A Transaction Model for Executions of Compositions of Internet of Things Services

AbstractInternet of Things (IoT) is about making “things” smart in some functionality, and connecting and enabling them to perform complex tasks by themselves. The functionality can be encapsulated as services and the task executed by composing the services. Two noteworthy functionalities of IoT services are monitoring and actuation. Monitoring implies continuous executions, and actuation is by triggering. Continuous executions typically involve stream processing. Stream input data are accumulated into batches and each batch is subjected to a sequence of computations, structured as a dataflow graph. The composition may be processing several batches simultaneously. Additionally, some non-stream OLTP transactions may also be executing concurrently. Thus, several composite transactions may be executing concurrently. This is in contrast to a typical Web services composition, where just one composite transaction is executed on each invocation. Therefore, defining transactional properties for executions of IoT service compositions is much more complex than for those of conventional Web service compositions. In this paper, we propose a transaction model and a correctness criterion for executions of IoT service compositions. Our proposal defines relaxed atomicity and isolation properties for transactions in a flexible manner and can be adapted for a variety of IoT applications

On Atomic Batch Executions in Stream Processing

AbstractStream processing is about processing continuous streams of data by programs in a workflow. Continuous execution is discretized by grouping input stream tuples into batches and using one batch at a time for the execution of programs. As source input batches arrive continuously, several batches may be processed in the workflow simultaneously. A general requirement is that each batch be processed completely in the workflow. That is, all the programs triggered by the batch, directly and transitively, in the workflow must be executed successfully. Executing only a prefix of the workflow amounts to dropping (discarding) the batches that were derived by the executed part and were supposed to be input to the rest of the workflow. In some cases, such partial executions may not be acceptable and may have to be rolled back, amounting to dropping the source input batches that were processed by the partial execution. We refer to this property of processing the batches either completely or not at all as atomic execution of the batches. We also attribute the property to the batches themselves, calling them atomic batches, meaning that the property applies to the set of transactions that are executed due to that batch. If batches are processed in isolation in the workflow, preserving atomicity is fairly straightforward. When batches are split or merged along the workflow computation, the problem becomes complicated. In this paper, we study issues relating to the atomicity of batches. We illustrate that, in general, preserving atomicity of some batches may affect the atomicity of some other batches, and suggest trade-offs

Capability-based resiliency control of distributed database systems

It is highly desirable for a distributed database system to achieve logically continuous operation even if some sites or message links fail. In this paper, we describe a scheme that can automati­cally reconfigure a fully-replicated distributed database system upon subsystem failures. The scheme can tolerate total failures of some sites. That is, some sites may lose their data completely including backup data. In order to handle this problem, we divide the execution of the system into generations. Each generation starts with a consistent database state and ends with a consistent database state. Serial­izability of the execution of each generation is enforced by con­currency control based on conditional capabilities. Conditional capabilities are valid only if they are being endorsed by a majority of sites in the system. Thus, any majority set of sites can invali­date lost or stray capabilities of old generations, and they can newly create capabilities for a new generation. Therefore, as long as there exist a majority of working sites that belong to the same partition, the system can continue its operation. The scheme allows a system to be reconfigured even if some transactions are being pro­cessed and even if other system reconfiguration attempts are under­way.Key Words and Phrases: distributed database system, resiliency con­trol, consistent database state, replicated data, conditional capa­bilitie

Electrochemically synthesized polymers in molecular imprinting for chemical sensing

This critical review describes a class of polymers prepared by electrochemical polymerization that employs the concept of molecular imprinting for chemical sensing. The principal focus is on both conducting and nonconducting polymers prepared by electropolymerization of electroactive functional monomers, such as pristine and derivatized pyrrole, aminophenylboronic acid, thiophene, porphyrin, aniline, phenylenediamine, phenol, and thiophenol. A critical evaluation of the literature on electrosynthesized molecularly imprinted polymers (MIPs) applied as recognition elements of chemical sensors is presented. The aim of this review is to highlight recent achievements in analytical applications of these MIPs, including present strategies of determination of different analytes as well as identification and solutions for problems encountered

Supporting process control in business collaborations

Business collaborations have become highly dynamic and flexible. "Black-box" services are gradually replaced by services where service providers not only expose the underlying processes but also allow some monitoring of their executions. In this paper, we explore the next step where the consumers can exercise some control over the process execution. We specify a set of control primitives that can be used to exert control on activities before, during and after their execution and on the complete process itself. Our design approach allows the consumer to observe the state of execution of the process and its activities, control their execution and decide how to deal with unsuccessful executions. We describe the support that must be provided in the internal process specification of the service provider for the control options. We illustrate our approach with an example from the healthcare domain

Enhancing business collaborations with client-oriented process control

Nowadays, business collaborations have to be highly dynamic and flexible to allow companies to operate efficiently and effectively in complex and volatile markets. To increase the business agility of service consumers, it is fundamental that service providers enhance the visibility of parts of their collaborative processes. Service providers are required to release both the process structures of the services offered and their status during execution. To further increase the flexibility of business collaborations, certain control over the process execution has to be offered to service consumers. In this paper, we present a framework for the support of process control in cross-organizational settings. We specify the control primitives that can be used to exert control on activities and processes before, during and after their executions. These primitives empower service consumers to postpone activity and process executions, bypass minor activities, repeat their executions, etc. We describe an approach to the support of these control primitives by service providers. We demonstrate the application of our framework with a case study from the healthcare domain. A proof-of-concept prototype implementation based on Web service technology is presented