Um monitor de metadados de QoS e QoC para plataformas de middleware

Context-aware applications are typically dynamic and use services provided by several sources, with different quality levels. Context information qualities are expressed in terms of Quality of Context (QoC) metadata, such as precision, correctness, refreshment, and resolution. On the other hand, service qualities are expressed via Quality of Services (QoS) metadata such as response time, availability and error rate. In order to assure that an application is using services and context information that meet its requirements, it is essential to continuously monitor the metadata. For this purpose, it is needed a QoS and QoC monitoring mechanism that meet the following requirements: (i) to support measurement and monitoring of QoS and QoC metadata; (ii) to support synchronous and asynchronous operation, thus enabling the application to periodically gather the monitored metadata and also to be asynchronously notified whenever a given metadata becomes available; (iii) to use ontologies to represent information in order to avoid ambiguous interpretation. This work presents QoMonitor, a module for QoS and QoC metadata monitoring that meets the abovementioned requirement. The architecture and implementation of QoMonitor are discussed. To support asynchronous communication QoMonitor uses two protocols: JMS and Light-PubSubHubbub. In order to illustrate QoMonitor in the development of ubiquitous application it was integrated to OpenCOPI (Open COntext Platform Integration), a Middleware platform that integrates several context provision middleware. To validate QoMonitor we used two applications as proofof- concept: an oil and gas monitoring application and a healthcare application. This work also presents a validation of QoMonitor in terms of performance both in synchronous and asynchronous requests