Service Oriented Architecture

Abstract

Service Oriented Architecture (SOA) has been proposed as a way to model distributed software development that surpasses the traditional Distributed

Object Architecture (DOA) practices in many areas. However, no empirical studies have been conducted toverify the claimed benefits. This study is a first attempt at presenting empirical evidence regarding the benefits of SOA. It is a comparison between traditional DOA using the EJB technology and SOA using Web Services. These two technologies were compared on the

basis of code size (LOC) and development time. The

results show that, as a whole, the subject application

was faster to develop using the SOA method. However,

the LOC developed with the SOA method was almost

twice that developed with the EJB method.

Key Words: SOA, Web Services, EJB, SOA

experimentation

1. Introduction

The traditional Distributed Object Architecture

(DOA) used in building multi-tier Web based

applications can reach its limit when highly distributed

heterogeneous systems need to interoperate. Some

modern web applications are using a new computing

model where services are treated as self-contained

modules that can be advertised, discovered, composed,

and negotiated on demand.

Service Oriented Architecture (SOA) is a model for

designing, building, and deploying distributed software

applications. It emphasizes loosely coupled design

approaches where disparate systems, with different

computing platforms, can collaborate without major

changes to their existing core architectures.

Despite wide industry and academic attention, no

evidence has been presented to substantiate the claimed

benefits of SOA. IT managers are faced with anecdotal

evidence and strong commercial campaigns. Therefore,

empirical studies are needed to evaluate the value of

SOA.

This paper reports on a first attempt to attain

empirical evidence regarding the benefits of SOA. It is

a comparison between traditional DOA using the EJB

technology and SOA using Web Services. These two

technologies were compared on the basis of code size

and development time.

The main contributions of this paper are:

• An empirical investigation SOA

• A comparison of the EJB and Web Services

technologies

• A highlight of the value of tool support in

implementing both technologies

The paper is structured as follows: section 2

provides background on Web Services and EJB

technologies, section 3 describes the experiment in

details, section 4 presents the results, section 5

discusses the results, and section 6 concludes the paper.

2. Web Services and EBJ Essentials

Service oriented architectures use several

technologies, including EJBs and Web Services.

2.1 Enterprise Java Beans

Enterprise Java Beans (EJB) [6] is a Java

implementation of distributed component architectures.

This technology deals with server-side components that

adhere to standards in order to attain high degree of

reusability. EJBs run within middleware application

servers that provide enterprise-level services such as

load balancing, and transaction management.

An EJB is a component that encapsulates certain

business logic and can be deployed to distributed

environments. For example, an authentication EJB can

handle users’ access to a company’s enterprise services.

Client applications can use prewritten EJBs by using a

standard lookup and invocation mechanism.

2.2 Web Services

Web Services [3, 4] are self-contained specialized

applications that can be accessed by other systems over

the Internet. They are modular by design and can be

integrated into other applications on the Web. Services

can be published, located, and used over the Web.

A Web Services architecture is based on three

actors: service provider, service broker and service

requester [5]. Service requesters consult with service

brokers to find the most suitable services. Then, service

requesters bind to provided services. Web Services

exchange data in XML. The textual nature of XML

ensures platform independence for Web Services.

Web Services Description Language (WSDL)

defines