Towards Ontology Development Based on Relational Database

Integrated Intelligent Research (IIR) International Journal of Web Technology
Volume: 01 Issue: 02 December 2012 Page No.57-60
ISSN: 2278-2389
57
Towards Ontology Development Based on
Relational Database
L. Ravi, N .Sivaranjini
Department of Computer Science, Sacred Heart College (Autonomous), Tirupattur.
Email:raviatshc@yahoo.com, ssk.siva4@gmail.com
Abstract- Ontology is defined as the formal explicit specification
of a shared conceptualization. It has been widely used in almost
all fields especially artificial intelligence, data mining, and
semantic web etc. It is constructed using various set of resources.
Now it has become a very important task to improve the
efficiency of ontology construction. In order to improve the
efficiency, need an automated method of building ontology from
database resource. Since manual construction is found to be
erroneous and not up to the expectation, automatic construction
of ontology from database is innovated. Then the construction
rules for ontology building from relational data sources are put
forward. Finally, ontology for “automated building of ontology
from relational data sources” has been implemented.
Keywords: Schema, Generation, Ontology, Database
I. INTRODUCTION
Ontology provides a shared and reusable piece of knowledge
about a specific domain, and has been applied in many fields,
such as Semantic Web, e-commerce and information retrieval,
etc. However, building ontology by hand is a very hard and
error-prone task. Loading ontology from existing resources is a
good solution. Because relational database is widely used for
storing data and OWL is the latest standard recommended by
W3C. This paper proposes an approach of loading OWL
ontology from data in relational database. Compared with
existing methods, the approach can acquire ontology from
relational database automatically by using a group of learning
rules instead of using a middle model. In addition, it can obtain
OWL ontology, including the classes, properties, properties
characteristics, cardinality and instances, while none of existing
methods can acquires all of them. Thus an automatic generation
of ontology from database is designed in this paper.The main aim
of this paper is to build ontology automatically using the
relational database resources to improve the efficiency is
proposed to achieve efficient interoperability of information
systems. This paper includes the related work of mappings
between relational databases and building OWL ontology based
on the relational database. The relational schema is mapped to
ontology through the analysis of the relations among primary
key, attributes. Then, the relational data is mapped to ontology
instances. Since the semantic in relational model is very limited,
these methods can be used only to build lightweight ontology. In
this work, the mapping rules between relational database
elements and ontology are proposed based on existing ontology
construction method. Manually correcting the logical
inconsistencies in the first version of the OWL ontology; making
use of foundational ontologies. The conversion of these
databases into RDF/OWL format is an important step towards
realizing the benefits of Semantic Web research. Based on this
manually created basic ontology, the data from the databases
were then automatically converted to OWL using programs
written in Java and Python. The automated export scripts
extended the manually created basic ontology through the
creation of subclasses, OWL property restrictions and
individuals. The resulting ontologies show no clearly
distinguishable division between a schema and data. This
document describes representation of the databases in Resource
Description Framework (RDF) and Web Ontology Language
(OWL), and discusses the advantages and disadvantages of these
representations.
II. AUTOMATIC GENERATION OF ONTOLOGY FROM
DATABASE SCHEMAS
Initially a mapping between attributes and database is made. That
mapping process starts by detecting particular cases for
conceptual elements in the database and accordingly converts
database components to the corresponding ontology components.
A. Ontology for Database Design
The method used to develop the ontology is outlined and the
components and representation issues discussed. The research is
intended to use existing libraries of ontology’s as they are
developed. As mentioned above, there has been much call for the
development of ontology’s for different application domains that
can be shared amongst different applications and interest groups.
Although the actual development of ontology in are not the focus
of this research, the following outlines the procedure followed
for the manual, but systematic, development of the ontologes
used in this research.
B. Components and Development
The main components of ontologies are terms, relationships, and
axioms. The relationships that typically appear in an ontology are
subclass-of (is_a), instance-of, synonym, and related-to. This
research extends these main concepts to include domain
relationships that capture additional constraints needed for
database design and which represent, to some extent, semantic
integrity constraints. There additional constraints capture various
aspects of a business application.
C. Ontology Components and Representation
In ontology development, concepts or terms are often organized
into taxonomies with binary relationships. Most ontology’s focus
heavily on terms, often organized as a class and subclasses. To a
much lesser extent, instances of terms are included. Representing
and reasoning with these basic components is not enough to
create heavyweight ontology capable of supporting complex
reasoning. Therefore, before implementing ontology, one should

ISSN: 2278-2389
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decide on the application needs in terms of expressiveness and
inference.This research extends the relationship component of
ontology. For conceptual modelling, the basic relationships
(synonym, is_a, and related_to) employed in an ontology are
limited because of their inability to capture domain specific
knowledge (business rules). We model other types of
relationships, which we call domain relationships, the purpose of
which is to define and enforce business rules.
The following four types of domain relationships:
 Pre-requisite
 Mutually-inclusive
 Mutually-exclusive
 Temporal
Figure 1. Partial Auction Domain Ontology
D. Ontology-based approach for Database design
The two primary ways in which an ontology could be used to
improve a design are:
1. Conceptual model generation
2. Conceptual model validation
The role of an ontology is to provide a comprehensive set of
terms, definitions, and relationships for the domain for which a
conceptual model is to be created. Therefore, the first task is to
generate a design “from scratch,” using the terms and
relationships in the ontology as representative of the domain. The
second task is to use the ontology to check for missing terms or
inconsistencies in an existing, or partial, design.
III. IMPLEMENTATION
Most conceptual data models of information systems are created
from scratch, wasting time and resources. Ontology represents
the real-world domain knowledge. So ontology can be reused in
conceptual model building. However ontology engineering is not
mature enough. In this paper the new approach is proposed to
develop Automatic generation of Ontology from Relational
Database (AGOFRD). The ontology can be evaluated, extended
and reused as domain knowledge for other conceptual data
models.
A. AGOFRD Implementation
Initially the structure of AGOFRD can be divided in to three
parts based on the above rules and the construction process of
ontology.
1. Database metadata reading
2. Ontology meta-model construction and
3. Goal ontology generation
B. Database Metadata Reading
A metadata is nothing but the data about a data. So metadata
reading is defined as extraction of data or information from
relational databases to establish a relational database model. In
order to link database with ontology, a tool called “Data master is
used”. This links up with the backend databases and retrieves
information stored in the tables.
C. Ontology Meta Model Construction
By analyzing the relational database metadata model, the
relational database metadata model is converted in to ontology
meta-model. Conversion is done based on the above proposed
rules and definitions. The main content of ontology meta-model
construction is to construct an ontology meta-model Graph
Model, which consists of the set of nodes (defining a node
contains the concept name and property) and the set of edges
(defining an edge as the connection of two concepts).
D. Goal Ontology Generation
Extracting ontology information from above ontology meta-
model, it maps the database data into ontology instances
according to the data conversion steps from relational database to
OWL ontology. Finally, the completed OWL document is
generated. Then, the ontology generated is opened and verified it
in ontology tool Protégé.
E. Method of Mapping Protege to Database
The Ontology is mapped with Relational databases using the tool
called Data Master. Initially a database is created in Microsoft
Access with extension of (*.accdb). Then an ODBC data source
for that particular Database is created.
F. ODBC Data Source Creation
It’s a simple process, in which a data source name and the path
where the database is stored is given as input. Then the path of
data source newly created is given as an input to the Data Master
of protégé 3.3.1. A ODBC Data Source is linked with Data
Master as shown in below figure2.
Figure 2. ODBC Mapping with Ontology
After giving all necessary fields, connect button is pressed. So
this will link with the particular database present in data source
path given and retrieve all the fields present in the database. This
will get mapped automatically based on the above mentioned

ISSN: 2278-2389
59
rules. It has two options basically for ODBC and JDBC. It is left
to user’s choice to use any one of them.
G. Datamaster Plug-in for Importing Schemas from Relational
Databases
There are a variety of ways of describing the schema of a
database in ontology, depending on the requirements of an
application. For example, some applications will only require an
import of the database content without needing a “live”
connection to the database. In other cases, the mapping between
the database structure and the ontology elements is more
important, so that data reside in the database but are accessible to
querying or reasoning through an ontology layer.
IV. SCHEMA STRUCTURE ONTOLOGY
A. Schema Structure Ontology for Protégé-Frames
DataMaster may be used to import a relational database structure
and the table data into Protégé-Frames ontology. The ontology
for describing the database structure (Figure 5.4.) is the same as
the one used by the DataGenie plug-in. All imported database
tables are defined as Protégé classes that are instances of the
Table Metaclass meta-class. Each column of the database table is
represented by a template slot added to the newly created table
classes. The column slots will have data types corresponding to
the SQL types associated to the database columns.
Figure 3. Database schema ontology for Protégé
Frames
If there are foreign keys defined between the database tables, for
each foreign key an instance of the Foreign Key class will be
created that will be used to link the corresponding ontology
classes. It is also possible to import the data from the tables in the
database. For each row in the table an instance of the table class
will be created and the values of the own slots at these instances
will be set with values contained in the table row corresponding
to the table columns. An extra slot of type instance will be
created for each foreign key defined in the table that will point to
the instances corresponding to the referred rows.
B. Schema Structure Ontology for Database tables as OWL
Classes
One of our goals when designing the schema structure ontology
in OWL was to be able to use DL reasoning on it. This means
that certain constructs used in the Frames approach had to be
changed. However, certain combination of import options will
result in OWL Full schema ontology. The Protégé OWL schema
ontology for importing tables as classes is the OWL version of
the previously described ontology for Protégé Frames. There are
only a few differences: The imported classes will not be instance
of a common meta-class, because it would make the ontology
OWL Full. Instead, all the template slots attached to Table
Metaclass in the Frames ontology have been defined as
annotation properties on the imported table classes.The property
and class names from the Frames ontology are using the camel
notation and the space character in the class and property names
have been avoided. E.g., hasForeignKeys instead of Foreign
Keys, Foreign Key instead of Foreign Key, etc.For easier
navigation and performance reasons, we have introduced four
additional object properties attached to the Foreign Key class to
refer the local and referenced table classes as well as the
referring and referred column properties.
C. Schema Structure ontology for database Tables as OWL
Instances using Relational OWL
Another way of representing the structure of a database in OWL
ontology is the approach taken by Relational.OWL. The ontology
used by Relational.OWL is shown in Figure 5.5. It defines four
classes Database, Table, Column and PrimaryKey. The instances
of these classes and their relationships can represent the schema
structure of any relational database. One of the available
configurations of DataMaster is to import the database structure
as instances of the Relational.OWL ontology. However, the
Relational.OWL ontology is OWL Full, because
Relational.OWL defines the representation of the database
column types by using the rdfs:range property on the Column
class, which makes the Column class be an owl:Class and an
rdf:Property at the same time.
IV. RESULTS AND DIRECTIONS
Open the main interface, configure the relevant information
which is needed for database connection, select the save path for
ontology. Then, input the database configuration information,
connect to the database. The OWL ontology is generated using
DataMaster plugin automatically. Database to ontology mapping
correspondences between database components (table, column,
constraint) and ontological components (concept, property).
Database to ontology mapping complex direct data migration
query driven massive dump mapping database to already existing
ontology creating ontology from database mapping definition
mapping definition
Figure 5. Example ontology from relational database

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V. CONCLUSION
Aiming to find a method for automatic generate ontology from
relational database resources to improve the efficiency of
ontology construction. An approach of loading OWL ontology
from data in relational database Construction rules of ontology
elements based on relational database, which are used to generate
ontology concepts, properties, axioms, instances are put
forward.An ontology automatic generation system based on
relational database is designed and implemented according to the
construction rules. Mapping automatically based on the above
mentioned rules based on two options basically for ODBC and
JDBC. This research is an initial step to illustrate how domain
ontology’s, which capture knowledge about specific application
domains, can be used for the creation and validation of entity-
relationship models for conceptual modeling. This research
extends the main concepts of synonym and relations to include
domain relationships that capture additional constraints needed
for database design and which represent, to some extent,
semantic integrity constraints. Ontology generated based on the
construction rules of ontology concepts, instances, properties,
axioms in future ontology is generated based on other attribute
relations.
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