Introduction

General reference document on statefulness in web services. [Draft document in preparation. Provisional and incomplete]

Contents

• Initiatives and Projects
  • Open Grid Services Infrastructure Working Group (OGSI WG)
  • Web Services Resource Framework
  • Web Services Notification Framework
  • North-East Regional e-Science Centre (NERESC)
  • W3C Web Services Description Working Group
  • Business Process Execution Language (BPEL)
  • OASIS Web Services Resource Framework Technical Committee
  • OASIS Web Services Notification Technical Committee
  • OASIS Web Services Composite Application Framework TC
  • WS-Events
  • WS-Eventing
• General: Articles, Papers, Presentations, Reports, News

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Initiatives and Projects

References to key specifications (being) produced within several working groups, technical committees, and industry initiatives. [Incomplete, intended to be representative].

General: Articles, Papers, Presentations, Reports, News

• [March 07, 2005] "Exploring WS-Notification: Building a Scalable Domotic Infrastructure." By Marco Aiello (Assistant Professor and Head of the Distributed Systems and Service-Oriented Computing Research Program, DIT, University of Trento, Italy), Manuel Zanoni, and Alessandro Zolet. In Dr. Dobb's Journal (April 2005), pages 48-51. "Home appliances are evolving at a pace well beyond the capabilities designers of X10 -- a standard that uses powerlines to remotely control home devices -- ever expected. Equipping home devices with processors and wireless connectivity has become affordable and painless, thanks in part to wireless connectivity Standards such as GSM, GPRS, Wi-Fi (IEEE 802.11), Bluetooth (IEEE 802.15.1), and ZigBee (IEEE 802.15.4). Still, one of the challenges users face is having devices that make proper use of this communication infrastructure. What are appropriate messaging schemes for these loosely coupled autonomous devices? How can these devices discover each other and interact? Interestingly, XML-based web services offer an answer to this question. In this article, we will examine WS-Notification, a web-service publish/subscribe protocol that we apply to a "domotic" living environment for elderly adults. In particular, we use WS-Notification to integrate different sensors and actuators in a home environment, with the goal of detecting life-threatening situations, such as when elderly inhabitants of the home fall... With WS-Notification, you have standard ways for creating an ontology of topics for describing events, a communication mechanism between event producers and consumers, and a policy for subscriptions and event forwarding. In short, WS-Notification lets you build platform-independent scalable systems made of autonomous nodes asynchronously exchanging messages — exactly what you need in the context of domotics... We have deployed the WS-Notification server in a home with the goal of monitoring elderly citizens and detecting if they fall. Indeed, one of the most common accidents in the aging population is the accidental fall that, especially if undetected, may have dangerous effects. In Great Britain, accidental falls constitute about 30 percent of the home accidents of people over 65. A number of sensors can be used to detect this hazardous situation; for instance, one can place an array of infrared sensors at the floor level, one can equip the person with an accelerometer, or one can use fixed cameras. With the notification server, we can actually combine more sensors to reduce the amount of false positives. In particular, we use a custom-made accelerometer built by ITC-irst and standard fixed video cameras. State-of-the-art posture-recognition software built by CNR-IMAG lecce analyzes the images and classifies postures into three main categories: standing, sitting, and laying. The rule engine fuses the data from the accelerometer and image-analysis software, and identifies potentially dangerous situations. The information of each sensor taken alone is not enough to detect a fall with an acceptable reliability. Home networking in general and domotics in particular are applications where WS-Notification can be successfully applied. While not all home appliances will implement a web-service stack that goes from SOAP messages up to WSDL or even BPEL descriptions, many will aggregate home functional units and offer interfaces for the external world (and vice versa). Home sensor networks will have different forms of computationally less-expensive communication and will use web-service-ready devices as gateways for higher level communication..." See similarly online "Opening the Home: A Web Service Approach to Domotics" (entry following).

• [March 07, 2005] "Opening the Home: A Web Service Approach to Domotics." By Marco Aiello and Maurizio Marchese (DIT - Univ. of Trento); Paolo Busetta and Gaetano Calabrese (ITC-irst). Technical Report #DIT-04-109, University of Trento, Department of Information and Communication Technology, December 2004. 14 pages. "The pervasiveness of smart appliances in the home, the increase of computational power of traditional home appliances, and the widespread adoption of wireless networking are creating a unique opportunity in domotics. The challenge lies in moving from a set of isolated devices towards a network of home appliances interoperating and scaling seamlessly to provide services to the home user. The major barriers to achieve this is the abundance of non-interoperable domotics standards and the lack of a generally agreed architecture. We propose a service-oriented architecture (SOA) for the interaction of home appliances and the creation of value added services based on standard web services. In particular, we propose the use of WS-Notification as the basic layer for device interoperation. We have experimented the proposed architecture in the context of a project for the assistance of the elder citizen. We provide preliminary results for the case of fall-detection. Addressing the operability of different sensors yields, for the first time, to an integrated and scalable system that detects falls by fusing data transported via a truly vendor-independent publish/subscribe mechanism... The novelty of the approach lies in the openness of the resulting home network where any device is seamlessly added and removed independently of its hardware, operating system and network interface. The approach is based on WS-Notification. To the best of our knowledge, this is the first implementation of the standard in a prototype deployed for a concrete application. The WS-Notification server has been implemented and tests are underway in a real home environment where two type of sensors have been deployed: a wearable custom accelerometer and a videocamera. Furthermore, registration of events and modification of the event tree is performed by a PDA. The test case is the fall detection of the elderly at home. Previous approaches to fall detection have used one sensor only. The open architecture we propose allows the use of distinct sensors for fall detection..."

• [May 01, 2004] "Stateful Interactions in Web Services: A Comparison of WS-Context and WS-Resource Framework." By Mark Little (Arjuna Technologies Limited), Jim Webber (University of Newcastle upon Tyne), and Savas Parastatidis (North-East Regional e-Science Center - NEReSC, Newcastle, UK). In Web Services Journal Volume 4, Issue 5 (May 2004). "In July 2003 a consortium of Web services vendors released the Web services Composite Application Framework (WS-CAF) to the community. WS-CAF is comprised of three specifications that together provide a means of reliably composing individual Web services into larger aggregate applications. The cornerstone of this suite is the management of stateful interactions between Web services that is the domain of the WS-Context specification. WS-CAF was subsequently submitted to OASIS and an effort to standardize the framework is currently underway. In January 2004 a group of industry and academic practitioners from the Grid community released [the first parts of] the Web Services Resource Framework specifications. WS-RF will support stateful interactions between consumers and resources hosted by Web services. Clearly there is some overlap between the WS-Context and WS-RF approaches since both support stateful interactions on top of the stateless interaction model championed by Web Services Architecture (WSA). This article examines the different approaches taken by WS-Context and WS-RF, concentrating in particular on how each approach facilitates stateful interactions in composite Web services-based applications... While both WS-Context and WS-RF can be used to enable stateful interactions between Web services and their consumers, the models they adopt to achieve this are very different, and as a consequence the scenarios in which they are best deployed are also different. The WS-RF approach is based on an addressing scheme for back-end resources hosted by Web services. This addressing information can be used as a means of correlating and routing message exchanges with those back-end resources and thus as a means of achieving stateful communication. WS-Context assumes that the back-end implementation details of a service are private. It is deliberately noninvasive and deals only with context management and propagation of contexts to services. What precisely is done to map a particular application level message plus context onto specific back-end resources is safely out of scope. For single consumer-server interactions the WS-RF approach is certainly lightweight. However for interactions involving multiple services, the WS-Context approach scales readily to support distributed activities. Thus WS-RF might be suitable as a point-to-point solution for integrating two systems, but in the general case with systems composed from many Web services, WS-Context is the natural choice..."

• [March 05, 2004] From Open Grid Services Infrastructure to WS-Resource Framework: Refactoring and Evolution. Version 1.1. March 05, 2004. 20 pages. By Karl Czajkowski (Globus Alliance / USC Information Sciences Institute), Don Ferguson (IBM), Ian Foster (Globus Alliance / Argonne National Laboratory), Jeff Frey (IBM), Steve Graham (IBM), Tom Maguire (IBM), David Snelling (Fujitsu Laboratories of Europe), and Steve Tuecke (Globus Alliance / Argonne National Laboratory). With contributions and feedback from Sonny Fulkerson, Carl Kesselman, Susan Malaika, Martin Nally, Jeff Nick, Chris Sharp, Tony Storey, and Jay Unger, also from Malcolm Atkinson and Savas Parastatidis. "The Open Grid Services Infrastructure specification version 1.0 (OGSI), released in July 2003, defines a set of conventions and extensions on the use of Web Service Definition Language and XML Schema to enable stateful Web services. It introduces the idea of a stateful Web services and defines approaches for creating, naming, and managing the lifetime of instances of services; for declaring and inspecting service state data; for asynchronous notification of service state change; for representing and managing collections of service instances; and for common handling of service invocation faults. In January 2004, the WS-Resource Framework was proposed as a refactoring and evolution of OGSI aimed at exploiting new Web services standards, specifically WS-Addressing, and at evolving OGSI based on early implementation and application experiences. The WS-Resource Framework retains essentially all of the functional capabilities present in OGSI, while changing some of the syntax (e.g., to exploit WS-Addressing) and also adopting a different terminology in its presentation. In addition, the WS-Resource Framework partitions OGSI functionality into five distinct, composable specifications. In this document, we explain the relationship between OGSI and the WS-Resource Framework and the related WS-Notification family of specifications, explain the common requirements that both address, and compare and contrast the approaches taken to the realization of those requirements." See also the overview page from IBM. [source PDF]

• [March 05, 2004] The WS-Resource Framework. By Karl Czajkowski (Globus Alliance / USC Information Sciences Institute), Donald F Ferguson (IBM), Ian Foster (Globus Alliance / Argonne National Laboratory), Jeffrey Frey (IBM), Steve Graham (IBM), Igor Sedukhin (Computer Associates International), David Snelling (Fujitsu Laboratories of Europe), Steve Tuecke (Globus Alliance / Argonne National Laboratory), and William Vambenepe (Hewlett-Packard). Version 1.0. March 05, 2004. 18 pages. "The WS-Resource construct has been proposed as a means of expressing the relationship between stateful resources and Web services. We introduce here the WS-Resource framework, a set of proposed Web services specifications that define a rendering of the WS-Resource approach in terms of specific message exchanges and related XML definitions. These specifications allow the programmer to declare and implement the association between a Web service and one or more stateful resources. They describe the means by which a view of the state of the resource is defined and associated with a Web services description, forming the overall type definition of a WS-Resource. They also describe how the state of a WS-Resource is made accessible through a Web service interface, and define related mechanisms concerned with WS-Resource grouping and addressing. This paper provides an architectural overview of the WS-Resource framework. It motivates, introduces, and summarizes the interrelationships among five separate specification documents that provide the normative definition of the framework: WS-ResourceProperties, WSResourceLifetime, WS-RenewableReferences, WS-ServiceGroup, and WS-BaseFaults. We also describe how the WS-Resource framework can support the WS-Notification family of specifications for asynchronous notification." [source PDF]

• [March 05, 2004] "Web Services Notification Framework for Publish-Subscribe Notification Events." The technology previously outlined in a Web Services Notification (WS-Notification) specification has been elaborated in terms of a Web Services Notification Framework which supports Publish-Subscribe Notification for Web services. This framework has been developed by Akamai Technologies, Computer Associates International, Fujitsu Laboratories of Europe, Globus, Hewlett-Packard, IBM, SAP AG, Sonic Software, and TIBCO Software. The Web Services Notification Framework complements [and is part of] the Web Services Resource Framework, which includes the WS-ResourceProperties and WS-ResourceLifetime specifications and defines a family of specifications for accessing stateful resources using Web services. The Web Services Notification Framework currently includes three normative specifications. Web Services Base Notification (WS-Base Notification) describes "standard message exchanges to be implemented by service providers that wish to act in these roles, along with operational requirements expected of them." Web Services Brokered Notification (WS-BrokeredNotification) "defines the Web services interface for the NotificationBroker, which is an intermediary that allows publication of messages from entities that are not themselves service providers." Web Services Topics (WS-Topics) "defines a mechanism to organize and categorize items of interest for subscription known as 'topics' that are used in conjunction with the notification mechanisms defined in WS-Base Notification. It defines three topic expression dialects and specifies an XML model for describing metadata associated with topics." These specifications "implement the Notification pattern in which a service provider, or other entity, initiates messages based on a subscription or registration of interest from a service requestor. The Web Services Notification Framework defines how the publish/subscribe (pub/sub) pattern commonly used in Message-Oriented middleware products can be realized using Web services. This includes brokered as well as direct pub/sub which allows the publisher/subscribers to be decoupled and provides greater scalability..."

• [March 05, 2004] Modeling Stateful Resources with Web Services. Version 1.1. 03/05/2004. By Ian Foster (Globus Alliance / Argonne National Laboratory, Editor), Jeffrey Frey (IBM, Editor), Steve Graham (IBM, Editor), Steve Tuecke (Globus Alliance / Argonne National Laboratory, Editor), Karl Czajkowski (Globus Alliance / USC ISI), Don Ferguson (IBM), Frank Leymann (IBM), Martin Nally (IBM), Igor Sedukhin (Computer Associates International), David Snelling (Fujitsu Laboratories of Europe), Tony Storey (IBM), William Vambenepe (Hewlett-Packard), and Sanjiva Weerawarana (IBM). Copyright (c) 2003, 2004 Computer Associates International, Inc., Fujitsu Limited, Hewlett-Packard Development Company, International Business Machines Corporation and The University of Chicago. 24 pages. "The Web services architecture has been broadly accepted as a means of structuring interactions among distributed software services. Further standardization is now required to facilitate additional interoperability among services. One important area in which further standardization is required concerns interactions with stateful resources. In this paper, we address the constructs used to enable Web services to access state in a consistent and interoperable manner. We introduce the WS-Resource approach to declaring and implementing the association between a Web service and one or more named typed state components. In this approach, we model state as stateful resources and codify the relationship between Web services and stateful resources in terms of the implied resource pattern, a set of conventions on Web services technologies, in particular WS-Addressing. We describe a WS-Resource in terms of a stateful resource and its associated Web service. We also describe an approach for making the properties of a WS-Resource accessible through its Web service interface, and for managing a WS-Resource's lifetime."

• [February 26, 2004] "Grid Forum Backs Utility Computing Standards." By Paul Shread. From GridComputingPlanet.com (February 25, 2004). "The Distributed Management Task Force's effort to draft standards for utility computing has received the backing of the Global Grid Forum (GGF), the Grid computing standards-setting body. 'This is an important activity and we are excited to see the DMTF bring this group together, while simultaneously tapping related efforts, such as GGF's Open Grid Services Architecture (OGSA) and several new GGF research groups focused on commercial enterprise Grid application use cases and requirements,' Charlie Catlett, senior fellow at Argonne National Laboratory and chair of GGF, said in a statement... 'We have been working very closely with both DMTF for the past year, and in the past six months, also with OASIS, because these things are converging,' Catlett said. 'The efforts are indeed complementary, and where we have found intersection of activities we have created high-bandwidth liaison activities. For instance, we have a Common Management Model working group within GGF that was created by some folks who also participate in DMTF, and one of the objectives is cross-fertilization between Grid/utility computing and the distributed systems management world.' Catlett said 'the best sign of convergence' is the WS-Resource Framework (WSRF) effort to recast several key components of GGF's Open Grid Services Infrastructure (OGSI) specification into a set of Web services specs. The work is a joint effort between Grid services proponents from the GGF community and Web services proponents, Catlett said. 'The path forward for this is that WSRF specifications are most likely to be standardized via OASIS, where most Web services work is happening these days,' Catlett said. The GGF OGSI working group will serve a liaison function, and Catlett said he expects the WSRF-related OASIS technical committees to hold meetings at the thrice-yearly Grid forums. 'These are only a few of the ways we are discussing to work together with OASIS and DMTF,' Catlett said. Catlett also said he is 'personally very intrigued by DCML,' the Data Center Markup Language effort, and is 'trying to figure out how it might fit into Grid projects that I am doing without my GGF hat on. I definitely think DCML is quite interesting, but I have not followed what they're doing. We had extended an offer to them to do the work within GGF, but we haven't followed up. Regardless of where the work is done, I am hoping that we can form a liaison activity with them to make sure there is good exchange of ideas with the Grid community'..." See the announcement "DMTF Announces New Working Group for Utility Computing. OASIS, GGF and Industry Leaders Join Forces with DMTF to Further Management Standards for Utility Computing."

• [February 20, 2004] "Ian Foster on Recent Changes in the Grid Community." By Mark Baker (School of Computer Science, University of Portsmouth, UK) and Dejan Milojicic. In IEEE Distributed Systems Online Volume 5, Number 2 (February 2004). ['Mark Baker contacted Ian Foster (Senior Scientist, Distributed Systems Lab, Argonne National Laboratory; Arthur Holly Compton Professor of Computer Science, University of Chicago) just after the announcement of WSRF to discuss the recent changes and to get an idea of how these will affect the Grid community.'] Foster: "... The WSRF proposal is a refactoring of OGSI concepts to align better with Web services. The need for this refactoring became apparent when Web services vendors indicated that while they recognized the importance of OGSI concepts, they would not adopt OGSI as it was then defined. This response threatened to prevent the ubiquitous support for Grid infrastructure that was a primary motivator for OGSI. So, while we in the Globus Alliance had little enthusiasm for revisiting the OGSI design (we'd much rather be developing higher-level services than fiddling with infrastructure), we concluded that some refactoring was justified if it could affect the convergence of Grid and Web services. We teamed up with Web services architects to study this issue, and the result is WSRF. The changes from OGSI to WSRF are primarily syntactic but also represent some useful progress. The separation of OGSI functionality into six independent specifications simplifies adoption, the use of WS-Addressing is a step forward, and less aggressive use of XML Schema and WSDL 2.0 features will facilitate the use of available tooling. Do these benefits justify the disruption associated with a revision to the Grid infrastructure specification? At a purely technical level, it's debatable, but the fact that we now have strong support in the Web services community for Grid infrastructure is a huge achievement: it means we'll see WSRF support in core Web services products, which is wonderful news for the Grid community. Also, we shouldn't overemphasize the magnitude of the change: while there's certainly some work involved in converting from OGSI to WSRF, it doesn't appear to be substantial, and we're working to ease this transition. ... A beautiful feature of OGSI/WSRF is its deep integration of information service mechanisms. Any Grid service (or WS-Resource in WSRF) can declare service data (resource properties) that can be discovered, pulled, or pushed using standard mechanisms. The WS-Notification specification introduced with WSRF moves us another important step toward robust, feature-rich information services, by establishing interfaces that allow the exploitation of widely used message-oriented middleware. Thus, for example, a programmer who develops a file transfer service need only define some appropriate service data (resource properties) for that service to become immediately discoverable and be monitored. Given this underpinning, it becomes possible to define a wide range of information service components for discovery, monitoring, archiving, fault detection, and so forth..."

• [February 02, 2004] "New Specs Enrich Identity Federation." By James Kobielus. In Network World (February 02, 2004). "Last month, two industry groups released rival specifications that address the [event-notification services] requirement. One group — BEA Systems, Microsoft and Tibco Software — published a co-authored specification called Web Services Eventing (WS-Eventing); another, led by IBM, released its Web Services Notification (WS-Notification) spec. One important feature of WS-Eventing and WS-Notification is that they do not restrict the types or contents of messages that might serve as event notifications, nor do they restrict which entities might publish and subscribe to these messages. This means developers can begin to implement a general-purpose events infrastructure and, as Web services based on Simple Object Application Protocol become ubiquitous, make this infrastructure available to all applications and services. Notifications of user-generated events should be distributed in the same general-purpose infrastructure that handles system-level notifications. Inevitably, WS-Eventing and/or WS-Notification (or some converged specification that supersedes both) will be implemented in identity management systems to notify applications of important events concerning particular users. For example, an identity management environment might notify authorized applications that a user has connected to the network, logged on to a particular domain, moved to particular geographic coordinates and been granted particular roles, permissions and personalization settings... Liberty should reference WS-Eventing and/or WS-Notification in its identity management protocols, and the developers of WS-Federation should do likewise in future revisions. And as OASIS' Security Services Technical Committee continues development on SAML 2.0, it should begin to consider the need for a general-purpose event pub/sub environment for federated identity management. However, the SAML 2.0 feature list has more or less been finalized, and event notification isn't on it. Identity event notification will become a candidate for the eventual SAML 3.0 as soon as the federated identity management industry catches the vision and begins to compose standards with WS-Eventing and/or WS-Notification in mind..."

• [January 26, 2004] "Web Services Event Standards Take Big Step Forward." By Roy W. Schulte and Massimo Pezzini (Gartner). Gartner Research Note. Note Number: FT-22-0670. "On 20 January 2004, Akamai, The Globus Alliance, Hewlett-Packard, IBM, Sonic Software and TIBCO Software proposed two new Web services specifications. The first, WS-Notification, seeks to provide a standards-based means of publish-and-subscribe message delivery. The second, WS-Resource Framework, is actually a set of three standards that collectively describe a way to describe, access and then clean up after expired resources, such as a contract. WS-Resource Framework is intended to make grid resources accessible as Web services and to enable better manageability of the resources. On 7-January-2004, BEA Systems, Microsoft and TIBCO also published a specification for a Web services publish-and-subscribe standard, known as WS-Eventing... Publish-and-subscribe communication has been an important omission in Web services standards. But now, vendors are moving faster than expected to standardize the basic publish-and-subscribe design pattern in a Web services manner, based on Simple Object Access Protocol (SOAP). Based on the newly proposed WS-Eventing and WS-Notification specs, publish-and-subscribe standards could be ratified as early as mid-2005 — although major challenges still exist..."

• [January 23, 2004] "Grid and Web Services to Converge." By Peter Abrahams (Bloor Research). In IT-Analysis (January 23, 2004). "The two big computing ideas of the twenty first century grid computing and web services were brought closer together by an announcement this week at GlobusWorld the grid conference run by Globus Alliance. The Globus Alliance is a research and development project focused on enabling the application of Grid concepts to scientific and engineering computing and has developed the toolkit used by most scientific and university grid computing projects. It is an alliance between several university and laboratories in the US and Europe including Edinburgh. Web services have concentrated on creating an environment for 'applications on-demand' whereas grid has concentrated on providing 'computer-resources on-demand'. The announcement is made up of two new web services specifications that are necessary to make the grid computer resources available to the applications without the applications having to be grid aware. The two are the WS-Resource Framework and the WS-Notification specifications... WS-Resource Framework specification was contributed to by IBM, Globus and HP. It defines how to access a WS Resource through a web service. A web service is stateless whereas a WS-Resource is stateful, the state could be such things as data in a purchase order, current usage agreement for resources on a grid, or metrics associated with work load on a Web server. The framework describes a standard way to access a WS-resource by referencing it through an endpoint reference made up of the web services address and a resource id. It also defines how a web service can access or create new WS resources. The WS-Notification specification was contributed to by IBM, Globus, Akamai, HP, SAP, Tibco and Sonic. It provides a publish-subscribe messaging capability for Web Services. It enables changes or events to be published in a standard way and then notification send directly or via a broker. This is bringing some of Sonic's Enterprise Service Bus (ESB) concepts into a standards specification. WS-Notification is important for grid computing because it provides a standard way for grid resources such as web servers to notify grid schedulers of changes in state. Changes in state include coming on and off stream, being fully loaded or having spare capacity, having a fault that needs attention etc. All of this information is required for a grid scheduler to make informed decision on what resources to use next..."

• [January 22, 2004] "Globus Details Roadmap for Toolkit. Grid Computing Software to Gain Performance, Reliability and Usability." By Joris Evers. In InfoWorld (January 22, 2004). "The Globus Alliance in March [2004] plans to release an updated version of its Globus Toolkit for grid computing, adding performance, reliability and usability improvements and bug fixes since the 3.0 release last year, the group's co-leader said Wednesday. After the March release of version 3.2 the Globus Alliance plans to release version 4.0 in the third quarter, said Ian Foster, speaking at the GlobusWorld 2004 conference in San Francisco. A beta for the 3.2 release is set to start soon, he said. The 4.0 release of the Globus Toolkit will include draft WS-Resource Framework (WSRF) specifications, announced earlier this week at the GlobusWorld event. WSRF encompasses the WS-Resource Lifetime and WS-Resource Properties specifications introduced at the GlobusWorld event and intended to converge Web services and grid computing. WS-Resource Lifetime allows a user to specify a period during which a resource definition is valid and WS-Resource Properties defines how data associated with a stateful resource can be queried and changed using Web services technologies, according to a statement released Tuesday at GlobusWorld. 'We don't believe it is appropriate to wait for the specifications to wind their way through the standardization process to start implementing them,' Foster said. However, this does mean that the toolkit software will need revision when the final standards arrive, probably some time next year, but the toolkit will always offer backwards compatibility, he said. 'We are very concerned with supporting our existing user base and improving our software,' Foster said. The open source Globus Toolkit is a bundle of software to enable grid computing. It includes software services and libraries for resource monitoring, discovery and management, plus security and file management. The toolkit is a central part of science and engineering grid projects and used by IT vendors for commercial grid products..." See the following entry and Globus Toolkit web site.

• [January 21, 2004] "WS-Notification Spec Released." By Dave Chappell (Vice President, Sonic Software). From O'Reilly Developer Weblogs (January 21, 2004). "We jointly announced the WS-Notification spec yesterday. The co-authors include IBM, Akamai, HP, SAP, Sonic Software, The Globus Alliance, and TIBCO... I would best describe WS-Notification as 'Pub-sub for the Internet'. Its a Distributed broker-based pub-sub using web service interfaces. It doesn't directly address QoS issues such as exactly-once delivery, although it is intended to be composable with WS-ReliableMessaging; in fact, its intended to be composable with the rest of the WS-* set of specifications... WS-Notification allows the use of a message broker, or a series of connected brokers, as intermediaries between producers and consumers. It Allows the use of proprietary MOM and bridging between proprietary MOM. I encourage you all to go read the spec. Here are some of the interesting items of note: (1) WS-Notification allows for a separate subscription broker that is able to subscribe on behalf of another subscriber. (2) While a 'Notification broker' is part of the spec, it allows for pub/sub to happen directly between the endpoints. The actual sending of the message works similarly. Publishers can send directly to other subscribers, or can send to a Notification Broker and let the Notification Broker take care of getting it to where it needs to go. (3) WS-Notification supports 'demand-based publishing' — Publishers can register with a Notification Broker and inform the broker about the list of topics it intends to publish on. This can be used at least a couple of ways — to authenticate the publisher and apply access control lists to limit the publisher to particular topics. It can also be used as a way for a Notification Broker to be able to manage the topic namespace such that it can apply optimizations such as suspending the publisher when there are no subscribers currently active. (4) The publisher need not be a web service. The publisher may act through a Notification producer which is Web service savvy... [As to] Publishing and Subscribing, WS-Notification supports a hierarchical tree-based topic space (much like SonicMQ). A subscriber can subscribe to entire branches at any level. Hierarchical topic trees allow subscribing to a Topic space that can include any branch in the tree using an Xpath-like 'TopicPathExpression'; security permissions may also be applied using the same mechanism. Publishers and Subscribers are referenced using WS-Addressing Endpoints. Message selectors are also supported using an Xpath-like notation. Message selectors allow a subscriber to filter a message based on a criteria. - There is also the notion of a 'precondition', which is sort of like a 'publish when' a certain condition occurs. Subscriptions may have a InitialTerminationTime, which governs how long the subscription is valid for. The whole lifecycle of resources is governed by a companion spec, WS-ResourceLifeTime..."

• [January 22, 2004] "HP, IBM and Akamai Bring Web Services to Grid Computing." By Jay Lyman. From TechNewsWorld (January 21, 2004). "Rob Batchelder, industry analyst and president of IT consultancy Relevance, said that joining grid computing with Web services makes perfect sense... In an effort to pair and propel two emerging technologies, IBM, HP, Akamai, and other tech companies have proposed new specs to integrate grid computing with Web services. The companies, which announced the new WS-Notification and WS-Resource Framework specs, said the proposed standards represent the first availability of a common, standards-based infrastructure designed for business applications working in conjunction with grid resources... The proposed Web services specifications -- backed by IBM, HP, Akamai, the Globus Alliance, Sonic Software and Tibco -- are intended to define a scalable architecture that has the ability to connect resources (such as servers) to logical constructs (such as business agreements and contracts). The new standard would let customers perform just-in-time procurement with multiple suppliers who all adhere to the same specifications. Plus, the system would allow for grid-based workload balancing and the ability to detect system outages and recover from those outages automatically. One example of the standard in action would be suppliers automatically getting notified to replenish inventory once current inventory drops to a certain level. 'These new Web services specifications will significantly extend the types of enterprise solutions customers can easily deploy,' said IBM director of dynamic e-business technologies Karla Norsworthy. 'These new specifications provide customers with the ability to use a common Web-services-based infrastructure that supports grid- and management-based solutions'... While some observers pointed out that the Web services standards proposed by IBM, HP and the others differ from similar standards advanced by Microsoft and partners, Batchelder said all of the parties promoting Web services realize that 'everybody needs to do this'..." See details in the news story "Web Services Notification and Web Services Resource Framework."

• [January 20, 2004] "WS-Resource Framework:Globus Alliance Perspectives." By Ian Foster [WWW] (Argonne National Laboratory / University of Chicago / Globus Alliance). Presentation January 20, 2004 at GlobusWORLD 2004. See especially slide #9, "From OGSI to WSRF:Refactoring and Evolution." "... Despite enthusiasm for OGSI [Open Grid Services Infrastructure (OGSI) Version 1.0], adoption within Web community turned out to be problematic: Too much stuff in one specification, does not work well with existing Web services tooling, Too 'object oriented'. The solution: WSRF partitions OGSI version 1.0 functionality into a family of composable specifications, tones down the usage of XML Schema, and makes an explicit distinction between the 'service' and the stateful 'resources' acted upon by that service..." [source .PPT, cache]

• [January 20, 2004] "Web Services Notification and Web Services Resource Framework." 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."

• [July 22, 2003] "Web Services and Sessions." By Sergey Beryozkin. In O'Reilly WebServices.xml.com (July 22, 2003). "Web services are becoming an important tool for solving enterprise application and business-to-business integration problems. An enterprise application is usually exposed to the outside world as a single monolithic service, which can receive request messages and possibly return response messages, as determined by some contract. Such services are designed according to the principles of a service-oriented architecture. They can be either stateless or stateful. Stateful services can be useful, for example, for supporting conversational message exchange patterns and are usually instance or session-based, but they are monolithic in the sense that the session instantiation is always implicit. In general, a service-oriented approach (simple interactions, complex messages) may be better suited to building stateful web services, especially in the bigger B2B world, where integration is normally achieved through an exchange of XML documents. Coarse-grained services, with their API expressed in terms of the document exchange, are likely to be more suitable for creating loosely coupled, scalable and easily composable systems. Yet there still exists a certain class of applications which might be better exposed in a traditional session-oriented manner. Sometimes a cleaner design can be achieved by assigning orthogonal sets of functionality to separate services, and using thus simpler XML messages as a result. Such web services are fine-grained... If you believe that for a particular use case a fine grained design can result in a better interface, and that a reasonable compromise with respect to those problems can be achieved, then such a route should at least be explored. It is likely we'll see some standardization efforts in this area of state and resource management in the near future. Meanwhile, this article will look at ways of building stateful web services. In particular we highlight different ways of defining service references and identifying individual sessions..."

• [July 2003] " Web and Grid Services: Architectures and Technologies." By Savas Parastatidis. 43 pages/slides.

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