The paper presents a service composition language called VINCA, which differs from many existing ones in its emphasis on enabling business users to visually "program" from business view-point their personalized applications on the basis of Web-based services. VINCA embodies an integrated approach to mediating between diverse, rapidly changing user requirements and composites of individual services scattered over the Internet. The approach is targeted at application scenarios that require Web-based services be quickly assembled by non-computer professionals to fulfill certain spontaneous requirements. VINCA is developed within a real-world project for developing a service mediation platform for the Olympic Games Beijing 2008, on which an effective information system providing personalized and one-stop information services to the general public, should be based. In this paper, we introduce the main features and design rationales of VINCA with a scenario, and also discuss its implementation and application.
Mobile devices such as personal digital assistants (PDAs) and mobile phones are in widespread use already today and converging to mobile smart phones. They enable users to access a wide range of services and information without guidance through their actual demands. Especially during mass events like the Olympic Games 2008 in BeijingVwhich was initially the context of our workVa large service space is expected to support all mobile visitors, being athletes, journalists, or spectators. Current approaches tackling such problems are location based, meaning that a user's location is central to service provision, and even context-aware, meaning that, beyond location, characteristics of a user's environment are taken into account. Such information obviously helps to deliver relevant information at the right time to the mobile users. Going one step further, a situation-aware system abstracts from the context dimensions by translating specific contexts into logical situations. Knowing the situation end users are in allows the system to better identify the information to be delivered to them and to choose the appropriate services with regard to their scope, which is referred to as service roaming. Even though many context frameworks have been introduced in the past few years, what is usually missing is the notion of characteristic features of contexts that are invariant during certain time intervals. This paper presents these concepts in the context of a platform development, namely FLAME2008, which is able to support its mobile users with personalized situation-aware services in push and pull mode.
Federated transaction management (also known as multidatabase transaction management in the literature) is needed to ensure the consistency of data that is distributed across multiple, largely autonomous, and possibly heterogeneous component databases and accessed by both global and local transactions. While the global atomicity of such transactions can be enforced by using a standardized commit protocol like XA or its CORBA counterpart OTS, global serializability is not self-guaranteed as the underlying component systems may use a variety of potentially incompatible local concurrency control protocols. The problem of how to achieve global serializability, by either constraining the component systems or implementing additional global protocols at the federation level, has been intensively studied in the literature, but did not have much impact on the practical side. A major deficiency of the prior work has been that it focused on the idealized correctness criterion of serializability and disregarded the subtle but important variations of SQL isolation levels supported by most commercial database systems. This paper reconsiders the problem of federated transaction management, more specifically its concurrency control issues, with particular focus on isolation levels used in practice, especially the popular snapshot isolation provided by Oracle. As pointed out in a SIGMOD 1995 paper by Berenson et al., a rigorous foundation for rea-soning about such concurrency control features of commercial systems is sorely missing. The current paper aims to close this gap by developing a formal framework that allows us to reason about local and global transaction executions where some (or all) transactions are run under snapshot isolation. The paper derives criteria and prac-tical protocols for guaranteeing global snapshot isolation at the federation level. It further generalizes the well-known ticket method to cope with combinations of isolation levels in a federated system
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