Journal of Software Engineering and Applications, 2012, 5, 687-694
http://dx.doi.org/10.4236/jsea.2012.59082 Published Online September 2012 (http://www.SciRP.org/journal/jsea)
687
Representation of Object-Oriented Database for the
Development of Web Based Application Using Db4o
Vipin Saxena, Ajay Pratap
Department of Computer Science, Babasaheb Bhimrao Ambedkar University, Lucknow, India.
Received June 23rd, 2012; revised July 26th, 2012; accepted August 10th, 2012
ABSTRACT
Impedance mismatch of data flow is the major problem in the relational database when one is using the web based ap-
plication development on the computer system. It effects the development of scalable and reusable web application.
Due to this, the research cost of development and maintenance increases. Therefore the present work is an attempt to-
wards an object-oriented database system by using Db4o to overcome the impedance mismatch problem. In the current
work, the development of web application for Indian Postal Services by using Db4o is demonstrated on dot NET plat-
form. Before developing the application, the authors used a Unified Modeling Language (UML) model in the form of
UML class, sequence and use-case diagrams. The Db4o is used to store the object-oriented database and the perform-
ance of Db4o is observed through several object-oriented queries and corresponding results are demonstrated.
Keywords: RDBMS; OODBMS; Db4o; Web Development; UML
1. Review of Research W o r k
The relational databases are the most common database
management system (DBMS) used as a backend for the
web based application. In the current trend of software
development, many of the software companies are still
using the relational databases but due to impedance mis-
match of data flow and evolution of graphical user inter-
face (GUI), software industries are switching from rela-
tional databases to object-oriented databases. Let us first
describe the important references related to databases.
Elmasri and Navathe [1] have presented a clear explana-
tion of theory and design, broad coverage of models and
real systems, and an up-to-date introduction to modern
database technologies results with a leading introduction
to database systems. Silberschatz et al. [2] have dis-
cussed the inner working of database system and also
discussed about few commercial databases as well as
open source database systems. Paterson et al. [3] have
described to configure the Db4o, querying and managing
objects, performing transactions, and replicating data.
Db4o is highly reliable and scalable, which cuts down on
development time by smoothly integrating into the sys-
tem, cutting out the costly object-relational mapping
typical for larger applications. Db4o developers commu-
nity [4] present various blogs and forums related to ob-
ject-oriented database system such as Db4o, Versant Ob-
ject Database, Versant JPA, ODBMS.ORG, which helps
to get deep understanding on various topics. In [5],
Rosenberger made effort to store all objects manually in
SQL and has took up half time of total development time
and today it is the most well known brand in the niche
category “object databases”. A big RDBMS machine is
oversized for a cell phone. In this case, a tight integration
between the application and the database are helpful to
achieve top performance. Db4o is also used for caching
in near real-time environments when application models
are complex, such as in the financial sector, for trading
applications.
Rădulescu [6] has given a brief look about SQL tech-
nology and demonstrated its limitations on persistence
feature of an object-oriented model and also discussed
the principles and concepts of Db4o and its implementa-
tion on dot NET platform. Danturthi [7] has described a
comparative study between the three different methods of
data access: SQL Server 2005 with stored procedure,
LINQ to SQL and Db4o. Db4o solves the problem of
impedance mismatch and making the development of
database model much simpler and similar to the applica-
tion domain model. Liaw et al. [8] have discussed a three
tier web based application which can be developed for
taking advantage of an object-oriented database instead
of using ADO.NET or traditional relational database.
Bernardi et al. [9] have presented the validation and the
performance evaluation of systems with the help of UML
sequence diagrams and state charts. They proposed an
automatic translation of state charts and sequence dia-

Representation of Object-Oriented Database for the Development of Web Based Application Using Db4o 688
Grams into generalized stochastic petri nets based on the
abstract syntax of the UML collaborations and of the
state machines packages.
Rumbaugh et al. [10] completely described UML
concepts, including major revisions to sequence diagrams,
activity models, state machines, components, internal
structure of classes and components, and profiles. Umoh
et al. [11] have focused on creating a UML structure by
specifying the use-case, classes, and activities in the cli-
ent-server application to design a web-based object-ori-
ented database management system (OODBMS). A
working prototype of the system on three-tier client
server architecture is discussed in this paper. Chaurasia
and Saxena [12] have also introduced a model design
through UML for a mobile based electricity bill deposit
system. A real case study of Uttar Pradesh Electricity
Bill deposit System is considered. In [13], Tagliati and
Caloro have discussed the application of UML for the
analysis of dynamic words. Mangala [14] also described
about the need of ASP.NET and designed the program-
ming model through ASP.NET, which is a completely
re-engineered and enhanced technology that offers much,
much more than traditional ASP and can increase pro-
ductivity significantly.
2. Background
2.1. Object-Oriented Database
Evolution of internet and extranet has increased the us-
age of web-based technology and the companies have
shown their interest in object-oriented database man-
agement system (OODBMS) to handle the complex data.
OODBMS is fusion of two technologies: object-oriented
system and database management system. New applica-
tions require data persistence, transaction, authorization,
distribution, buffering and data scalability associated
with the database system, which is fulfilled by the
OODBMS. The term object-oriented database system
first appeared in 1985 and 2004 was second growth pe-
riod when open source database system such as Db4o and
DTS/SI emerged, which was affordable and easy to use.
Db4o (database for objects) is an open sourced bi-li-
censed software (General Public License and Commer-
cial), written in both java and .NET and can run on any
operating system that supports java or .NET. It stores the
objects directly without changing their characteristics or
crops them to fit in a table of relational data model. The
db4o project was started in 2000 by Carl Rosenberger
and it was commercially launched in year 2004 by
Db4objects Inc but in 2008 it was brought by Versant
Corporation.
2.2. Unified Modeling Language
The Unified Modeling Language (UML) which is a very
dominant modeling graphical language for specifying,
constructing, presenting and documenting the artifacts of
software system. It is a collection of best engineering
practices that have successful in the modeling for a
design of a huge and complex systems. Modeling
through Unified Modeling language has three categories:
Class Model, State Model and Interaction Model. The
class modeling is done with the help of object diagram
and class diagram. The state model is done, using state
diagram and the Interaction modeling is done with the
help of activity diagram, use-case diagram and sequence
diagram. The main task of the UML is to create a simple,
well documented and easy to understand software model
for the people.
2.3. Web Based Applications
Web based applications are classified into two major
categories: static web applications and dynamic web ap-
plications. Static web applications are those applications,
where the elements comprising the web application are
static HTML pages. In this environment, the end user can
not interact or modify the application behaviour. On the
other hand the dynamic web applications have capability
to interact or modify with the application behaviour. The
end user gives input and it can be parsed both at the cli-
ent end or server end. Client side scripts the language by
using VB Script and Java Script which are required to
parse and interact according to the client input. Using the
client side scripting language reduces the traffic of net-
work and also increases the throughput of web based
applications.
Server-side scripting is a web server technology and
the programs that are executed on the server to generate
dynamic web pages. The languages used for these tasks
are normal programming languages with special libra-
ries/packages for server side scripting like ASP, C via
CGI (*.c, *.csp), PHP (*.php), ASP.NET (*.aspx), Java
via java server pages (*.jsp).
The clients use web browsing software to interact with
the web server. In ASP.NET when any *.aspx file is re-
quested then the request is send to the Internet Informa-
tion Server (IIS), which is send to .NET engine. The
NET engine parses the client request and converts it to
HTML, which is returned to IIS. Finally, IIS returns the
HTML to the web browser. Hyper text transfer protocol
(HTTP) and file transfer protocol (FTP) are used to deal
with the client request and server responses.
3. Architecture of Web Based Application
The structure of the web based application can be single-
tiered, two-tiered or three-tiered. Here, authors are using
the three-tiered architecture as shown below in Figure 1,
which contains the presentation layer, application layer

Representation of Object-Oriented Database for the Development of Web Based Application Using Db4o 689
Windows XP (SP1) operating system. An object-oriented
database management system Db4o 7.14 is used as a
back-end. Db4o is an open source OODBMS, which is
freely available and it can be downloaded from: http://
community.versant.com/ Downloads. aspx.
Using Web Browser
Using Web Server/ IIS
Database Server
PRESENTATION LAYER
APPLICATION LAYER
DATA LAYER
The software and hardware requirements are described
above in the Table 1.
Installation of Db4o database is done with the help of
an object browser known as Object Manager Enterprise
(OME). After installing it as a plug-in of Ms-Visual Stu-
dio 2008, one can get a sub option of object Manager
Enterprise in tools option of menu bar. After the comple-
tion of installation, new tools are added in the window
and it is shown in Figure 2.
Figure 1. Three tiered web architecture.
To create a new web application choose “New Pro-
ject” from the file menu, in the pop up window select
“web” from the visual c# project type. Then choose
“ASP.NET Web Application” from the template sub
window as shown in Figure 3. We have to add Db4-
objects.Db4o.dll files to the references of project, which
is freely available and the process is shown in the Fig-
ures 3 and 4.
and data layer.
Presentation of data and GUI environments are pro-
vided to the user with the help of presentation layer. All
the rules for the accessing of data and business logic is
presented in the application layer. The data layer handles
the requests from the application layer. Figure 1 repre-
sents the three tier application architecture of web based
applications.
4. Implementation 4.1. Sample Queries for Indian Post Office
Database
The project has been developed in Microsoft visual stu-
dio 2008 IDE with ASP.NET using C# on Microsoft After completing these tasks, one can store new objects
Figure 2. Installation of Db4o.

Representation of Object-Oriented Database for the Development of Web Based Application Using Db4o 690
Figure 3. Starting Db4o web project.
Table 1. Software and hardware requirement table.
Hardware Requirements
Min Recommended Used
Processor 400 MHz 1 GHz Intel Pentium Dual CPU 2.20 GHz
RAM 96 MB 256 MB 0.99 GB
Software Requirements
Operating System Microsoft Windows XP Professional (Version 2002) SP1
Microsoft Visual Studio 2008 (Version 9.0.210222)
Microsoft .NET Framework (Version 3.5)
Application Softwares
Db4o version 7.12
in Db4o. Object files are the class objects with properties.
Here we have four major classes, which are User,
Scheme Database, Office Database and SalesRecord. The
User class has three sub-classes, which are Admin, Em-
ployee and Customer. The User object file is created by
creating a class in C# with all its properties. These
properties are converted as a database object file for
Db4o. The code for object storage mechanism in Db4o is
given below and also shown in the Figure 5.
Code for storing User Class in C# for Db4o:
class User
{
private int UID;
private string Name;
private string Address;
private string MobNumber;
public User (int UID, string Name, string Address,
string MobNumber)
{
this.UID=UID;
this.Name=Name;
this.Address=Address;
this.MobNumber=MobNumber;
}
public User()
{}
User user=new User(1001, "ajay", "Lucknow",
"9936189152");
try{
IObjectContainer
db=Db4oFactory.OpenFile("User.yap");
db.Store(User);
db.Commit();
}
Three methods used for qurying the objects in Db4o e

Representation of Object-Oriented Database for the Development of Web Based Application Using Db4o 691
Figure 4. Adding Db4objects.Db4o.dll file.
Figure 5. Storing objects in C# for Db4o.
are: Query By Example (QBE), Simple Object Data Ac-
cess (SODA) and Native Queries (NQ). Authors have
used native query for the querying purpose in this paper.
The query is expressed as predicate in .NET language as
the object template. The problem of impedance mismatch
is completely removed when one can use native query in
Db4o. Code for native query is given below:
try {
IObjectContainer
db=Db4oFactory.OpenFile("User.yap");
IList<Class1>result= db.Query<Class1>(delegate(Class1
obj){
return obj.Name = "ajay" && obj.Address
=="Saharanpur";}); PrintResults(userList);
}
Figure 6 represents a use case diagram for the Cus-

Representation of Object-Oriented Database for the Development of Web Based Application Using Db4o 692
tomer, which has three use-cases: Search Schemes,
Validate Password and Make Payment. Specilization of
general use-case “Search Scheme” is done into two child
use-cases “Search by Category” and “Search by Amount
Limit”. Similarly, specilization of general use case
“Make Payment” is done in two specialized child use
cases “Credit Card Mode” and “Net Banking Mode”.
Figure 7 represents a use case diagram for the Admin,
which has five use cases: Search Scheme, Add Scheme,
Validate Password, Make Trade, Add Emp & Branches.
Generalization of use-case “Add Scheme” is done into
two child use-cases “Add Banking Services” and “Add
Non-Banking Services”. Similarly, use case “Make Trade”
has two specialized child use-cases “Credit Card Mode”
and “Net Banking Mode”.
4.2. UML Sequence Diagram
Sequence diagram shown in Figure 8 has five objects
Admin, Scheme_Database, Office_Database, Business_
Layer and DataAccess_Layer. In this diagram, the Ad-
min adds a new scheme at Scheme_Database.
The request is being sent at Business Layer and
PerformUpdate (SID, Qty) operation is performed at
DataAccess Layer. The Admin can also add a new em-
ployees and branches in office database. After that the
request is being sent at Business Layer and Perform
Update( ) operation is performed at DataAccess Layer.
The Admin can perform queries for the available
schemes in the Scheme_Database. The ComputeQuery( )
operation is performed at Business_Layer and the Re-
trieveResult( ) operation is performed at DataAccess_
Layer. Finally, the result is passed to the Admin.
4.3. UML Class Diagram
The UML class diagram shows the static structural beha-
viour of the system, in which attributes and operations
are designed for the complete system. Figure 9 re-
presents the class diagram of the online post office
Figure 6. UML use-case diagram for administrator.
Figure 7. UML use-case diagram for Customer.

Representation of Object-Oriented Database for the Development of Web Based Application Using Db4o 693
Figure 8. UML sequence diagram for administrator.
Figure 9. UML class diagram for the application.

Representation of Object-Oriented Database for the Development of Web Based Application Using Db4o 694
system. The class diagram has nine persistent classes,
which are User, Admin, Employee, Customer, Office_
Database, Scheme_Database, Branch, Scheme and Sales
Report and one transient class Control. Classes are
connected to each other by various relationships with
their multiplicities as shown in the diagram and the
transient class Control is used to manage all persistent
classes. Admin, Employee and Customer are inherited
from non-abstract class User. Class Office_Database
consists of many branches and many employees. Aggre-
gation between the classes Office_Database, Branches
and Employees are shown in the class diagram. Scheme_
Database also consists various types of schemes. So,
aggragation is also shown between class Scheme_Data-
base and Scheme.
5. Conclusion
Major web applications are being developed using rela-
tional database management system (RDBMS) but
enough time is consumed for relating the object model
of .NET and database model. Object-oriented database
system (OODBMS) is an alternative of RDBMS, which
can be verified efficiently and easy to use. The develop-
ment of web application for the post office is developed
using Microsoft Studio IDE that takes the advantage of
object-oriented database system Db4o. Further studies
can be done to explore new capabilities and potentials of
Db4o like data mining, clustering of object-oriented da-
tabase, etc.
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