Proceedings Article•
COBEA: a CORBA-based event architecture
27 Apr 1998-pp 9-9
TL;DR: COBEA is shown to be flexible in supporting various application scenarios yet handles efficiently the most common event communications, and the performance of server-side filtering for various registration scenarios is presented.
Abstract: Events are an emerging paradigm for composing applications in an open, heterogeneous distributed world. In Cambridge we have developed scalable event handling based on a publish-register-notify model with event object classes and server-side filtering based on parameter templates. After experience in using this approach in a home-built RPC system we have extended CORBA, an open standard for distributed object computing, to handle events in this way.
In this paper, we present the design of COBEA - a COrba-Based Event Architecture. A service that is the source of (parameterised) events publishes in a Trader the events it is prepared to notify, along with its normal interface specification. For scalability, a client must register interest (by invoking a register method with appropriate parameters or wild cards) at the service, at which point an access control check is carried out. Subsequently, whenever a matching event occurs, the client is notified.
We outline the requirements on the COBEA architecture, then describe its components and their interfaces. The design and implementation aim to support easy construction of applications by using COBEA components. The components include event primitives, an event mediator and a composite event service; each features well-defined interfaces and semantics for event registration, notification and filtering. We demonstrate that COBEA is flexible in supporting various application scenarios yet handles efficiently the most common event communications. The performance of server-side filtering for various registration scenarios is presented. Our initial experience with applications is also described.
Citations
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02 Jul 2002
TL;DR: Her Hermes, a novel event-based distributed middleware architecture that follows a type- and attribute-based publish/subscribe model that centres around the notion of an event type and supports features commonly known from object-oriented languages like type hierarchies and super-type subscriptions is introduced.
Abstract: In this paper, we argue that there is a need for an event-based middleware to build large-scale distributed systems. Existing publish/subscribe systems still have limitations compared to invocation-based middlewares. We introduce Hermes, a novel event-based distributed middleware architecture that follows a type- and attribute-based publish/subscribe model. It centres around the notion of an event type and supports features commonly known from object-oriented languages like type hierarchies and super-type subscriptions. A scalable routing algorithm using an overlay routing network is presented that avoids global broadcasts by creating rendezvous nodes. Fault-tolerance mechanisms that can cope with different kinds of failures in the middleware are integrated with the routing algorithm resulting in a scalable and robust system.
566 citations
Cites methods from "COBEA: a CORBA-based event architec..."
...We first present the algorithm implemented by the type-based pub/sub layer which disseminates events solely based on their type, and then outline the extensions by the type- and attribute-based pub/sub layer that supports content-based filtering....
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09 Oct 1997
TL;DR: This paper describes the design and performance of an object-oriented, real-time implementation of the GORBA Event Service that is designed to meet these requirements and presents benchmarks that demonstrate the performance tradeoffs of alternative concurrent dispatching mechanisms for real- time Event Services.
Abstract: The CORBA Event Service provides a flexible model for asynchronous communication among objects. However, the standard CORBA Event Service specification lacks important features required by real-time applications. For instance, operational flight programs for fighter aircraft have complex real-time processing requirements. This paper describes the design and performance of an object-oriented, real-time implementation of the GORBA Event Service that is designed to meet these requirements.This paper makes three contributions to the design and performance measurement of object-oriented real-time systems. First, it illustrates how to extend the CORBA Event Service so that it is suitable for real-time systems. These extensions support periodic rate-based event processing and efficient event filtering and correlation. Second, it describes how to develop object-oriented event dispatching and scheduling mechanisms that can provide real-time guarantees. Finally, the paper presents benchmarks that demonstrate the performance tradeoffs of alternative concurrent dispatching mechanisms for real-time Event Services.
442 citations
Cites methods from "COBEA: a CORBA-based event architec..."
...Other research on the CORBA Event Service [25, 26] describe techniques for optimizing event service performance for filtering and message delivery....
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Journal Article•
TL;DR: Cooperative Information Systems (CoopIS) 2004 International Conference (International Conference on Cooperative Information Systems) PC Co-chairs' Message- Keynote- Business Process Optimization- Workflow/Process/Web Services, I- Discovering Workflow Transactional behavior from Event-based Log- A Flexible Mediation Process for Large Distributed Information Systems- Exception Handling Through a Workflow- WorkFlow/Process, Web Services, II- Flexible and Composite Schema Matching Algorithm- Analysis, Transformation, and Improvements of ebXML Choreographies based on Work
Abstract: Cooperative Information Systems (CoopIS) 2004 International Conference- CoopIS 2004 International Conference (International Conference on Cooperative Information Systems) PC Co-chairs' Message- Keynote- Business Process Optimization- Workflow/Process/Web Services, I- Discovering Workflow Transactional Behavior from Event-Based Log- A Flexible Mediation Process for Large Distributed Information Systems- Exception Handling Through a Workflow- Workflow/Process/Web Services, II- A Flexible and Composite Schema Matching Algorithm- Analysis, Transformation, and Improvements of ebXML Choreographies Based on Workflow Patterns- The Notion of Business Process Revisited- Workflow/Process/Web Services, III- Disjoint and Overlapping Process Changes: Challenges, Solutions, Applications- Untangling Unstructured Cyclic Flows - A Solution Based on Continuations- Making Workflow Models Sound Using Petri Net Controller Synthesis- Database Management/Transaction- Concurrent Undo Operations in Collaborative Environments Using Operational Transformation- Refresco: Improving Query Performance Through Freshness Control in a Database Cluster- Automated Supervision of Data Production - Managing the Creation of Statistical Reports on Periodic Data- Schema Integration/Agents- Deriving Sub-schema Similarities from Semantically Heterogeneous XML Sources- Supporting Similarity Operations Based on Approximate String Matching on the Web- Managing Semantic Compensation in a Multi-agent System- Modelling with Ubiquitous Agents a Web-Based Information System Accessed Through Mobile Devices- Events- A Meta-service for Event Notification- Classification and Analysis of Distributed Event Filtering Algorithms- P2P/Collaboration- A Collaborative Model for Agricultural Supply Chains- FairNet - How to Counter Free Riding in Peer-to-Peer Data Structures- Supporting Collaborative Layouting in Word Processing- A Reliable Content-Based Routing Protocol over Structured Peer-to-Peer Networks- Applications, I- Covering Your Back: Intelligent Virtual Agents in Humanitarian Missions Providing Mutual Support- Dynamic Modelling of Demand Driven Value Networks- An E-marketplace for Auctions and Negotiations in the Constructions Sector- Applications, II- Managing Changes to Engineering Products Through the Co-ordination of Human and Technical Activities- Towards Automatic Deployment in eHome Systems: Description Language and Tool Support- A Prototype of a Context-Based Architecture for Intelligent Home Environments- Trust/Security/Contracts- Trust-Aware Collaborative Filtering for Recommender Systems- Service Graphs for Building Trust- Detecting Violators of Multi-party Contracts- Potpourri- Leadership Maintenance in Group-Based Location Management Scheme- TLS: A Tree-Based DHT Lookup Service for Highly Dynamic Networks- Minimizing the Network Distance in Distributed Web Crawling- Ontologies, DataBases, and Applications of Semantics (ODBASE) 2004 International Conference- ODBASE 2004 International Conference (Ontologies, DataBases, and Applications of Semantics) PC Co-chairs' Message- Keynote- Helping People (and Machines) Understanding Each Other: The Role of Formal Ontology- Knowledge Extraction- Automatic Initiation of an Ontology- Knowledge Extraction from Classification Schemas- Semantic Web in Practice- Generation and Management of a Medical Ontology in a Semantic Web Retrieval System- Semantic Web Based Content Enrichment and Knowledge Reuse in E-science- The Role of Foundational Ontologies in Manufacturing Domain Applications- Intellectual Property Rights Management Using a Semantic Web Information System- Ontologies and IR- Intelligent Retrieval of Digital Resources by Exploiting Their Semantic Context- The Chrysostom Knowledge Base: An Ontology of Historical Interactions- Text Simplification for Information-Seeking Applications- Information Integration- Integration of Integrity Constraints in Federated Schemata Based on Tight Constraining- Modal Query Language for Databases with Partial Orders- Composing Mappings Between Schemas Using a Reference Ontology- Assisting Ontology Integration with Existing Thesauri
284 citations
Book•
09 Jun 2000
TL;DR: This book provides a conceptual framework within which to describe object-oriented middleware for the integration of distributed objects and UML is used to explain distributed systems concepts.
Abstract: The pay-offs for creating distributed applications are in achieving portability, scalability and fault-tolerance. In order to simplify building software that performs robustly regardless of platform or network infrastructure, a new strata of middleware has been created. This book provides a conceptual framework within which to describe object-oriented middleware for the integration of distributed objects. UML is used to explain distributed systems concepts. Presenting both an extended case study and smaller illustrative examples, there are plenty of coded examples in Java, C++, CORBA IDL and Microsoft IDL, which reflect the reality of todays multi-language heterogeneous systems. This is a book for developers who are new to programming in distributed environments. It also supports a variety of courses where the central theme is object-oriented development with middleware technologies. The book shows the middleware concepts and principles using examples taken from: OMG/CORBA Microsoft COM Java/RMI On the accompanying website are exercises, sample solutions and working code for the examples. This site is also designed for instructors to assist them with course development and delivery.
224 citations
Dissertation•
22 Nov 2002
TL;DR: This thesis concentrates on mechanisms to improve the scalability of content-based routing algorithms and presents more advanced routing algorithms that do not rely on global knowledge and the idea of imperfect routing algorithms is introduced.
Abstract: Today, the architecture of distributed computer systems is dominated by client/server platforms relying on synchronous request/reply. This architecture is not well suited to implement information-driven applications like news delivery, stock quoting, air traffic control, and dissemination of auction bids due to the inherent mismatch between the demands of these applications and the characteristics of those platforms. In contrast to that, publish/subscribe directly reflects the intrinsic behavior of information-driven applications because communication here is indirect and initiated by producers of information: Producers publish notifications and these are delivered to subscribed consumers by the help of a notification service that decouples the producers and the consumers. Therefore, publish/subscribe should be the first choice for implementing such applications. The expressiveness of the notification selection mechanism used by the consumers to describe the notifications they are interested in is crucial for the flexibility of a notification service. Content-based notification selection is most expressive because it allows to evaluate filter predicates over the whole content of a notification. The advantage in expressiveness compared to channel- or subject-based selection results in increased flexibility facilitating extensibility and change. On the other hand, scalable implementations of content-based notification services are difficult to realize. Indeed, the expressiveness of notification selection must be carefully chosen in large-scale systems, because expressiveness and scalability are interdependent. Hence, the most fundamental problem in the area of content-based publish/subscribe systems is probably the scalable routing of notifications from their producers to their respective consumers. Unfortunately, existing content-based notification services are not mature enough to be used in large-scale, widely-distributed environments. Most existing notification services are either centralized, use flooding, or use simple routing algorithms that assume that each event broker has global knowledge about all active subscriptions. All these approaches exhibit severe scalability problems in large-scale systems. In contrast to that, this thesis concentrates on mechanisms to improve the scalability of content-based routing algorithms and presents more advanced routing algorithms that do not rely on global knowledge. The algorithms presented here exploit similarities between subscriptions by using identity- and covering-tests, and by merging filters. While identity-based routing is a simplified version of covering-based routing, merging-based routing is more advanced because it exploits the concept of filter merging. Furthermore, the idea of imperfect routing algorithms is introduced. The thesis consists of a theoretical and a practical part. The theoretical part presents a formal specification of publish/subscribe systems, a routing framework and a set of routing algorithms, and discusses how the routing optimizations can be broken down to the actual data/filter model. The practical part presents the implementation of the Rebeca notification service which supports advertisements and all the routing algorithms mentioned above. A detailed practical evaluation of the implemented algorithms based upon the prototype is also presented.
223 citations
References
More filters
09 Oct 1997
TL;DR: This paper describes the design and performance of an object-oriented, real-time implementation of the GORBA Event Service that is designed to meet these requirements and presents benchmarks that demonstrate the performance tradeoffs of alternative concurrent dispatching mechanisms for real- time Event Services.
Abstract: The CORBA Event Service provides a flexible model for asynchronous communication among objects. However, the standard CORBA Event Service specification lacks important features required by real-time applications. For instance, operational flight programs for fighter aircraft have complex real-time processing requirements. This paper describes the design and performance of an object-oriented, real-time implementation of the GORBA Event Service that is designed to meet these requirements.This paper makes three contributions to the design and performance measurement of object-oriented real-time systems. First, it illustrates how to extend the CORBA Event Service so that it is suitable for real-time systems. These extensions support periodic rate-based event processing and efficient event filtering and correlation. Second, it describes how to develop object-oriented event dispatching and scheduling mechanisms that can provide real-time guarantees. Finally, the paper presents benchmarks that demonstrate the performance tradeoffs of alternative concurrent dispatching mechanisms for real-time Event Services.
442 citations
"COBEA: a CORBA-based event architec..." refers background in this paper
...Some domain speci c issues such as real-time issues described by [7] are not particularly addressed by COBEA....
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...Some real-time issues are discussed in [7]....
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...Work in real-time event noti cation [7, 19] has produced useful designs and implementations which use real-time threads for event publication in order to prevent priority inversion....
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...Architectural frameworks for event handling in large distributed systems are discussed in [2, 7, 14, 19, 23, 24, 25]....
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...Some recent work and products [7, 18, 10] have extended it; Expersoft, Iona, Sun Systems and Visigenic Software have developed commercial CORBA-compliant event services....
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01 Jun 1992
TL;DR: Several examples of work to allow physically separated colleagues to work together effectively and naturally are discussed in the context of three themes that have emerged: the need to support the full range of shared work; the desire to ensure privacy without giving up unobtrusive awareness; and the possibility of creating systems which blur the boundaries between people, technologies and the everyday world.
Abstract: At EuroPARC, we have been exploring ways to allow physically separated colleagues to work together effectively and naturally. In this paper, we briefly discuss several examples of our work in the context of three themes that have emerged: the need to support the full range of shared work; the desire to ensure privacy without giving up unobtrusive awareness; and the possibility of creating systems which blur the boundaries between people, technologies and the everyday world.
438 citations
01 Apr 1993
TL;DR: This paper investigates the definition, detection, and management of events in the active object-oriented database system SAMOS, and presents various event specification facilities based on simple but nevertheless powerful constructs which support the modelling of time aspects.
Abstract: In this paper we investigate the definition, detection, and management of events in the active object-oriented database system SAMOS. First, we present various event specification facilities based on simple but nevertheless powerful constructs which support the modelling of time aspects as well. Second we show how events can be detected in an efficient way. Finally, we deal with the internal representation of events using the benefits of the underlying data model.
290 citations
"COBEA: a CORBA-based event architec..." refers background or methods in this paper
...Active systems monitor the occurrences of events and push them through to client applications to trigger actions [2, 5]....
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...Related work such as the ECA (Event-Condition-Action) rules in active databases [4, 5, 22] uses conditions...
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...Work in active databases is of direct relevance to the research on active systems [4, 5, 22]....
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15 May 1995
TL;DR: The real-time publisher/subscriber model as discussed by the authors is a variation of group-based programming and anonymous communication techniques, which can address issues of programming ease, portability, scalability and analyzability.
Abstract: Distributed real-time systems are becoming more pervasive in many domains including process control, discrete manufacturing, defense systems, air traffic control, and online monitoring systems in medicine. The construction of such systems, however, is impeded by the lack of simple yet powerful programming models and the lack of efficient, scalable, dependable and analyzable interfaces and their implementations. We argue that these issues need to be resolved with powerful application-level toolkits similar to that provided by ISIS. We consider the inter-process communication requirements which form a fundamental block in the construction of distributed real-time systems. We propose the real-time publisher/subscriber model, a variation of group-based programming and anonymous communication techniques, as a model for distributed real-time inter-process communication which can address issues of programming ease, portability, scalability and analyzability. The model has been used successfully in building a software architecture for building upgradable real-time systems. We provide the programming interface, a detailed design and implementation details of this model along with some preliminary performance benchmarks. The results are encouraging in that the goals we seek look achievable.
174 citations
05 Jun 1995
TL;DR: In this paper, an Interface Definition Language (IDLDL) is extended to handle event registration and notification, and a composite event recogniser based on non-deterministic finite state machines is implemented.
Abstract: We have extended an Interface Definition Language to handle event registration and notification. Clients register interest in specified classes of events and servers then notify them of any occurrence asynchronously. Event occurrences are identified by parameters which conform to IDL typing constraints and can therefore be used in synchronous method invocations. Methods to handle registration and notification are generic and can be inherited by objects of any class: as a by-product of IDL processing the stubs to handle event creation and decoding are generated automatically. We have implemented a prototype composite event recogniser based on non-deterministic finite state machines. Initial experience with this prototype is encouraging. >
124 citations