to apply
available tools (parsers, browsers, generators, validators). We assume that
all model components be expressed declaratively in an XML syntax: the
initial document collection, the topic map (Pepper & Moore 2001),
the information about the application context, and the rule language.
By expressing the rules in a declarative language instead of hard-coding them
into a programming language a level of abstraction is introduced. Each rule
can be regarded as a mapping which takes a condition (on XML documents) as
its input and produces an action (XML fragment) as its output. The
expressions allowed in the rules, and thus the type of transformation the
system is able to perform, are clearly defined by a document grammar.
The generation of documents is realized in two steps, comparable to the
implementation of the Schematron schema language (cf. Cagle et al. 2001, cp.
14). Each step is performed by an XSLT stylesheet. XSLT is a functional
programming language optimized for parsing and generating XML documents. The
first stylesheet takes the rules as its input and translates them into a
second XSLT stylesheet, i.e. it translates the abstract descriptions of
conditions and actions into an executable form. This second stylesheet takes
the initial document collection, the topic map, and the application context
information and generates the new document collection. This approach makes
the rules more compact, easier to understand, and easier to maintain than
program code.

Application A: Adaptive hypertexts
In the case of adaptive hypertexts, a collection of documents is tailored to
suit the user by adapting the content and the linking structure. Brusilovsky
(2001) describes a detailed taxonomy of the possible forms of adaptation,
which he calls adaptation techniques. Typically, the collection is filtered
(e.g., an expert of the domain sees other hypertext nodes and links as a
novice). Other adaptation techniques comprise sorting, visual annotation, or
"dimming" of links, as well as "stretchtext".
When we apply our model to the field of adaptive hypertext, the initial
document collection (on the document level) comprises all documents for
every type of user, whereas the generated document collection is a hypertext
adapted to one user. The relevant characteristics of that user are described
in the user model (application content level). For example, we could model
that users from a neighboring discipline "know" only certain concepts and
technical terms of the domain in question.
In the context of a project called HyTex (hypertext conversion based on
textgrammatical annotation, cf. Lenz & Storrer 2002) which is part
of a joint research group "Text-Technological Modelling of Information", we
model technical terms of a subject domain together with their relationships
in the form of a topic map (conceptual level). Different views on the
subject domain (on its concepts, technical terms, on their relations to
other terms and to documents) can be modelled using various topic map
constructions. These views correspond to characteristics of the user
model.
The rules describe how an adapted hypertext is to be created from the initial
document collection taking into account the user model and the topic map.
The code that has to be generated will always be very similar for the same
adaptation technique, e.g. for dimmed links. In this case, we would allow
"dimmed text" as a possible action in the rule language, and implement the
code once in the XSLT stylesheet.
We benefit from this approach in the HyTex project, as it allows us to test
different strategies for text-to-hypertext conversion, which can readily be
expressed in the form of declarative rules. The model can thus serve as a
tool in the area of hypertext research.

Application B: Expressing and processing relations between document
grammars
XML and SGML architectures (architectural forms definition requirements,
AFDR) allow one to express relations between two DTDs, a meta DTD and a
client DTD. They have been used in areas relevant to the humanities (Simons
1999). Software that can process architectures can automatically transform a
document annotated according to the client DTD into a document instance of
the meta DTD. This process is called derivation. Examples of use
include:
filtering document content,
filtering markup (e.g., transforming a richly annotated corpus
into a corpus with annotations specialized for a certain
purpose),
modifying markup (e.g., translating tag names from german to
english), and
changing attributes into elements and vice versa.

On the poster, we will show how document grammars - not only DTDs - and their
relationships can be expressed using a topic map, and how to apply our model
to generate derivations.
In this application scenario for our model, the initial document collection
contains documents annotated according to the "client" document grammar. The
generated ("derived") document collection will be annotated according to the
"meta" document grammar. The following steps have to be performed:
Translating the document grammars into a topic map (conceptual
level). This can be done automatically, e.g. using XSLT, when the
document grammar has an XML syntax.
Modeling the relations between the document grammars in the topic
map (conceptual level).
Specifying which documents are to be derived according to which
document grammar (application context level).
Describing the translation process by means of the rule
language.

Application B models the set of relations between document grammars as
defined in the AFDR, but our model allows for the extension of this limited
set.
This application of our model is used in the context of the project
"Secondary information structuring and comparative discourse analysis" (cf.
Sasaki et al. 2002). This project is also part of the joint research group
already mentioned.

Conclusion
We have described a model based on topic maps designed for a declarative
description of a document collection and transformations on that collection
in an application context. We have presented two important fields of
application for this model, but we assume that its application can be
extended to other areas relevant to the humanities.

Bibliography

Peter
Brusilovsky
Adaptive hypermedia

User Modeling and User-Adapted Interaction

11
1/2
87-110
2001

Kurt
Cagle

Jon
Duckett

Oliver
Griffin

Stephen
Mohr

Francis
Norton

Nik
Ozu

Ian
Stokes-Rees

Jeni
Tennison

Kevin
Williams

Professional XML Schemas

Birmingham
Wrox Press
2001

Eva
AnnaLenz
Angelika
Storrer
Converting a corpus into a hypertext: An approach using XML topic maps and XSLT

Proceedings of the Third International Conference on Language Resources and Evaluation (LREC-2002), Las Palmas

2002

Steve
Pepper
Navigating haystacks and discovering needles. Introducing the new topic map standard

Markup Languages: Theory & Practice

1
4
47-74
1999

Steve
Pepper

Graham
Moore

XML Topic Maps (XTM) 1.0

2001

TopicMaps.Org Specification.

Felix
Sasaki
Claudia
Wegener
Andreas
Witt
Dieter
Metzing
Jens
Pönninghaus
Co-reference annotation and resources: a multilingual corpus of typologically diverse languages

Proceedings of the Third International Conference on Language Resources and Evaluation (LREC-2002), Las Palmas

2002

Gary
Simons
Using Architectural Forms to Map TEI Data into an Object-Oriented Database

Computers and the Humanities

33
1/2
85-101
1999