Java Programming

Hi all,

Just looking up these two terms and I'm not really sure on what they each mean. I found the following explanation via google:

"Aggregation implies that one object owns or is responsible for another object. Generally we speak of an object having or being part of another object. Aggregation implies that an aggregate object and its owner have identical lifetimes."

"Acquaintance implies that an object merely knows of another object. Sometimes acquaintance is called "association" or the "using" relationship. Acquainted objects may request operations of each other, but they aren't responsible for each other."

I think I get the aggregation explaination but I'm not very clear on the aquaintance one.

If aggregation is, say, a person object having a head object as part of it, what is a real world example of the acquaintance relationship?

Thanks,

Illu