with a set of services by invoking one or several of
the methods they support. The way messages are
exchanged between the business process and the
Service Methods is described through the concept of
Activity. Activities can then be combined into com-
plex algorithms through the BPEL concept of Struc-
tured Activities. The proposed model supports the
allocation of such services to Shared Workspace
Environments. Methods represent API calls, or func-
tionality, of such services.
3 ARCHITECTURE AND CORE
SERVICE DESCRIPTION
In order to support e-Processes a layered service
architecture that makes use of established work,
initiatives and standards in the web services domain
(including BPEL, WS-Security, WS-Coordination
and Transaction) has been specified. Each layer
represents the main building blocks enabling the
project workspace through the three identified roles,
namely Work Space Service Provider (WSSP),
Third-Party Service Providers (TPSP) and Work
Space clients (WSC).
Referring to Figure 2, boxes within the WSSP
services represent the essential core services neces-
sary for the setting-up, operation and coordination of
a project workspace. The service manager box pro-
vides access to the API functions necessary for all
aspects of invocation, registration and de-
registration of services from third-party service
providers, as well as their publication in the local
(WSSP maintained) UDDI registry. The Business
Process Specification Layer (BPSL) includes the
API functions that enable service composition in
order to implement a given business process. This is
based on the following core services concerned with
service coordination, transaction, and security:
• Security Service: This service builds and
implements the WS-Security specification.
WS-Security defines the core facilities for
protecting the integrity and confidentiality
of SOAP messages, and is specified in a
way that accommodates a wide range of se-
curity models (including identity-based se-
curity, access control lists, and capabilities-
based security) and encryption technolo-
gies.
• Coordination Service: This service builds
on WS-Coordination, which defines an ex-
tensible framework for coordinating activi-
ties using a coordinator and set of coordina-
tion protocols. This enables participants to
reach consistent agreement on the outcome
of distributed activities. The coordination
protocols that can be defined should ac-
commodate a wide variety of activities, in-
cluding protocols for simple short-lived op-
erations and protocols for complex long-
lived business activities. It provides consis-
tent control of the execution of the services
forming the composite service.
• Transaction Service: It is based on WS-
Transaction, which leverages WS-
Coordination by (a) extending the WS-
Coordination context to create a transaction
context, (b) augmenting the activation and
registration services with a number of addi-
tional services (Completion, Completion
WithAck, PhaseZero, 2PC, Outcome Noti-
fication, BusinessAgreement, and Busines-
sAgreementWithComplete), and (c) defin-
ing two particular coordination types:
Atomic Transactions (AT) and Business
Activity (BA).
Figure 2: Proposed Service-oriented Architecture.
The Third Party Service Provider Layer (TPSP)
represents all web-serviced applications that are
ready for invocation and use as part of a service
composition exercise in order to implement a busi-
ness process. As explained in section 2, any existing
EIS or legacy application has the potential to be
promoted to become a web service. The members of
a workspace (WSC) can use adapted software cli-
ents made available by the service provider (WSSP)
to collaborate and invoke services. They have also
the possibility to extend their existing portal (or EIS
Service Manager
API
RMI/SOAPRMI/SOAP
SOAPSOAP
RMI/SOAP RMI/SOAPSOAP SOAP
INTERNET
INTERNET
Service Discovery
Service Publication
Service Inspection
Security Communication
Coordination
Transaction
Business Process Specification Layer
Native APIs
Legacy
System 2
WSDL
SOAP SOAP
WSDL
Native APIs
Semantic
Representation
Service
Intelligent
Resource
Discovery
Service
Categorisation
Service
Multi-Modal
Interfaces
Web-Serviced
Enterprise
Information
Systems
Service
Infrastructure
Management/
Service
Composition
Semantic
Integration
Secure Service
Transactions
Coordination
Service Invocation
Semantic
Compatibility
Service
Ontology
Service
WSDL
Legacy
System 1
SOAP
Legacy
System 3
Workspace
Management
Service
INTERNET
WSDL
Legacy
System 1
SOAP
ONTOLOGY-BASED DYNAMIC SERVICE COMPOSITION USING SEMANTIC RELATEDNESS AND
CATEGORIZATION TECHNIQUES
115