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document Web Services Notification (WS-Notification) has been
partitioned into three separate specifications in a Web Services Notification
Framework: WS-BaseNotification, WS-BrokeredNotification, and WS-Topics.
An announcement from Akamai, The Globus Alliance, HP, IBM, Sonic Software,
and TIBCO describes the release of three new specifications providing a scalable
publication/subscription messaging model and the ability to model stateful
resources using Web services. The new WS-Notification and WS-Resource Framework
are designed to integrate Grid and Web services standards, and represent "a
common, standards-based infrastructure will be available for business
applications, Grid resources and systems management."
Stateful resources are "elements that can be modeled including physical
entities (such as servers) to logical constructs (such as business agreements
and contracts). Access to these stateful resources enables customers to realize
business efficiencies including just in time procurement with multiple
suppliers, systems outage detection and recovery and Grid-based workload
balancing."
Web Services Notification as presented in WS-Notification "can
automatically trigger an action in the IT infrastructure once certain criteria
have been met. This can include suppliers automatically being notified to bid to
replenish inventory once current inventory drops to a set level. Several
suppliers can be notified of this depletion in inventory and WS-Notification can
be set up so that only the supplier with the best bid fills the order." The
WS-Resource Properties document "defines how data associated with a
stateful resource can be queried and changed using Web services technologies.
This allows clients to build applications to efficiently read and update data
associated with resources, such as contracts, servers or purchase orders." The
WS-Resource Lifetime document provides a means for the user to
"specify the period during which a resource definition is valid. For example, WS
Resource Lifetime can automatically update suppliers from all systems once
contracts or service level agreements expire, or deleting products from
inventory systems that are no longer being manufactured."
Bibliographic Information and Overview
Three of the six planned WS-Resource Framework Specifications have been
released as of 2004-01-20.
-
Web
Services Notification (WS-Notification). By Dave Chappell (Sonic
Software), Steve Graham (Editor, IBM), Amy Lewis (TIBCO Software), Nataraj
Nagaratnam (IBM), Peter Niblett, IBM (Editor, IBM), Jay Parikh (Akamai
Technologies), Sanjay Patil (SAP), Shivajee Samdarshi (TIBCO Software), Steve
Tuecke (Globus / Argonne National Laboratory), William Vambenepe
(Hewlett-Packard Development Company), Bill Weihl (Akamai Technologies). Version
1.0. 1/20/2004. Copyright (c) 2003, 2004 International Business Machines
Corporation, Sonic Software Corporation, SAP AG, Hewlett-Packard Development
Company, Akamai Technologies Inc., and Tibco Software Inc. 70 pages.
Abstract: "The Notification model, where a service provider, or other entity,
initiates messages based on a subscription or registration of interest from a
service requestor, is a common pattern that should be standardized in Web
services. This document specifies a standard Web services approach to
notification using a topic-based pub/sub pattern. It includes: standard message
exchanges to be implemented by service providers that wish to participate in
Notifications, standard message exchanges for a notification broker service
provider (allowing publication of messages from entities that are not themselves
service providers), operational requirements expected of service providers and
requestors that participate in notifications, and an XML model that describes
topics."
WS-Notification leverages the work defined in the WS-Resource family of
specifications. WS-Resource defines the relationship between a Web service and
stateful entities (known as WS-Resources, or just resources) by defining a
so-called implied resource pattern. WS-Resource standardizes the use of
WS-Addressing to specify how a Web service message must contain the identity of
a WS-Resource to be used as context for processing the message. Several aspects
of WSNotification, particularly Subscriptions, utilize this concept.
WS-Notification also uses WS-ResourceProperties. WSResourceProperties defines a
mechanism by which a WSDL portType can be associated with an XML element that
describes the data associated with a resource. This specification includes
standard message exchanges associated with reading and writing a resource's
data. WS-Notification uses WS-ResourceLifetime to provide direct, immediate
destruction of resources as well as scheduled destruction of resources, based on
a leasing or time-based model..." [adapted from the spec]
-
Web
Services Resource Properties (WS-ResourceProperties). By Steve Graham
(Editor, IBM), Karl Czajkowski (Globus / USC/ISI), Donald F. Ferguson (IBM), Ian
Foster (Globus / Argonne), Jeffrey Frey (IBM), Frank Leyman (IBM), Tom Maguire
(IBM), Nataraj Nagaratnam (IBM), Martin Nally (IBM), Tony Storey (IBM), Steve
Tuecke (Globus / Argonne), William Vambenepe (Hewlett-Packard), and Sanjiva
Weerawarana (IBM). Version 1.0. January 20, 2004. Copyright (c) 2004
International Business Machines Corporation and Hewlett-Packard Development
Company. 37 pages.
Abstract: "The relationship between Web services and stateful resources is
defined in [this specification]. This relationship is described as the
implied resource pattern. In the implied resource pattern, messages to a
Web service include a component that identifies a stateful resource that must be
use as context to execute the message. We refer to a stateful resource
associated with a Web service as a WS-Resource. This document standardizes the
means by which the definition of the properties of a WS-Resource may be declared
as part of a Web service interface. The declaration of the WS-Resource's
properties represents a projection of or a view on the WS-Resource's state. This
projection represents an implied resource type which serves to define a basis
for access to the resource properties through Web service interfaces..."
-
Web
Services Resource Lifetime (WS-ResourceLifetime). By Jeffrey Frey
(IBM), Karl Czajkowski (Globus / USC/ISI), Donald F. Ferguson (IBM), Ian Foster
(Globus / Argonne), Frank Leyman (IBM), Tom Maguire (IBM), Nataraj Nagaratnam
(IBM), Martin Nally (IBM), Tony Storey (IBM), Steve Tuecke (Globus / Argonne),
William Vambenepe (Hewlett-Packard), and Sanjiva Weerawarana (IBM). Version 1.0.
January 20, 2004. Copyright (c) 2004 International Business Machines Corporation
and Hewlett-Packard Development Company. 22 pages.
Abstract: "The definition of a resource and the relationship between Web
services and resources is defined in the document titled Modeling Stateful Resources with Web services. We refer to
a stateful resource in this context as a WS-Resource. This specification defines
message exchanges to standardize the means by which a WS-Resource may be
destroyed, and resource properties [WS-ResourceProperties] that may be used to
inspect and monitor the lifetime of a WS-Resource. This specification defines
two means of destroying a WS-Resource: immediate destruction and time-based,
scheduled destruction."
"The lifecycle of a WS-Resource is defined as the period between its
instantiation and its destruction. The WS-ResourceLifetime specification
standardizes the means by which a WS-Resource can be destroyed. The
specification also defines the means by which the lifetime of a WS-Resource can
be monitored. However, this specification does not prescribe (nor proscribe) the
means by which a WS-Resource is created... Normally, a service requestor's
interest in a WS-Resource is for some period of time, rarely is it indefinite.
In many scenarios, it is appropriate for clients of a WS-Resource to cause its
immediate destruction. The immediate destruction of a WS-Resource may be
accomplished using the message exchanges defined in this specification...
In addition, this specification defines the means by which a resource may be
destroyed after the expiration of a period of time. In a distributed computing
environment, a client may become disconnected from the service provider's
endpoint and therefore may be unable to, or unwilling to cause the immediate
destruction of the WS-Resource. This specification defines the means by which
any client of a WS-Resource may establish and extend the scheduled termination
time of a WS-Resource..." [from the spec
Introduction]
Royalty-Free Licensing Planned
A statement
from IBM relative to the WS-Resource Framework documents declares that "The
authors of the WS-Resource Framework documents intend to submit an updated
version of them to a standards body, in which case they intend to grant a
Royalty-Free license to their necessary patent claims."
A similar statement
from HP was made relative to WS-Notification: "The Authors of the Specification
intend to submit revised versions of the Specification to a standards body, in
which case they intend to grant a Royalty-Free (zero royalties with other
reasonable and non-discriminatory terms) license to their necessary patent
claims..."
WS-Resource Framework Specifications
The WS-Resource Framework is inspired by the work of the Global Grid Forum's
Open Grid Services
Infrastructure (OGSI) Working Group. Indeed, it can be viewed as a
straightforward refactoring of the concepts and interfaces developed in the OGSI
V1.0 specification in a manner that exploits recent developments in Web services
architecture..."
Summary from the WS-Resource Framework FAQ
document: "The WS-Resource Framework (WSRF) is a set of six Web services
specifications that define what is termed the WS-Resource approach to modeling
and managing state in a Web services context. To date [2004-01-20], drafts of
three of these specifications have been released, along with an architecture
document that motivates and describes the WS-Resource approach to modeling
stateful resources with Web services..."
- WS-ResourceLifetime: defines mechanisms for WS-Resource destruction,
including message exchanges that allow a requestor to destroy a resource, either
immediately or by using a time-based scheduled resource termination mechanism.
- WS-ResourceProperties: defines how the type definition of a
WS-Resource can be associated with the interface description of a Web service,
and message exchanges for retrieving, changing, and deleting WS-Resource
properties.
- WS-Notification: defines mechanisms for event subscription and
notification using a topic-based publish/subscribe pattern.
- WS-RenewableReferences: defines a conventional decoration of a
WS-Addressing endpoint reference with policy information needed to retrieve an
updated version of an endpoint reference when it becomes invalid.
- WS-ServiceGroup: defines an interface to heterogeneous by-reference
collections of Web services.
- WS-BaseFaults: defines a base fault XML type for use when returning
faults in a Web services message exchange.
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