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Service Oriented Sensor Web. Xingchen Chu and Rajkumar Buyya University of Melbourne, Australia Presented by: Gerardo I. Simari CMSC828P – Fall 2006 Professor Nick Roussopoulos Department of Computer Science University of Maryland College Park, USA. Introduction.

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Service Oriented Sensor Web

Xingchen Chu and Rajkumar Buyya

University of Melbourne, Australia

Presented by: Gerardo I. Simari

CMSC828P – Fall 2006

Professor Nick Roussopoulos

Department of Computer Science

University of Maryland College Park, USA

introduction
Introduction
  • Current sensor nodes are more sophisticated in terms of CPU, memory, and wireless transceiver.
  • Sensor networks are long running systems that consist of sensing nodes that work together to collect data (light, temperature, images, etc).
  • Common applications are real-time detection and early warning systems (fires, tsunamis, earthquakes).
  • The challenge: collection and analysis of information from heterogeneous nodes.
why is this a challenge
Why is this a challenge?
  • There is a lack of uniform operations and standard representation for sensor data.
  • There exists no means for resource reallocation and resource sharing.
  • Deployment and usage of resources is usually tightly coupled with the specific location, application, and devices employed.
  • The Service Oriented Architecture (SOA) is an approach to describe, discover, and invoke services from heterogeneous platforms.
  • Here, the term “service” is used both for software and hardware.
soa and sensors
SOA and Sensors
  • Applying the idea of SOA to sensor networks presents sensors as reusable resources which can be discoverable, accessible, and even controlled through the WWW.
  • It also allows to link distributed resources in order to create a sensor grid, enabling the advantages of a computational grid.
  • The main goal of the Sensor Web (SW) is to offer reliable and accessibleservices to end users.
  • The following figure illustrates an abstract vision of the SW, a combination of SOA, grid computing, and sensor networks.
sensor web enablement
Sensor Web Enablement
  • A set of web-based services may be used to maintain a registry of available sensors.
  • The same web technology standard for describing the sensors’ outputs, platforms, locations, and control parameters should be used all across.
  • This enables the necessary interoperability.
  • The Open Geospatial Consortium (OGC) developed the Sensor Web Enablement (SWE) standard.
  • This standard encompasses specifications for interfaces, protocols, and encodings that enable the use of sensor data and services.
sensor web enablement1
Sensor Web Enablement
  • The following are the five specifications for SWE:
    • Sensor Model Language (SensorML): Information model and XML encodings.
    • Observation and Measurement (O&M): Information model and XML encodings.
    • Sensor Collection Service (SCS): Service to fetch observations; also uses SensorML to describe sensor platforms.
    • Sensor Planning Service (SPS): Helps users build feasible sensor collection plans, and schedule requests for sensor platforms.
    • Web Notification Service (WNS): Manages client sessions and notifies about outcomes of requests.
sensorml
SensorML
  • SensorML is an XML encoding scheme that allows clients to remotely use real-time data from web-resident sensors.
  • A standard format for sensor information enables integration, analysis, and creation of data views depending on the user.
  • It also benefits the integration of heterogeneous sensors and platforms, providing an integrated view.
  • It describes the geometric, dynamic, and observational features of sensors.
  • The following figure shows the structure of the Sensor Model Language (SensorML).
observation and measurement
Observation and Measurement
  • O&M is another standard information model and XML encoding.
  • It is required for the Sensor Collection Service and related components of the OGC SWE.
  • The aim is towards defining terms used for measurements, and the relationships between them.
  • The following figure shows the basic observation structure.
swe services
SWE Services
  • SWE defines several standard services that can be used to collaborate with sensor networks.
  • As we mentioned before, SWE contains three service specifications:
    • Sensor Collection Service (SCS)
    • Sensor Planning Service (SPS)
    • Web Notification Service (WNS)
  • There are also two new services: Sensor Alarm Service, and TransducerML.
  • The paper only covers the basic three mentioned above.
swe services cont
SWE Services (cont.)
  • SCS is used to fetch observations from a sensor or collection of sensors.
  • It plays the role of intermediary agent between a client and an observation repository or near real-time sensor channel.
  • It responds to queries from the client with XML data conformed to the O&M model.
  • SPS provides a standard interface to handle asset management (AM) that manages information sources to meet the client’s goals.
  • It plays a role of coordinator responsible for evaluating the feasibility of the request and submitting the query to the SCS.
swe services cont1
SWE Services (cont.)
  • The WNS is an asynchronous messaging service.
  • Sending and receiving notifications are the main responsibilities of the WNS, utilizing various communication protocols (HTTP POST, email, SMS, instant message, phone, fax, etc).
  • Operations are defined to conduct both one-way and two-way communication between users and services.
service oriented sensor web
Service Oriented Sensor Web
  • Open Source Web Architecture (OSWA) is an SWE compliant infrastructure for providing service oriented access and management of sensors.
  • It’s a platform for integrating sensor networks and distributed computing platforms such as SOA.
  • Among the benefits, the heavy information processing load can be moved to backend distributed systems such as grids.
  • This can save a lot of energy in the sensor networks, and accelerate the processing.
  • Individual sensor networks can be linked together as services.
the oswa platform
The OSWA Platform
  • Fundamental services are provided by low-level components, whereas high-level components provide tools for creating applications.
  • The OSWA platform provides services such as:
    • Sensor notification, collection, and observation
    • Data collection, aggregation, and archive
    • Sensor coordination and data processing
    • Faulty sensor data correction and management
    • Sensor configuration and directory service
  • The OSWA focuses on providing an interactive development environment, a middleware and coordination language for developing sensor apps.
design and implementation
Design and Implementation
  • The primary design and implementation of OSWA focuses on its core services (SCS, WNS, and SPS),
  • The Sensory Repository Service is also key, providing the persistent mechanism for sensor and observation data.
  • In the following figure, we show a typical client collection request, and the invocations between relating services.
  • We will then discuss the design and implementation of each of the core services in turn.
sensor collection service
Sensor Collection Service
  • SCS is one of the most important components residing in the service layer.
  • It is the only component that needs to communicatedirectly with sensor networks.
  • It is responsible for collecting sensing data and translating the raw information into the XML encoding so that other services can use it.
  • The design of SCS provides an interface to both streaming data (built on top of TinyOS) and query based sensor applications (built on top of TinyDB).
  • The following figure illustrates the architecture of the SCS.
sensor planning service
Sensor Planning Service
  • SPS uses a rule engine which reads a set of rules used to decide the feasibility of the plan made by the user.
  • Rules can be in many different languages.
  • The most important component is the scheduler:
    • It first composes the collection request and invokes the SCS to get the observation.
    • Asks the DataCollector to store the observation data for later use by other clients.
    • Sends notification to the WNS indicating the outcome of the collection request.
  • The following figure illustrates the architecture.
web notification service
Web Notification Service
  • The WNS contains two basic components: AccountManager and Notification.
  • The account manager stores data corresponding to users who have registered with the service.
  • The notification component creates and sends messages, using various protocols, to users who have registered.
  • The following figure shows the WNS architecture.
experimental results
Experimental Results
  • The authors present a series of preliminary results.
  • Although the services they implement all work properly, the entire OSWA is not fully implemented.
  • Many implementation issues are left as future work, especially regarding the SCS.
  • This central component needs to be reliable, have good performance, and be scalable.
  • The authors conclude that the SCS will greatly affect the performance and reliability of the entire system.