Information Technology Reference
In-Depth Information
Policy does not support capabilities of negotiation,
monitoring agreement compliance at runtime
which SLA management needs. But WS-Policy is
an extensible language and as one of W3C SOA
standard stack, it has potential to be used for SLA
representation.
pabilities and requirements of service providers
and customers. The support of defining metrics
and measurement is limited. A domain-specific
model or domain ontology needs to be defined
when using WSDM in SLA. WSDM provides
an event model which could be used for SLA
monitoring, but it does not provide support for
SLA negotiation.
WS-Agreement
Web Service Management
(WS-Management)
WS-Agreements proposed by OGF (http://www.
ogf.org/) is a popular standard to be aggregated
into Web service architecture to support the man-
agement of non-functional requirements in Web
service (Garcia et al., 2006). It is a protocol for
establishing an agreement on the usage of services
between a service provider and a consumer (http://
www.ogf.org/documents/GFD.107.pdf).
WS-Agreement has more expressive power
to describe service level objectives, which state
the requirements and capabilities of each party on
the availability of resources and service qualities.
It has been widely used in Grid communities.
Seidel et al. (Seidel et al. 2007) identified many
research projects which employ WS-Agreement
for SLA representation for resource management
and scheduling.
Web Service for Management (WS-Management)
(http://www.dmtf.org/standards/wsman), another
SOA management protocol, is a specification for
managing devices, computers, Web services and
applications using Web service. It was proposed
by Distributed Management Task Force (DMTF)
(http://www.dmtf.org/home) and published in
2004 with support from IT companies such as
AMD, Dell, Intel, Microsoft and Sun. DMTF
is a standards organization that develops and
maintains standards for systems management of
IT environments in enterprises and the Internet.
WS-Management has some overlapping area
with MUWS of WSDM but has addition on access-
ing resources. WS-Management can be regarded
as sort of implementation of management model
namely “Common Information Model” proposed
by DMTF. Similar to WSDM, WS-Management
aims at management of services, devices and ap-
plications, hence has same disadvantage as WSDM
does. WS-management is not strong enough to be
used in SLA. For example, it does not provide a
negotiation model for SLA, not appropriate for
defining agreement between customer and service
provider.
Web Service Distributed Management
The Web Services Distributed Management
(WSDM) (http://www.oasis-open.org/commit-
tees/tc_home.php?wg_abbrev=wsdm) standard
published by OASIS (http://www.oasis-open.org/
home/index.php) defines the methods, structure,
and specification of a system for managing net-
work resources (e.g. printers, routers, servers and
services) and for managing Web service. WSDM
contains two parts: (i) Management Using Web
services (MUWS) and (ii) Management of Web
services (MOWS) (http://www.oasis-open.org/
committees/tc_home.php?wg_abbrev=wsdm).
However, as the aim of WSDM is about man-
agement using Web service and management of
Web service, rather than focus on defining ca-
Survey Findings
Research findings from the survey are summarised
as follows:
1. The survey shows that WS-Agreement and
WS-Policy can be two candidate standards to be
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