Propagation of Operation:

Propagation (Also called Triggering) is the automatic application of an operation to a network of objects when the operation is applied to some starting object. Propagation of operations to parts is often a good indicator of propagation. Propagation is very well applicable to aggregated objects, operation carried on whole eventually changes the states of sub objects.

Example: A person owns multiple documents. Each document consists of paragraphs to characters. Copying a paragraph copies all the characters in it. The operation does not propagate in the reverse direction; a paragraph can be copied without copying the whole document. Similarly, copying a document copies the owner link but does not generate a copy of the person which is owner.