D-Bus helps coordinate process lifecycle. It makes it simple and reliable to code a “single instance” (?) application or deamon, and to launch applications and deamons on demand when their services are needed.
D-Bus is designed for two specific use cases:
l A “system bus” for notifications from the system to user sessions, and to allow the system to request input from user sessions
l A “session bus” used to implement desktop environments such as GNOME and KDE
Converting a value from some other representation into the wire format is called marshaling and converting it back from the wire format is unmarshaling.
a block of marshaled values must have a known type signature.
a single complete type is a sequence of type codes that fully describes one type: a single complete type is a basic type code, a variant type code, an array with its element type, or a struct with its fields.
原文：http://www.cnblogs.com/lauraxia/p/3750653.html