Muhammad Ali Norozi

226 Pages·2014·2.21 MB·English

Muhammad Ali Norozi
The Contextual Features in
Schema-Agnostic Environment
Thesis for the degree of Philosophiae Doctor
Trondheim, March 2014
Norwegian University of Science and Technology
Faculty of Information Technology,
Mathematics and Electrical Engineering
Department of Computer and Information Science
NTNU
Norwegian University of Science and Technology
Thesis for the degree of Philosophiae Doctor
Faculty of Information Technology,
Mathematics and Electrical Engineering
Department of Computer and Information Science
© Muhammad Ali Norozi
ISBN 978-82-326-0120-2 (printed ver.)
ISBN 978-82-326-0121-9 (electronic ver.)
ISSN 1503-8181
Doctoral theses at NTNU, 2014:98
Printed by NTNU-trykk
To Bibi Zahra, Maeda, Sani-E-Zahra and Sultana Ali Norozi.

Abstract
“Like your body your mind also gets
tired so refresh it by wise sayings.”
– ALI
Relevance scoring and estimation deals with both finding the relevant set of
answers and ordering them according to the degree of their relevance to the
user-intent. Thetraditionalinformationretrieval(IR)systemssuccessfullyfindand
ordertherelevantdocumentsandleavethemtotheusers, whothenhavetolocate
the relevant information embedded somewhere within the document. In contrast,
estimating relevance in semi-structured retrieval means not only retrieving and
ordering the relevant documents but also locating the relevant information within
the document as well. When it comes to semi-structured retrieval, the traditional
IR style retrieval is simply insufficient.
The main focus of this thesis is estimating relevance in a schema-agnostic environ-
ment. Here, “schema-agnostic” means that the schema or the structure exists ex-
plicitlywithinthedocumentsbuttheuserdoesnotorneednotknowthatschema.
In such an environment, the structure is generally defined loosely, which means:
(a) it can evolve over time, (b) it can constitute a large part of the data, and (c)
it might exist seamlessly within the document. The natural question that comes
into mind is, why is such a structure there at all? The structure in a schema-
agnostic environment is there to be used by retrieval systems for several useful
tasks. This thesis is about unveiling the capabilities of the structural constructs
within semi-structured documents in schema-agnostic settings.
Structural constructs can form what we call the structural context of the relevant
item. Astructuralcontextbuildsuptheinternalandexternalcontextualfeaturesof
a semi-structured document. These contextual features help with a series of tasks.
The work presented in this thesis contributes towards understanding and utilizing
the contextual features in the retrieval of focused information in schema-agnostic
settings.
During the course of this study we have identified, implemented and experimented
with several intuitive types of contextual features in semi-structured retrieval set-
tings. Contextualization isthegenericprocessofutilizingfeaturesinthestructural
context of the retrievable units in relevance scoring. The proposed retrieval ap-
proaches, based mainly on contextual features, exhibited notable improvements in
retrieval effectiveness, during empirical analyses.
i
Theevaluationsandempiricalanalysesareperformedinseveraltasks,spreadacross
different phases of this study. The tasks are performed by looking at different
aspectsandchallengesofthesemi-structuredretrievaldomain. Thefollowingtasks
areperformedatdifferentphasesofthisstudy: ad-hoctasks,granulationtasks,and
standard tasks offered by INitiative for the Evaluation of Xml retrieval (INEX).
The contributions of this thesis are also grouped by these tasks.
ii
Preface
“Often your utterances and expressions of your face
leak out the secrets of your hidden thoughts.”
– ALI
This doctoral thesis was submitted to the Norwegian University of Science and
Technology (NTNU) in partial fulfillment of the requirements for the de-
gree of philosophiae doctor. The work has been performed at the Department of
ComputerandInformationScience,NTNU,TrondheimandCentrumWiskuned&
Informatica (CWI), Amsterdam, the Netherlands. The doctoral program has been
supervised by Dr. Øystein Torbjørnsen (Microsoft Development Center Norway),
Professor Jon Atle Gulla, and Professor Svein-Olaf Hvasshovd. At CWI, the work
has been mentored by Professor Arjen P. de Vries. During the process, the candi-
date has been supported by the Information Access Disruptions (iAd) project and
funded by the Research Council of Norway and NTNU.
iii

Acknowledgements
“The value of each man depends upon the art and skill which he has attained.”
– ALI
Crafting the Ph.D. is like writing a book of poetry. Like poetry, you have
to get in love with a certain area, and, like poetry, from that loved area,
somethingnewandcreativeshouldsuddenlycomeintoyourmind. Eachandevery
sentenceiscraftedlikeaverseinpoetry. Hence,itisthebestofbothascienceand
an art. Science comes into play when you ascertain your imagination, everything
elseisart. Theartofideasandtheartofputtingthoseideasintoalimitednumber
of pages, with the help of science. When you start a Ph.D., a hard piece of rock
in the name of the Ph.D. topic is handed over to you. Throughout the years you
have to carve and craft that hard rock, tirelessly. By the end of this tiresome
journey you have to have one beautiful and monolithic sculpture out of that hard
rock, which will automatically reflect your creativity. In this thesis, I exhibit the
sculpture out of this work.
The thought provoking, formalized curiosity, and mind boggling yet creative expe-
rience of a Ph.D. is certainly not the work of one individual, the Ph.D. candidate.
Unfortunately, the names of those great people and things who made this work
possible should not be mentioned on the cover of this book, rather only in this
section. I name them as follows:
First and foremost, I thank my supervisors Dr. Øystein Torbjørnsen and Prof.
Jon Atle Gulla, for their endless support and encouragements. Our meetings were
an important source of knowledge and experience, which helped me to discover,
structure and clarify the ideas presented in this thesis. The iAD project is also
to be thanked for the annual meetings and get-togethers. They were fruitful and
enlightening. My deepest and heartfelt gratitude goes to my good friend and co-
author Dr. Paavo Arvola for his kindness, courage and easy going personality. I
alsoextendmywarmgratitudetoProf.ArjenP.deVriesforgivingmeanamazing
opportunity to stay and learn from the energetic group at the Centrum Wiskunde
& Informatica, Amsterdam.
Finally, Iwouldextendmydeepestloveandgratitudetomyfamilyandfriendsfor
their support, encouragement, and patience, which always kept me going, despite
hardships. Without your enduring trust, love, and support throughout all these
years, I never would have completed this work.
Muhammad Ali Norozi Trondheim 02.03.2014
v