In this paper, we provide preliminary results on the emerging problem of modeling and managing uncertainty in concurrent database transactions. This work thus completes several previous studies that, by the contrary, have not considered the specific case of concurrent transactions, which may worse the uncertainty of database management activities beyond to the simplest case of isolated transactions. Indeed, as we demonstrate in this paper, inconsistency tolerance of integrity management, constraint checking and repairing easily scales up to concurrent transactions in a natural way, and query answering in concurrent transactions over uncertain data remains certain in the presence of uncertainty

Integrity Maintenance includes integrity checking and repairing. Checking updates for integrity prevents an increase of inconsistency, repairing decreases inconsistency. Both can be supported by inconsistency metrics. We improve their axiomatization, which, so far, has been elusive and inappropriate for databases with non-monotonic negation.

All methods for efficient integrity checking require all integrity constraints to be totally satisfied, before any update is executed. However, a certain amount of inconsistency is the rule, rather than the exception in databases. In this paper, we close the gap between theory and practice of integrity checking, i.e., between the unrealistic theoretical requirement of total integrity and the practical need for inconsistency tolerance, which we define for integrity checking methods. We show that most of them can still be used to check whether updates preserve integrity, even if the current state is inconsistent. Inconsistency-tolerant integrity checking proves beneficial both for integrity preservation and query answering. Also, we show that it is useful for view updating, repairs, schema evolution, and other applications.

We define and examine six classes of methods for integrity checking: case-based, compositional, relevance-based, simplification-based, total-integrity-dependent, and measure-based ones. Each, except the penultimate, corresponds to a particular form of inconsistency tolerance. Inconsistency measures provide a new approach to integrity checking and inconsistency tolerance. For many methods, proofs or disproofs of their inconsistency tolerance become easier and more transparent by our classification. In general, a better understanding of inconsistency-tolerant integrity checking is achieved

Passive replication has been extensively studied in the literature. However, there is no comprehensive study yet with regard to its degree of communication synchrony. Therefore, we propose a new, detailed classification of hot passive replication protocols, including a survey of the fault tolerance and performance of each class

Mobile databases are a centerpiece of the dramatic growth of data-centric applications for mobile computing, nomadic communication and wireless networks. Replication of database content is useful in client-server and peer- to-peer configurations of mobile distributed databases. We present an adaptation of generalized snapshot isolation for transactions on content data in mobile networks. This solution overcomes various limitations of known approaches to manage mobile database transactions.

Database replication protocols need to detect, block or abort part of conflicting transactions. A possible solution is to check their writesets (and also their readsets in case a serialisable isolation level is requested), which however burdens the consumption of CPU time. This gets even worse when the replication support is provided by a middleware, since there is no direct DBMS support in that layer. We propose and discuss the use of the concurrency control support of the local DBMS for detecting conflicts between local transactions and writesets of remote transactions. This allows to simplify many database replication protocols and to enhance their performance

The main objective of the EU-promoted project MOVE (Mobile Middleware with Voice-Enabled Services, http://move.rwth-aachen.de) was the integration of voice (real-time data) and multimedia services (non-real-time data) for mobile GSM- and UMTS-based communication, transmitted via the Internet Protocol. An architecture was developed which was enhanced with an API for service providers. It permits the initiation, maintenance and termination of voice-enabled multimedia connections from an Internet site via a single link, such as collaborative Web surfing in a phone conference. Real-time voice or video streams are decoded according to the transmission quality for real-time streams. They are transmitted with high priority, relative to non-real-time data which are downsized, if necessary. Special attention is paid to the monitoring and adaptation of heterogeneous media streams concerning their adjustment to a wide range of quality-of-service parameters.

For each view predicate, a Transaction Tree (T-tree) can be derived from a database schema. T-trees are data structures which serve to anticipate transactions by which view update requests can be translated to updates of underlying base relations. Since T-trees are obtained at schema specification time, i.e. in advance of update time, they provide a basis for planning strategies with which appropriate transactions can be chosen to satisfy view update requests, and also for strategies which support schema evolution. The main features of the approach are that it is simple, it offers solutions to the problem of missing values, it is correct and it is complete (in the case of nonrecursive views).

We compare and synthesize different methods for integrity checking in deductive databases. First, we state simplified integrity checking for deductive databases independently of the particular strategy used by different methods found in the literature. In accordance with this statement, we classify integrity checking methods into two main groups: methods with a generation phase without fact access and methods with a generation phase with fact access. Then, we propose an implementation scheme (a metaprogram) where the differences and similarities among the methods can be pointed out. In this common implementation framework, we compare the methods; this comparison is based on the number of facts accessed by each of them during integrity checking. Finally and from the analysis of the results, we define a convergence method which synthesizes some different features from several methods.>