Underwater sound has probably been used by marine specimens for millions of years as a communication capability among the members of a same species. It is said that in 1490, Leonardo Da Vinci wrote the following sentence: “If you cause your ship to stop and place the head of a long tube in the water and place the outer extremity to your ear, you will hear ships at a great distance from you” (Urick, 1983); being perhaps the first recorded experiments about hearing underwater sounds. In 1826 on Lake Geneva, Switzerland, the physicist Jean-Daniel Colladon, and his mathematician friend Charles-Francois Sturm, made the first recorded attempt to determine the speed of sound in water. In their experiment, the underwater bell was struck simultaneously with ignition of gunpowder on the first boat. The sound of the bell and flash from the gunpowder were observed 10-miles away on the second boat. The time between the gunpowder flash and the sound reaching the second boat was used to calculate the speed of sound in water. Colladon and Sturm were able to determine the speed of sound in water fairly accurately with this method. (Colladon, 1893).
In this section, we provide background information about ontology and user profiles which can be used to address some of the challenges involved in Web services discovery.
A Web service is an interface that describes a collection of operations that are network accessible through standardized XML messaging specifications such as SOAP, WSDL and UDDI. It provides open XML-based mechanisms for application interoperability, service description, and service discovery (Kim & Jain, 2005). A large number of Web services are already available on the internet, making Web services discovery a major task in service-oriented business application development. A widely used approach for discovering Web services is based on UDDI (Bin, Yan, Po, & Juanzi, 2005). UDDI uses a keyword based discovery feature which may not provide satisfactory query results because it does not take into account the context of the query. Recent research has proposed the use of ontology based query to improve the accuracy and relevance of search results (Bin et al., 2005; Maximilien & Singh, 2004; Zhou et al., 2005).
Key Terms in this Chapter
Proactive and Reactive Routing Protocols: Represent two different styles of routing packets. The former ones maintain updated the routing info by periodically distributing routing info throughout the network. In contrast, a reactive routing protocol finds a route on demand by flooding the network with route request packets.
SONAR (sound navigation and ranging): A device that uses the properties of underwater sound propagation to communicate, navigate, or detect other vessels. It sends pulses of sound to probe the sea, and the echoes are then processed to extract information (shape, distance, composition, etc.) about the sea, its boundaries, and submerged objects.
Frequency Hopping Spread Spectrum (FHSS): A modulation technique that can be described as a frequency modulation that is repeatedly changing the frequency of the carrier signal in the full available spectrum for transmission.
Direct Sequence Spread Spectrum (DSSS): A modulation technique where the data signal is multiplied by a pseudorandom binary sequence at a frequency much higher than that of the original signal, thereby spreading the energy of the original signal into a much wider band.
WSNs (wireless sensor network): Can be defined as a particular case of MANETs in the sense that each node is required to record and wirelessly distribute environmental data obtained through a set of sensors attached to it. They are typically small and low-power consuming devices, and use to be deployed in high node density networks.
AUVs (autonomous underwater vehicles): Those underwater vehicles able to navigate autonomously to collect sensor data in a specific control area. The most common use of these vehicles is related with the oil and gas industry, allowing one to obtain maps of the seafloor before starting to build the subsea infrastructure.
Hydrophone: A microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates electricity when subject to a pressure change.
MANETs (mobile ad hoc networks): Refer to those wireless networks composed of mobile nodes that can communicate between them without the need of any kind of infrastructure (base stations).
Point Coordination Function (PCF): A MAC protocol, used in wireless local area networks (WLANS), that relays a central coordinator, usually known as an access point (AP). The access to the medium is governed by APs unit allowing an ordered and collision-free access to the network.