Automating Fine Concurrency Control in Object-Oriented Databases

Several propositions were done to provide adapted concurrency control to object-oriented databases. However, most of these proposals miss the fact that considering solely read and write access modes on instances may lead to less parallelism than in relational databases! This paper cope with that issue, and advantages are numerous: (1) commutativity of methods is determined a priori and automatically by the compiler, without measurable overhead, (2) run-time checking of commutativity is as efficient as for compatibility, (3) inverse operations need not be specified for recovery, (4) this scheme does not preclude more sophisticated approaches, and, last but not least, (5) relational and object-oriented concurrency control schemes with read and write access modes are subsumed under this proposition

Speculative Concurrency Control for Real-Time Databases

In this paper, we propose a new class of Concurrency Control Algorithms that is especially suited for real-time database applications. Our approach relies on the use of (potentially) redundant computations to ensure that serializable schedules are found and executed as early as possible, thus, increasing the chances of a timely commitment of transactions with strict timing constraints. Due to its nature, we term our concurrency control algorithms Speculative. The aforementioned description encompasses many algorithms that we call collectively Speculative Concurrency Control (SCC) algorithms. SCC algorithms combine the advantages of both Pessimistic and Optimistic Concurrency Control (PCC and OCC) algorithms, while avoiding their disadvantages. On the one hand, SCC resembles PCC in that conflicts are detected as early as possible, thus making alternative schedules available in a timely fashion in case they are needed. On the other hand, SCC resembles OCC in that it allows conflicting transactions to proceed concurrently, thus avoiding unnecessary delays that may jeopardize their timely commitment

Critical review of literature on the use of short implants

Aim The aims of this review were to verify the validity of short implants as a treatment option in patients with partial or total edentulism, having more or less atrophic jawbones. Methods A systematic review of randomized controlled trials (RCT) was conducted, involving also prospective and retrospective studies published in English language between January 2005 and December 2015. The PubMed and Scopus databases were electronically analyzed. Titles and abstracts were selected, and full texts were evaluated. The data were organized in tables and then presented as a narrative analysis. Results The electronic search provided 891 publications, 50 articles were retrieved in full text and only 11 were included in the review. Although the performance of the implants was evaluated through different success and survival criteria, short implants have shown to have a similar performance to longer implants. Conclusions Short implants could be considered as a treatment option comparable to traditional lenght implant. However, other studies must be conducted to assess uniform criteria to state the quality of treatment

Building a generalized distributed system model

A modeling tool for both analysis and design of distributed systems is discussed. Since many research institutions have access to networks of workstations, the researchers decided to build a tool running on top of the workstations to function as a prototype as well as a distributed simulator for a computing system. The effects of system modeling on performance prediction in distributed systems and the effect of static locking and deadlocks on the performance predictions of distributed transactions are also discussed. While the probability of deadlock is considerably small, its effects on performance could be significant