- Presence is used on networks to indicate the status of available parties and their location.
- Presence provides identity, status and location.
- The service that manages presence is called the presence service.
- Many presence services rely on agents called watchers, which are small programs that relay a client’s ability to connect.
- Presence information is used in cloud computing services like VoIP, instant messaging services(IM) and GPS.
- Presence is playing an important role in cell phones.
- Eg: AroundMe on the Apple iPhone.
- The presence service is provided by the GPS locator inside the phone, which provides a location through AT&T (the service provider) to the application.
- Presence is an essential and growing component of cloud-based services.
- Microsoft’s Windows Identity Foundation is a claims-based presence system.
- A standard called the Extensible Messaging and Presence Protocol (XMPP) can be used with a federation system called the Jabber XCP to provide presence information.
- Jabber XCP is popular because it is an extensible development platform which is platform-independent and supports several communications protocols.
- In SOA protocols such as SOAP/REST/HTTP support unidirectional data exchange. You request a service/data, and a response is supplied.
- SOA architectures don’t scale well and can’t supply high-speed data transfers required by the services that are based on presence service technologies.
- SOA also has the problem of services that have trouble penetrating firewalls.
- Jabber and XMPP were created to solve these barriers
