Developing Community-Oriented Metadata Vocabularies:
Some Case Studies
Shigeo Sugimoto1, Wonsook Lee2, Mika Murotani2, Mitsuharu Nagamori1,
Mitsuyoshi Moriyama3
Institute of Library and Information Science, University of Tsukuba, andUniversity of Library and Information Science, Tsukuba, Ibaraki, Japan
2 Graduate School of Information and Media Studies, University of Library andInformation Science, Tsukuba, Ibaraki, Japan
3 Okayama Prefectural Culture Center, Okayama, Okayama, Japan
1

Abstract
The Internet has made possible a global information
environment where we can access information
resources regardless of distance. However, current
Internet technologies have not sufficiently matured
yet to provide a community-oriented information
infrastructure where a user can access information
resources using terms and metadata schemas
designed for his/her community. Metadata plays animportant role to help realize a community-oriented
information environment.
This paper presents two case studies which
include the development of domain-specific subject
vocabularies – a core subject vocabulary for a subject
gateway for library and library-and-information
science (LIS) resources, and subject vocabularies of a
portal service for a regional community. These casestudies show that small subject vocabularies areuseful for these community-oriented services, andthat maintenance is a crucial issue for thedevelopment and use of the vocabularies.
In order to build a community-oriented
information environment in the Internet, we have tosolve two contradictory requirements for metadata
schemas – specialization (or localization) in acommunity and interoperability among communities.
This paper shows a conceptual model to understandcrucial aspects to solve the contradictory
requirements.

1. Introduction1
The Internet and WWW have made possible a global
information environment. The progress of the Internet

1 The studies described in the paper are supported
in part by JSPS Scientific Research Grant#15300078 and a collaborative research project
grant between Infocom Corporation and the
Research Center for Knowledge Communities,
University of Tsukuba.

over the past ten years has significantly changed our
information environment. Internet search engines anddirectory services such as Google and Yahoo! havebeen globally accepted as a basic service to help
users access information resources on the Internet,
and digital libraries have been recognized as afundamental
functioninlibraries
andinformation-centric organizations for their users. On
one hand, this progress has produced global
accessibility to information resources for individual
users, i.e., geographical distance is no longer afundamental barrier to access information. On theother hand, the diversity of user communities andinformation resources often causes difficulties for auser to find appropriate information from vast
amounts of information resources on the Internet.
Community is an important factor to solve thedifficulties because meaning of words and phrases
often depends on communities. In other words, acommunity oriented vocabulary is an importantresource to realize a community oriented information
environment.
Metadata, which has been widely recognized asa key component for the Web and digital libraries invarious aspects, is obviously important to create acommunity-oriented information environment. Localor domain-specific communities would need to define
metadata schemas and controlled vocabularies inaccordance with their requirements in the case that
their requirements are difficult to be satisfied only by
those defined for the global communities. On theother hand, community-oriented specialization ofschemas and vocabularies would raise a bar forinteroperability issues for cross-community use of
metadata and information resources. In addition,
long-term maintenance of the schemas andvocabularies is a crucial aspect for the communities.
Thus, we need to satisfy the contradictory
requirements to metadata in order to create acommunity-oriented information environment.
The central topic of this paper deals withvocabulary of terms included in metadata schemas. A

metadata vocabulary is a set of terms defined in a
metadata schema. In general, there are two types of
metadata terms – terms that define properties ofresources and those that define schemes to encode
property values. In this paper, we use “metadata
vocabulary” as a generic term that means both ofthese two types. We use “property vocabulary” and“value vocabulary” to mean vocabulary of resource
properties (or metadata elements) and encoding
schemes, respectively. We use “subject vocabulary”
to mean a value vocabulary to express subjects ofresources.
For
example,Dewey
DecimalClassification (DDC), Nippon Decimal Classification(NDC), and Library of Congress Subject Heading(LCSH) are subject vocabularies. This paper shows
two case studies and a conceptual model of metadata
schema. In both of the case studies, subject
vocabularies for domain and community-oriented
metadata have been investigated. The conceptualmodel proposes to split metadata vocabularies andstructural (or syntactical) constraints of metadata
schema in order to identify requirements for metadata
interoperability.
The rest of this paper presents two case studiesof metadata centered research and a conceptualmodel of metadata schema for interoperability. The
first case study is a development of a subject
vocabulary for the ULIS-DL metadata database thathas about 27000 records of Simple Dublin Core
metadata for Web resources published by and/or
useful for libraries and library and information
science (LIS) institutions. The study has created areasonably small set of subject terms, which we callcore subject vocabulary that includes about 1000
terms and covering approximately 90% of theresources collected. We have developed an
XML-based software to create a subject directoryfrom the metadata database using the core vocabulary
which is encoded in Web Ontology Language (OWL).
Section 2 describes ULIS-DL and the core
vocabulary.
The second case study is a development of a setof vocabularies for an information navigation service
named Digital Okayama Dai-Hyakka (Digital
Encyclopedia of Okayama). This navigation service
collects Web contents published by and/or for the
local communities and provides links to the resources
with simple and descriptive metadata. DODH
assumes both librarians and non-professionals as its
catalogers. Its metadata schema is defined based on
Simple Dublin Core and it uses a subject vocabulary
designed for the local community. Section 3 describes
DODH and its basic design issues.
In section 4, this paper describes a conceptualmodel of metadata which is proposed to understandrequirements for interoperability of metadata. This
paper presents a layered model of metadata schema inorder to separate application specific and neutralcomponents and to separate semantic and syntactic
components. This explicit separation is useful toidentify interoperability between schemas andfunctional requirements to use metadata acrossmultiple schemas. A metadata schema registry
designed for Dublin Core is discussed based on themodel.
Section 5 discusses the vocabulary issue fromthe aspects of maintainability, interoperability andre-usability of subject vocabularies and metadata
schemas.

2. Development of a Core Subject
Vocabulary for ULIS-DL
2.1 Overview of ULIS-DL
The Digital Library service at the ULIS Library(ULIS-DL) started in February 1999[7]. The principal
purpose of ULIS-DL is to build a subject gateway toresources useful for libraries and LIS institutions. We
have collected the resources published by libraries
and LIS institutions mainly in Japan, and created
metadata for the resources. The metadata element set,called ULIS Core, is defined based on the 15 Simple
Dublin Core elements with a few ULIS-DL specificelements. Pronunciation information is included as an
optional sub-element of every element. As of summer
2003, ULIS-DL had created more than 40,000
metadata records, and about 26,000 of those records
are the metadata for the Internet resources publishedby libraries and LIS institutions. A single metadata
record is basically created for a single page in a Web
site, so that one or more metadata records are created
for a single Web site. A single metadata record
includes one or more Subject elements of Simple
Dublin Core, each of which contains a single subject
term. These metadata are provided for users through atext retrieval interface, but no directory style interface
has been built.
A major issue to enhance the usability of
ULIS-DL has been (semi-)automatic creation of adirectory style interface for navigating users toappropriate resources in addition to the text-based
retrieval function. A subject vocabulary is required tocreate the directory interface. However, since theresources of ULIS-DL are collected from the limited
subject domains, we could not find a well-establishedsubject vocabulary or subject classification scheme
appropriate as a subject vocabulary when we started
the service. Therefore, ULIS-DL defined a guideline
for catalogers which very weakly controls descriptionof Subject elements but it does not give awell-controlled subject vocabulary for the Subject
elements.
2.2 Development of Core Subject Vocabulary for
ULIS-DL
Based on these experiences, we have developed asmall subject vocabulary in order to build a directory

style interface for ULIS-DL which shows subject
terms sorted in hierarchical order, and a list ofresources associated to every subject term. A
preliminary evaluation of the Subject element values
showed that there are more than 15,000 distinct text
strings in the raw metadata, which includes
typographicalerrors,inappropriate
useofupper/lower case letters and so on. We also found thata set of subject terms assigned to a page in a Web site
significantly overlaps to that of other pages in thesame site and that the divergence of the number of
metadata records per site is significantly large.
After having the raw metadata normalized, we
followed the following steps to create a core subject
vocabulary.
(1) Removal of overlapped subject terms in a single
site: In order to avoid over-counting of a term thatfrequently appears but only in one or a few sites,
we merged metadata records of each single Web
site into one record and got a merged set of subject
records.
(2) RemovalofCreator/Contributor/Publisher
element values: We created a set of subject terms
by extracting distinct text strings from Subject
elements of the set of merged metadata records. At
this phase, Subject element values of a site which
are the same as a value of Publisher, Creator, orContributor elements of the site were excluded
from the set because values of these elements areinappropriate as a subject term. This set createdthrough this process is called the primary subject
term set.
(3) Creation of candidates of the core subject
vocabulary: We created a set of subject terms fromthe primary set by extracting terms that appear N ormore times (N>1) in the set of merged metadata
records. This set is called a candidate term set,
CTS-N.
(4) Evaluation of the candidate sets: We created
CTS-2, 3, 4 and 5 and evaluated the ratio ofcoverage of the set over the whole metadata. We
used the “uncoverage” ratio, which is defined as
the ratio between a number of metadata records that
do not have any of the core subject terms and thetotal number of metadata records, in order toevaluate cost-effectiveness of CTS-N. Table 1
shows CTS-N and its uncoverage ratio (N=2, 3, 4,
5).
We chose CTS-5 as the core subject vocabulary inthis study because it covers approximately 90% of thetotal records, and also because we considered its sizeas the most reasonable to manually organize thesubject vocabulary terms, i.e. classifying the terms
and defining relationships between the terms.
We classified the CTS-5 terms into eightcategories, which are (1) Web terms, e.g., links, (2)Library terms, e.g. OPAC, (3) Organization andfacility information, e.g. floor guide and access, (4)Type of libraries, e.g. university library and public
library, (5) Organization names and service names,(6) Place names, (7) General subject terms, and (8)Reference tools, e.g. dictionaries, thesauri. Then, weclassified terms in these categories into detailed
categories up to the third level to constitute ahierarchical structure of subject terms. We assigned aproper subject term to each node of the tree. Everysubject term of CTS-5 was associated to a leaf node
as an occurrence term in the metadata. We encoded
the tree structure in OWL. A few example
descriptions is presented in Figure 1.

Table 1. Coverage of Candidate Term Sets
Total number of metadata records = 26358
Total number of Subject element values in the
primary term set = 28797
Total number of Subject element values
excluding Publisher/Creator/Contributor
values = 26107
number of
Subject
terms

number of
excludedrecords

Uncoverage
ratio

CTS-2

3979

1519

6%

CTS-3

2045

2083

8%

CTS-4

1366

2590

10%

CTS-5

1025

2801

11%

3. Development of CommunityOriented Subject Vocabularies

3.1 Lessons Learned from Preceding Study:
Internet Public Library – Asia
Internet Public Library – Asia (IPL-Asia) is a
project to collect Internet resources usefulfrom the viewpoint of public libraries
published in Chinese, Japanese and Korean(CJK) languages and to provide information
about the resources in all of the CJK
languages[4][9]. As part of this project, wecollected subject terms to classify the resources
published for children. We found that a subject
vocabulary designed for children’s resources is
indispensable to classify the resources and tobuild a directory style navigational interface inaddition to the subject vocabularies widelyused in the library communities, e.g.,
Universal Decimal Classification (UDC) andNippon Decimal Classification (NDC). This isbecause the domain of the resources is narrow
and the subjects are community-specific, thesubject terms of those well-establishedvocabularies are difficult for children tounderstand, and appropriate terms should bechosen to express the subjects in accordancewith the age levels of the children, e.g., first to
third graders, fourth to sixth graders, seventh
to ninth graders, and higher to general public.
Moreover, we learned that maintenance of thesubject vocabularies by a community (orcommunities), and that re-usability andinteroperability of the vocabularies amongneighboring communities are crucial sincecosts for creation and long-term use of the
vocabularies are not negligible.
Based on the experiences in IPL-Asia, we havedefined the following guidelines to build subject
vocabularies for community-oriented metadata.
(1) Create a core subject vocabulary which should
be a reasonably small set of subject terms.
(2) Create subject vocabularies by tailoring the core
vocabulary
andassociating
appropriate
expressions to every subject term in order to<uo:Subject rdf:ID="uo_1"
uo:print_name="Library Terms"><uo:sub_subject_id rdf:resource="#uo_2"/><uo:sub_subject_id rdf:resource="#uo_9"/></uo:Subject><uo:Subject rdf:ID="uo_2"
uo:print_name="Resource Search"><uo:super_subject_id rdf:resource="#uo_1"/><uo:sub_subject_id rdf:resource="#uo_3"/><uo:sub_subject_id rdf:resource="#uo_7"/></uo:Subject><uo:Subject rdf:ID="uo_3" uo:print_name="opac"><uo:super_subject_id rdf:resource="#uo_2"/><uo:sub_subject_id rdf:resource="#uo_4"/><uo:sub_subject_id rdf:resource="#uo_5"/><uo:sub_subject_id rdf:resource="#uo_6"/></uo:Subject><uo:Subject rdf:ID="uo_4" uo:print_name="OPAC"><uo:super_subject_id rdf:resource="#uo_3"/></uo:Subject><uo:Subject rdf:ID="uo_5"
uo:print_name="Online Public Access Catalog"><uo:Subject rdf:ID="uo_9"
uo:print_name="Digital Library"><uo:super_subject_id rdf:resource="#uo_1"/><uo:sub_subject_id rdf:resource="#uo_10"/></uo:Subject>
Library Terms
Resource Search
opac“OPAC”“Online Public
Access Catalog”

Digital Library

Figure 1. Subject terms described in OWL and
Category Structure

present the subject terms in accordance with theproperties of users, i.e., age range and language.
(3) Encode the vocabularies in an ontology
description language such as XML Topic Mapsand OWL. This encoding is essential not only for
automatic creation of subject directories frommetadata records but also for interoperability ofthe subject vocabularies and for long-term
maintenance of the subject vocabularies.
3.2 Development of Community-Oriented Subject
Vocabularies
Based on the above guidelines, we have built a
subject vocabulary for the Internet resources
collected by Digital Okayama Dai-Hyakka (DODH).
The vocabulary, which is called Okayama Kids
Vocabulary (OKV) in this paper, is designed
primarily for children. In parallel to OKV, theprefecture of Okayama has built a subject vocabulary
for classification of the Internet resources publishedby the government offices of the prefecture. Both ofthese subject vocabularies are designed to be simple
because the subject terms will be used by the generalpublic and children, and because metadata will be
produced by non-professional catalogers. In addition
to these vocabularies, NDC is used by librarians.
As shown in Figure 2, each of the subject termsof OKV has four presentation labels chosen inaccordance with user ages, i.e. first to third graders(junior level of elementary school), fourth to six
graders (senior level of elementary school), seventh
to ninth graders (junior high school level), and eighthor higher graders (high school to general public).
Presentation labels for the youngest age group has tobe readable and understandable for children of thatage, so that we can use only Hiragana, Katakana anda limited set of Kanji (Chinese characters)2 and wehave to re-phrase subject terms into plain words orphrases to make it easier for children to understand.
For higher graders of elementary schools, we also use
easier words and phrases for presentation labels, andwe add pronunciation scripts3 to the subject terms
expressed. Presentation labels designed for juniorhigh school students are almost the same as those forgeneral public but some of them are re-phrased and2
Hiragana and Katakana are syllabic
characters. First graders first learn Hiragana,then Katakana and a very limited set of Kanji.
Students continue learning Kanji throughelementary and junior high schools.
3 In Japanese, every single Kanji character(Chinese character) has one or morepronunciations. Pronunciation of a Kanji
basically depends on a word in which the Kanji
is included but there are many exceptions.
Pronunciation scripts, or Yomi in Japanese,
helps children understand the subject terms.

there is additional pronunciation information.
OKV has eight major subject term groups. Eachof the major groups has sub-groups of terms. As ofJanuary 2004, OKV has approximately 280 subject
terms. Each subject term is included in one or moregroups. The subject terms are collected from several
major portal sites dedicated to resources for children
and tailored them in accordance with therequirements of OKV. For example, some terms are
specific to activities and events at schools andregional
communities
suchas
excursion,commencements, entrance examinations, and so on.
The metadata schema of DODH is based on the
Simple Dublin Core. OKV is to be used to create
directories from DODH metadata and search aids.
“としょかん”
juniorelementary schoolpresentation
labels

図書館（トショカン）”seniorelementary school“Library”“図書館”
junior high schoola subject term

“図書館”
high school togeneral public

Figure 2. A subject term withmultiple presentation labels
3.3.
Discussionon
Subject
Vocabulary
MaintenanceIn our preliminary study, we have built the subject
term vocabulary for IPL-Asia using XML Topic
Maps in which each subject term is defined as a topic
and associated with multiple presentation labels in
the CJK languages. We applied the multi-lingual
subject vocabulary to the IPL-Asia metadata and the
DODH metadata in order to build subject-based
directories of the resources. This experimental study,
which is a straightforward approach, has shown thefeasibility to build a user interface that has multiple
presentation modes.
From this study, we have learned that ontology
description languages such as XML Topic Maps and
OWL are useful not only for encoding the vocabulary
in a machine understandable form but also for
maintaining the vocabulary for long term. Vocabulary
maintenance is a crucial issue even if OKV is a small
set of terms since it evolves over time, for example,
evolution of subject terms and subject groups, andupdate of presentation labels. XML-based encoding
is not a panacea but will help to decrease the cost of
maintenance.
We consider that a metadata schema registry,
which stores reference descriptions of metadata
schema elements and provides them to users via theInternet, is a useful tool to store and maintain thesubject vocabularies. The metadata schema registry
has a function to register multiple labels in different
languages associated with a single term.

4. A Conceptual Model of Metadata andMetadata Schema for Interoperability
4.1 Basic Concepts of Dublin Core and a Model ofMetadata
4.1.1 Simple Dublin Core and Qualified Dublin
Core
Dublin Core has been defined as a set of fifteen
elements for cross-domain resource discovery. The
use of these fifteen elements for metadata records,
with no additional qualifiers, and with only plain-text
strings as values, is known as “Simple Dublin Core”.
By design, any of the fifteen elements is optional andrepeatable. This set has been approved as aninternational standard-ISO 15836. “Qualified Dublin
Core”, in contrast, uses the elements together withqualifiers that increase the richness and precision ofdescription. Qualified DC has two types of qualifiers– element refinement and encoding schemes.
DCMES is a stable but not a closed set. DCMES
evolves in accordance with requirements to express
resource properties and value-types which are notexpressible using existing ones. The following
sections show underlying key concepts of Dublin
Core[10]. The article reported by Andy Powell showsan abstract model from an architectural viewpoint[5].
4.1.2 Warwick Framework – Basic Framework for
Extensibility
Since the Internet is a very diversified environment, it
is useless to assume that a single metadata element
set will meet the needs of all domains and purposes.
It is also impractical to develop metadata sets
application by application: the result would be
expensive and chaotic, and interoperability would be
non-existent. On the other hand, it is desirable forapplication developers to use established metadata
schemas and adopt them in accordance with local
requirements. The Warwick Framework, a conceptualmodel that resulted from the 2nd Dublin Core
Workshop in 1996, gave an early expression to thenotion of metadata as modular components that may
come from more than one metadata schema[3]. In
this model, a metadata instance is expressed as acontainer which contains one or more packages, eachof which is expressed in a given metadata schema.
The Resource Description Framework (RDF)
provided a practical realization of many of the ideasof the Warwick Framework.
The Warwick Framework is important as amodel for modular metadata on the Internet. No
single metadata schema is sufficient to allapplications. Rather, it is necessary to adopt
appropriate elements from various schemas into a given domain or application:- Title, Creator and Description might be mandated
but others are optional,- Use only Title, Creator, Description, Date andLanguage elements,- Use the 15 elements of Simple DC and someelements from other metadata sets such as theIEEE Learning Object Metadata (IEEE LOM), andso forth.
These
requirements
canbedefinedindependently of the vocabulary definitions.
Description of this application-specific syntactic
feature is called an application profile. Any
application can have its own application profile,which specifies a set of metadata vocabulary terms
used in the application as well as syntactic or
structural features of the particular application.
Figure 3 shows a model of application profiles. The
vocabulary terms could be borrowed from one ormore source schemas. More importantly, theapplication profile could be used to define a mapping
between the application’s scheme to a global
scheme(s), which is crucial for interoperability.

accordance with the functional requirements of an
application. Application Profiles described in section
4.1.4, which provide a framework to adopt one ormore element sets in accordance with an application,
could be also considered as a realization of the
Warwick Framework.
4.1.3 The Dumb-Down Principle as a Basis forInteroperability
The Dumb-Down principle gives a guideline for
qualification. The Dumb-Down principle suggeststhat a value of a qualified element has to beconsistent as a value of the element without any
qualification. For example, given the following
qualified values:(1) (Element
Refinement)
Date
Accepted:“2002-12-11”, and(2) (Encoding Scheme) Language: “en” encoded in
RFC 1766.
Then, assuming that the qualifications in the above
examples, Accepted, RFC 1766 and the component
names of the value structure (i.e., name, affiliationand contact) are removed. The values of example 1
and 2, “2002-12-11” and “en” are still consistent with
their elements after the removal.
Dumbing-down is a crucial function for
metadata interoperability in the global community
since local communities can extend their schemas inaccordance with their requirements, and at the sametime they can also keep their metadata interoperablewith other metadata communities.

4.2 A Conceptual Model of Metadata Schema forInteroperability
A metadata schema defined for an application iscomposed of three layers:(1) Layer 1 - Semantic Definition Layer: Definitionof terms used in the schema. In other words,
definition of metadata vocabulary, i.e. metadata
element set. In general, two types of metadata
terms are included in the metadata vocabulary –property vocabulary and value vocabulary[1]. A
property vocabulary, or in other words element
vocabulary, is a set of property terms, for example,
elements and element refinement qualifiers of
DCMES. A value vocabulary is a set of value terms,
for example, encoding schemes. Definition of eachterm should primarily include a primary name and4.1.4 Application Profiles
Dublin Core Metadata defines the vocabulary of
metadata, i.e., terms and their meanings, but ingeneral does not specify the encoding or syntactic
characteristics. An exception is the feature includedin Simple DC that is “Any of the 15 elements is
optional and repeatable.” Local applications, however,
may have domain specific requirements appropriate<rdf:Description about=”foo”><mv1:A>an example.</mv1:A><mv2:X>bar</mv2:X>...

<meta name=”mv1:A”
content=”an example”><meta name=”mv2:X”
content=”bar”>

Description in asyntax defined in
an application...

termA:
Mandatory

termA

termC:
Optional
Repeatable

termB

termC

Metadata Vocabulary 1(Metadata Element Set)

termX:
Mandatory
Repeatable

termX

termZ:
Mandatory
if applicable

termY

Metadata Vocabulary 2(Metadata Element Set)

Figure 3. Concept of Application Profile

Application Profile:Terms used in an
application andstructural
constraints
termZ

its meaning. Thus, a vocabulary definition gives
the semantic basis of a metadata schema.
(2) Layer 2 - Structural Constraints Definition
Layer: Definition of syntactic features which does
not depend on any particular implementation
scheme. A set of terms used in the schema andstructural constraints applied to each term should
be included in a definition. Application profiles are
given in this layer.
(3) Layer 3 - Implementation Dependent Syntax
Definition Layer: Definition of syntax of metadata
in an implementation, for example, metadata
description syntax in HTML, XML, and RDF.
In addition to these definitions, each application
schema developer would provide guidelines forcreating metadata. Figure 4 illustrates relationships
among schemas based on the conceptual framework.
The layer 1 of Figure 4 provides definition of
metadata elements and qualifiers of a metadata
schema. On the other hand, there are controlled value
vocabularies and value encoding schemes which aredefined neutrally to any specific metadata schema,e.g., DDC for expressing subjects and ISO 8601 forencoding dates. Every single term of a controlledvalue vocabulary is given its definition as well, e.g. a
decimal number and its associated label(s).
4.3 Metadata Schema Registry
A metadata schema registry stores andprovides metadata schemas not only forhuman but also machines. A metadata schema
registry is a key software tool to enhanceinteroperabilityofmetadata
schemasexpressed in all layers. For example, the DCMI
metadata schema registry[2][6] which provides
reference descriptions of DCMI terms isdesigned primarily for layer 1. Every DCMI
term is expressed in RDF Schema. The DCMI
registry provides the reference descriptionstranslated into more than 20 languages.
Metadata schema registries are useful to store
and provide all types of metadata vocabularies,
i.e., application profiles, subject terms andother vocabularies.
There are some issues that are recognized
important for future. For example, long term
maintenance of metadata vocabularies is an
important issue for metadata interoperability
over time[8]. Interoperability of metadata
schemas are obviously important for metadata
interoperability. Re-usability of metadata
schemas is important to decrease the cost ofschema development and interoperability.
Metadata registries have large potential tosolve these issues.

5. Discussion – Creation, Maintenanceand Interoperability of CommunityOriented Metadata Vocabularies
This paper has presented two case studies of
metadata-centric services, both of which are based on
Simple Dublin Core. Some lessons we learned fromthe case studies are as follows:(1) Subjects of Web resources in a specific domain
can be covered by a reasonably small set of subject
terms even though the subject terms are very
weakly controlled within the metadata creation
process. On the other hand, the set of subject terms
includes domain-specific subject terms which are
not covered by large general-purpose subject
vocabularies.
(2) A scheme to associate different presentation labels
to a single term in a subject vocabulary is crucial
not only to enhance usability of user interfaces inaccordance with users but also to enhancemaintainability of the vocabulary. XML-based
vocabulary description is useful in this respect.
(3) Communities need subject vocabularies which arebuilt in accordance with their domain, goal andlanguages. However, maintainability of the subject
vocabularies is a crucial issue for the communities
to build and maintain metadata for long term. From
this viewpoint, a reasonably small vocabulary
designed based on community requirements isadvantageous, and software tools designed forLayer 3XML
implementationin an XMLAn Oracle
implementation

RDF
implementation

Layer 2

DCMI Library
Application
ProfileOpen Archives
Initiative
SchemaIPL Asia
SchemaLayer 1DCMES
(Elements andQualifers)

IEEE-LOM
elements

ULIS
Core
SchemaULIS element
extension

Figure 4. Layered Model of Metadatavocabulary maintenance are crucial to enhance theusability and reliability of the vocabulary.
Library catalogs, which are a typical metadata,
have been created by professionals for high quality
description of resources. Library community has
developed a rich set of metadata vocabularies which
are utilized well not only by libraries but also by
library users, publishers and related communities.
However, the conventional business model does notalways work well in the Internet environment where
huge number of diverse resources are published andused by divergent communities. Any community,
which may be regional or domain specific, would be
able to develop metadata vocabularies in accordancewith their requirements, but maintenance of the
vocabularies for long period of time seems to be amajor and practical barrier for the community todevelop the vocabularies. From this viewpoint, weconsider that it is important to keep the vocabularies
simple and small, and that vocabulary maintenancesoftware has an important role.
The Internet has realized a global infrastructure
to access resources regardless of geographicaldistance. However, community oriented information
environment has not been realized well. Metadata
schema designed for communities is a crucialcomponent to realize the community oriented
information environment. On one hand, communities
need metadata schemas designed for themselves, buton the other hand, interoperability and reusability of
metadata and metadata schema with othercommunities are crucial. Thus, it is required to satisfy
two contradictory requirements, i.e. specialization vs.
generalization.

6. Concluding Remarks
From our experiences in IPL-Asia and ULIS-DL, wehave learned that these systems need subject
vocabularies designed for them in addition to wellestablished subject vocabularies such as UDC and
NDC. The subject vocabularies created for DODH,
which is an ongoing project hosted by the Okayama
Prefectural Culture Center (OPCC), is being used byparticipating catalogers at OPCC and relatedorganizations. We will continue our study to evaluate
the usability and validity of the vocabularies and tobuild technologies to support maintenance of the
vocabularies.
Community-oriented information environments
need to satisfy the contradictory requirements. We
believe that metadata schema registries and metadata
schemas encoded in an XML-based ontology
description scheme are key technologies to satisfy therequirements. We also consider that the model
presented in this paper provides some basic
guidelines to find solutions for the contradictory
requirements.

Acknowledgments
We would like to express our thanks to Drs. Stuart
Weibel, Thomas Baker, Koichi Tabata, Tetsuo
Sakaguchi, Atsuyuki Morishima for their support. We
would like to thank Huishan Jiang and Akiko Shingai
for their contribution to the development of thesoftware tools. We would like to express our special
thanks to Infocom Corporation for their support toour collaborative research and development activities
between University of Tsukuba and the Okayama
Prefectural Cultural Center.

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