ServiceGlobe: Distributing E-Services
Across the Internet
Markus Keidl Stefan Seltzsam Konrad Stocker
Universit£t Passau
Fakult£t fiir Mathematik und Informatik
94030 Passau, Germany
(last name)©db,
fmi. uni-passau, de
Alfons Kemper
1 Introduction
The next generation of Internet applications is emerg-
ing:
e-services.
By an e-service, we understand an au-
tonomous software component that is uniquely identi-
fied by an URI and that can be accessed by using stan-
dard Internet protocols like XML, SOAP, or HTTP.
An e-service may combine several applications that a
user needs, such as the different pieces of a supply-
chain architecture. For the end-user, however, the en-
tire infrastructure will appear as a single application.
The ServiceGlobe system provides a platform on
which e-services (also called
services
or
Web services)
can be implemented, stored, published, discovered, de-
ployed, and dynamically invoked at arbitrary Inter-
net servers participating in the ServiceGlobe feder-
ation. While current approaches mainly try to in-
tegrate existing services which are already running
on dedicated servers, we provide the functionality
to specify new, composite services which can be de-
ployed dynamically on arbitrary ServiceGlobe enabled
servers/devices. Besides the support of standard func-
tionality of a service platform like SOAP/XML com-
munication, a transaction system, or a security system,
the ServiceGlobe platform addresses also various opti-
mization issues like load balancing or network oriented
deployment during service execution.
Due to its potential of changing the Internet to
a platform of application collaboration and integra-
tion, e-service technology gains more and more atten-
tion in research and industry; initiatives like HP Web
Services Platform [WSP], Sun ONE [Sun], or Mi-
crosoft .NET [NET] show this development. Although
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Proceedings of the
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all of these frameworks share the opinion that services
are important for easy application collaboration and
integration, they handle the subject from a
different
point of view. Their approaches are server-centric and
their focus is on providing a complete infrastructure to
implement these services. Our approach is network-
centric, focusing on the distributed execution of ser-
vices and an elaborate selection and distribution of
the services they deploy.
2 Architecture of ServiceGlobe
The ServiceGlobe system provides a lightweight infra-
structure for a distributed, extensible e-service plat-
form. It is completely implemented in Java Release 2.
In this section, we present the basic components of this
infrastructure. Basically we distinguish two different
types of services: external and internal e-services.
External services
are existing, stationary services,
currently deployed on the Internet, which are not pro-
vided by ServiceGlobe itself. Such services may be
realized on arbitrary systems on the Internet having
arbitrary interfaces for their invocation. Since we want
to be able to integrate these services independent of
their actual invocation interface, e.g., SOAP or RPC,
we use
adaptors
to transpose internal requests to the
external interface and vice versa. This way, we are
also able to access arbitrary applications, e.g., ERP
applications. Thus external services can be used like
internal services and, from now on, we consider only
internal services.
Internal services
are native ServiceGlobe e-services.
They are implemented in Java using the e-service API
provided by the ServiceGlobe system. ServiceGlobe
services use SOAP to communicate with other ser-
vices. Services receive a single XML document as in-
put and generate a single XML document as output.
There are two kinds of internal services, namely
dy-
namic
e-services and
static
e-services. Static services
are
location_dependent,
i.e., they cannot be executed
dynamically on arbitrary ServiceGlobe servers. Such
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