Asynchronous Mobile Web Services: Concept and Architecture
Fahad Aijaz, Bilal Hameed, Bernhard Walke
RWTH Aachen University, Faculty 6
Communication Networks
Kopernikusstr. 16, 52074 Aachen
{fah, bhd}@comnets.rwth-aachen.de
Abstract
Today, mobile devices are capable of providing services
instead of just being service consumers. These services de-
ployed on mobile devices are known as Mobile Web Services
(Mob-WS). In this paper, a middleware for long running
Mob-WS that avoids the overheads of long durational syn-
chronous Mob-WS in introduced. A concept and archi-
tecture of such asynchronous Mob-WS middleware is pre-
sented. Moreover, the middleware subsystem, the high-
level architecture and control flow are presented in detail.
Since every service has application specific requirements,
the service data representations that eases the s ervice de-
ployment process are described. In order to verify the no-
tion, a prototype with a focus on Wireless Sensor Networks
(WSN) has been developed and briefly discussed. Finally,
the manuscript is concluded and future research directions
are identified.
1 Introduction
The term “Mob-WS” cannot be given any standard defi-
nition, since it depends on the domain and context it is used
in. However, in order to provide and publish Mob-WS, just
like traditional Web Services, it is important to ensure their
conformance to the Web Services standards and integration
with the standard underlying communication infrastructure
and protocols. Since the traditional Web Services are self
contained software components that are identified by a Uni-
form Resource Identifier (URI) [2], therefore Mob-WS shall
be developed and deployed in a way that coincides with the
official definition of Web Services. Within the scope of this
work, Mob-WS are defined as Web Services that are de-
ployed on mobile devices and are published over the Inter-
net, wireless network or within the operators’ network.
In this paper, a concept and architecture of a middleware
for asynchronous Mob-WS is introduced to perform long-
lived operations. The work is based on the existing Mob-
WS framework first presented in [6]. Since synchronous
Mob-WS are not a feasible choice for long durational tasks,
therefore a need for asynchronously accessible Mob-WS
arises. In section 2, black-box architecture of the middle-
ware is presented and the generic control flow is explained.
Section 3 elaborates the deployment process and discusses
the data representation requirements. Furthermore in sec-
tion 4 a proof-of-concept prototype for WSN optimization
is briefly presented. Performance measurement results are
explained in section 5 followed by conclusion and future
directions in section 6.
2 Asynchronous Services’ Middleware
The asynchronous Mob-WS middleware provides a
foundation to develop and deploy asynchronous long-lived
services, not asynchronous messaging. This is because
asynchronous messaging does not necessarily implies that
the deployed services are asynchronous in nature. Since
asynchronous services start and continue to perform their
tasks over a longer duration of time, therefore, the need to
be able to monitor and control such services becomes es-
sential. In this section, the high-level architecture is pre-
sented since the focus is solely on the concept and architec-
ture. The implementation and further technical details are
planned to be published in a separate paper.
The concept of Mob-WS involves two basic roles,
termed as Web Service Consumer (WS-C) and Web Ser-
vice Provider (WS-P). Within the context of this work, we
will focus on Peer-to-Peer (P2P) interaction, where both the
WS-C and WS-P are mobile nodes.
2.1 High-Level Architecture and Control
Flow
In order to build a system of asynchronous Mob-WS
three different types of endpoints are defined to cater three
distinct roles. These are the Instance, Factory, and Observer
components which form a subsystem within the middleware