Third Edition of the "XML and Information Retrieval" Workshop
First Workshop on Integration of IR and DB (WIRD)
Jointly held at SIGIR’2004, Sheffield, UK, July 29th, 2004
Ricardo Baeza-Yates, University of Chile, Chile
Yoelle S. Maarek, IBM Haifa Research Lab, Israel
Thomas Roelleke, Queen Mary University of London, UK
Arjen P. de Vries, CWI, Amsterdam, The Netherlands

Introduction
The morning session was dedicated to the third edition in the series of XML andInformation Retrieval workshops that were held at SIGIR'2000 (Athens, Greece, see
SIGIR Forum Fall 2000 issue) and SIGIR'2002 (Tampere, Finland, see SIGIR Forum Fall
2002 issue). The goal of the workshop, co-chaired by Baeza-Yates and Maarek, was tocomplement the INEX (Initiative for the Evaluation of XML Retrieval) meetings thathave been organized for the last two years, by providing researchers a useful forum fordiscussing (before implementing) and evaluating their models at INEX in the second halfof the year. Our intent was twofold: first encourage the exchanges of ideas between
researchers who are now active in this "sub-field" and, second, attract new interests. Our
focus, like in previous editions of the workshop, was to address issues related to theapplication of IR methods to XML data for querying, retrieval, navigating, etc. We havegone a long way since the first edition in 2000, when XML was entirely dominated by the
DB community. However, it seems that the expected breakthrough has not occurred yet,and it is not clear whether it is for lack of XML data, of appropriate technology, or
simply of real needs in the marketplace.
The afternoon session was dedicated to the first Workshop on the Integration ofInformation Retrieval and Databases (WIRD’04). The purpose of this workshop has been
to bring together researchers of the database (DB) and information retrieval (IR) fields,
facilitating exchange on the progress in developing and applying integrated IR+DB
approaches (or, naturally, DB+IR solutions). The three papers selected for the workshop
covered different aspects of data abstraction and DB usage for IR, illustrating how adifferent perspective on the integration leads to quite different views: a high level ofabstraction improves the development of advanced retrieval systems, following by a(layered) database architecture that may enable efficient processing of complex XML-IR
queries, or, where structured data could be used for query expansion in a more traditional
information retrieval setting. Also, it seems safe to expect to see several of the attendees
jumping on the general problem of ‘enterprise search’. We believe that the presentations
approaching the problem from different angles, and the ample opportunity for discussion,as well as the attendees’ inspiration triggered by the morning excellent keynote reallyhave made the workshop a forum for exchange on future DB+IR technology!

Invited talk: David Hawking, "A Panoptic View on Databases, XML and IR"
David Hawking from CSIRO in Canberra, Australia, was the invited speaker of both
workshops. He discussed his view on Databases, XML and IR from the perspective of anenterprise search engine, Panoptic, that started around 1999 and has now turnedcommercial, being deployed at around 35 sites. While this specific search engine isclearly not a major player in the enterprise world, it presents interesting features. The
latter were specifically designed for enterprise customers from various horizons (i.e., oil
exploration companies), who need to handle a mix of more or less structured documents
and meta-data, originating from heterogeneous sources, ranging from email and regular
documents to spreadsheets and DB records. Some of the issues that Hawking then rose
included the handling of heterogeneity, the distinction between the notions of value andof relevance in search results, indexing DB entries as opposed to the Web pages derived
from them, and more generally the boundaries between IR and DB.
Hawking then illustrated his purpose with technical examples on how Panoptic supports
semi-structural queries, relying on meta-data classes. The basic idea is to map meta-dataclasses to single letters of the alphabet, hence a query for "Baeza-Yates" in an author
field (be it specified in XML or originating from a DB table) will be expressed as“a:Baeza-Yates".

Hence, the number of classes is limited to 26 letters, which according to Hawking is in
most cases largely sufficient. He made the point that this approach raises the lowest
common denominator for search over combination of web pages, email, xml, db (overtext), through a single mapping instruction, which is feasible in an enterpriseenvironment. He gave some more details on the query language, which is not Boolean(often found too complex by many). An implicit "and" is assumed between all query
terms and alternatives can be specified via square brackets. In addition, wildcard andspecial operators are supported. An example of valid query is given below:"workshop on db and ir" [a:Maarek a:Marek] p:ibm d>feb
where the square brackets indicate alternative spellings and d is a reserved token for

dates. In terms of implementation, Panoptic uses db2xml plus a JDBC bridge to convert
DB records to XML files, and records/fields to be indexed are selected via SQL queries.
Hawking concluded his talk by raising the question of how far an IR system should go.
As an example, he asked whether joins and set computations are really needed. In orderto advance the field, he believes that what is needed is a common heterogeneousenterprise search collection consisting of an actual Intranet website, enterprise DBs,
email, shared file systems contents, etc, together with actual queries. He hopes that suchcollection could be assembled and be used for making research progress, maybe in thecontext of a new TREC track.

XML and IR
The XML and IR morning session consisted of 4 papers that were selected by theworkshop PC1. David Carmel from IBM Haifa Research Lab opened the session bypresenting a paper co-authored with Broder, Maarek, Mandelbrod and Mass, which dealt
with "Extending the XML Fragment Model to Support Querying over Annotated Text".
The motivation for that work is to adapt and extend the XML Fragment model(introduced at a previous edition of the workshop and formalized at SIGIR'03) so as toaccommodate for text annotations, which might be overlapping. Carmel first reminded tothe audience the key ideas behind the XML Fragment model, where XML collections are
queried via pieces of XML, or XML fragment, of the same nature as the documents
forming the collection, in the pure IR spirit. He illustrated his purpose by giving a few
examples of how information needs are expressed in XML Fragments. He then explained
how certain automatic semantic annotators, such as developed in the context of IBM's
Unstructured Information Management Architecture (UIMA) effort, do not generate validXML. Indeed the annotations being generated on a same piece of text can easily beoverlapping, and overlapping tags cannot be represented in XML either at the document
or at the query levels. To answer this need, Carmel and his colleagues proposed to
introduce new operators, namely for the intersection and concatenation of tags. He
detailed the syntax and semantics of these operators and a small discussion started where
several workshop participants expressed their interest and discussed how they had been
confronted with similar constraints in computational linguistics applications.
The second presentation was given by Ludovic Denoyer, from University Paris 6, anddealt with "Document Mapping for Heterogeneous Corpora". This work was conductedjointly with Wisniewski and Gallinari at the LIP6 Lab. Denoyer first explained how
dealing with heterogeneous XML corpora is pretty complex due to the variety of schemas
or DTDs. In order to allow search engines to handle different formats or document types,
he proposed as an option to use mediators, which would transform queries anddocuments. The ultimate goal is to find a relation between different structures andschemas, or in other terms, address the "schema matching task" (as known in the DBcommunity) from an XML perspective. Denoyer explained that this task can be divided
into the following sub-tasks: (1) learn the correspondences between tags, and (2) matchtags in a "1-on-1" or "n-to-m" manner. However, in IR the context and tasks are different,
indeed, the source DTD/schema is often unknown, the order of content elements might bemeaningful, the number of tags might be much larger than in DBs (in the INEX corpus
there are more than 100 tags), tag names often carry weak semantic, etc. Due to the highcomplexity, and the different needs, he argued that in most cases, approximate mapping
may be sufficient, which thus allows for machine learning techniques. He proposes tolearn the mapping from the data, and have it depend on both structure and content. In thisapproach, the document model is represented stochastically, via two probability
distributions: a structural probability and a content probability. The structural probability
is computed as a join probability (e.g., so as to model the probability to see a "title" tagunder a "doc" tag), and a content probability, using a local naïve Bayes model. Then, in
1

The XML and IR workshop PC consisted of M. Consens, M. Gertz, T. Grabs, D. Hawking, J. Jose, M.
Lalmas, Y. Mass, P. Raghavan, and D. Suciu, whom we thank for their thorough work here.

order to find the structure of a new document, mediator tags that maximize theprobability of a document need to be learned. He concluded showing the experiments that
he and his colleagues run on the INEX corpus, by splitting it and removing part of thetags in order to simulate a heterogeneous corpus. The results were encouraging anddemonstrated that using a combination of structure and content was best. He still
believes though, that more tests and real heterogeneous corpora are needed before fully
validating his approach.
The third paper of the session was presented by Karen Sauvagnat, from IRIT. This work,
jointly authored with Mohand Boughanem, discussed "The impact of leaf nodes
relevance values evaluation in a propagation method for XML retrieval".
Sauvagnat first reminded the fundamental difference between the DB and IR views interms of the roles of relevance and efficiency in XML retrieval. She surveyed previous
work by Goevert et al in 2002, on augmentation methods, where indexing weights are
assigned to inner nodes by propagation from leaves. She introduced then the XFIRM
model, where, in the same spirit, all leaf nodes are indexed, and the weight of inner nodes
is computed based on the distance that separates nodes in the tree. Sauvagnat also
described both, the logical and physical data representation models, used in her approach.
The XFIRM query language is based on a complete query language (keywords withphrases, AND & OR operators, structural conditions, and even hierarchical conditions in
its more complex form) that looks like a variant of XPath. She also detailed the query
processing mechanism, where each query is decomposed in elementary sub-queries thatare then processed independently. Each node is consequently assigned a relevant value,
which is propagated up the tree, and then sub-queries are reconstructed (using the nearest
common ancestor for instance). Sauvagnat also presented the experiments her teamconducted on the INEX collection, with the strict CAS measure, which were positive. She
concluded by explaining that this work should be considered as a starting point forfinding an appropriate formula for leaf nodes relevance values evaluation. Possible
directions of future research would be to evaluate different formulas taking into accountthe type of the elements to be returned, the length of the element, etc.
The final presentation of the session was given by Huyen-Trang Vu, from Paris 6
University. She discussed her joint work with Piwowarski and Gallinari, also from LIP6,
entitled "Filtering in XML Retrieval: a Prospective Analysis". One key challenge ofXML retrieval is to reduce or avoid overlapping results induced by nested elements. In
this work, she proposes to use filtering as a post-processing mechanism to remove
redundant results. The post-processing mechanism consists of three phases: re-scoring,filtering and final scoring. Re-scoring is based on the "utility theory" as defined by
Crestani et al, and a novelty score to be balanced with the original relevance score.
Filtering can be conducted in two manners: the first type is related to adaptive filtering,
while the second is based on a recursive process of the document tree. Both strict and"tolerant" filtering techniques (where some overlaps are allowed) are considered. Finally,
she discussed two different strategies for overall scoring. Vu then explained how sheplans to use the INEX collection to analyze nesting and analyze and compare various
filtering strategies.

IR and DB Workshop
The afternoon session was dedicated to the First WIRD workshop (co-chaired by Thomas
Roelleke and Arjen P. de Vries) and consisted of three papers selected by the workshop
PC2. Ingo Frommholz from Fraunhofer IPSI started by presenting COLLATE an
indexing and retrieval system for an historical film archive. It provides film researcherswith a collaborative environment in which historic documents about European films canbe analyzed, interpreted, and discussed, using nested annotations and discourse structure
relations among them. First, discussion about films is represented by free text
annotations. Also, the system indexes the annotations of annotations, which is where thediscourse structure enters the game. At the moment, the collection studied consists ofalmost 7000 documents and 2000 annotations. The COLLATE system has been
implemented using four-valued probabilistic Datalog, which distinguishes itself fromother approaches by basing the inference on the open-world assumption: negative andpositive evidence are treated independently, so the absence of p(a) does not automatically
imply not(p(a)). Ingo then explained how query processing takes place in the current
prototype implementation. Further research is planned to validate experimentally the
impact and significance of using annotations as proposed.
Vojkan Mihajlović, a PhD student at University of Twente, presented the second paper in
the afternoon, posing the question whether an ‘XML-IR-DB sandwich’ would taste betterwith ‘an algebra in between’. He argued that the traditional, layered database architecture
is very suited for the development of XML-IR systems, and allows the development ofstructured document retrieval systems on top of relational database systems. The paper
focuses specifically on the role of the logical level in the proposed system architecture.
This intermediate layer between the XML level and the relational database system serves
three goals: expressing XPath expressions and about clauses requires operators that are
not available in the relational database system, it allows for query optimization, and, it
allows expressing the propagation of scores through the query expression. He presented
first a ‘Boolean’ region algebra to explain the general idea, and then moved on to aranked region algebra for expressing more powerful retrieval models. Vojkan finallymotivated the potential for query optimization based on some well-chosen examples ofrewriting expressions using the algebraic properties of the operators.

2

The WIRD’04 PC consisted of S. Chaudhuri, I. Frommholz, N. Fuhr, T. Grabs, D. Hiemstra, U.
Kruschwitz, A. Natsev, J. Shanmugasundaram, D. Suciu, and M. Taylor.

The final talk of the afternoon, given by Cheng Xiang Zhai from the University of Illinois
at Urbana-Champaign, motivated Entity Retrieval from a collection consisting of both
structured and unstructured data. The specific task studied in the paper is to find all web
pages for a certain researcher (the entity). When compared to ‘traditional’ databasesearch, the entity retrieval problem is challenging because it would require search at asemantic level instead of the syntactic one that can be expressed in SQL queries, e.g. due
to ambiguous names. When compared to full-text retrieval, the difference is that entity
retrieval involves a special type of information need, more objectively defined than the
one usually studied in information retrieval experiments. Cheng Xiang and his students
have shown in their research work that a full-text search in a (newly constructed) testcollection of web pages improves when taking structured information from the DBLP
data into account for query expansion.

Discussion
The joint workshop ended with an open discussion among participants, with the main
goal to identify the issues in the integration of databases and information retrieval, andthe potential role of XML. We opened the discussion by asking why the workshops hadreceived a smaller number of submissions than expected (8 for the XML and IR
workshop and 4 for WIRD). It was not clear whether it was due to the large number ofworkshops held at SIGIR or the fact that, while sufficient interest exists in the main
topics addressed by the workshops, the area of interest might better be captured under thenotion ‘enterprise search’. Here, David Hawking advertised the upcoming Enterprise
Search task at TREC, intended to (eventually) replace the web-track. He gave someinsight in the plans, notably the data most likely to be used (W3C collection, and maybe
cleaned-up Enron data), and the track set up (includes a collaborative relevanceassessment phase).
We proceeded by eliciting the audience’s opinion on the most important topics that
require further research. This session lead to a varied number of issues, summarized here
into the following partial list:• Semi-structured search, ‘intelligent search’, ‘enterprise search’.
• What do the appropriate query languages look like?
• What is the amount of heterogeneity (in structure) of the data to be searched?
• How do we evaluate proposed techniques?
• How to achieve efficient and scalable search systems?
• Do we need ontologies?
• How does this all relate to ‘customer relationship management’?

Figure 1: Snapshot of the board during the discussion

Next, a decentralized brainstorm session started in an attempt to classify the wide variety
of issues found into a more organized structure. At some time during this discussion, thegraphics depicted above ‘appeared’ on the blackboard; notably a graph showing‘expressiveness of the query’ on the X-axis (‘keywords’, ‘XPath (+about)’, ‘structured
queries (+about)’ and eventually ‘natural language’) and ‘amount of structure in the data’on the Y-axis (‘text’, ‘XML’, ‘structured’, ‘knowledge base’), where IR would cover the
lower left corner, then XML-IR a wider area, DB an even wider area, and artificial
intelligence being the field that covers all topics… although not all of us agree on thislatter view!
Summarizing the opinions expressed in the group discussion, most workshop participants
seem to view the ‘integration of DB and IR’ as an intermediate step toward truly‘intelligent search’, and this intermediate step being the missing link to build searchengines for enterprise data.