Information Technology Reference
Making a ubiquitous system means to provide devices capable of obtaining
information from the environment in which they are incorporated and meet
the demands of their clients.
Clients are moving in a random manner into the environment, using devices
such as PDAs, to 'discover' the services that the environment offers. But what
exactly is meant by 'service'? A service is an entity that can be used by a person,
a program or even by another service. A service can be computational capability,
memory, a communication channel, a hardware device or another user .
In a nutshell, if we want to indicate two possible types of services, we
may say, print a document and convert a document from one format to
another. To enable future communication between different entities, it is
essential that each one of them is aware of what is available in the vicinity,
that is, capable of identifying other entities in the vicinity and interact with
one of them using any of the services it offers.
The resolution of this problem is called 'service discovery'. All this must
be done taking into account the interests of the client, which may be: finding
the closest device with shorter queues and in a manner entirely independent
of the device's position .
However, allowing a user to take advantage of the services provided by
the environment is not an easy problem to solve: we must take into account
issues such as the position of the user (which may vary) or of other objects
and knowledge of place . We will discuss these issues in the next few
paragraphs, gradually putting together the 'pieces' to create a system oriented
to the discovery of a service.