Objects and lifelines

[zyx]

Again I apologize for my bad english.

What is the difference between objects and lifelines? A lifeline is an object that participates of a specific interaction?

[Geert Bellekens]

A lifeline is an object that participates of a specific interaction?

Sort of. A lifeline lives withing the interaction, and represent a "ConnectableElement". This  connectable element is an instance of a classifier (-> object) that can be linked with a connector.

From UML superstructure 2.3

ConnectableElement
A ConnectableElement is an abstract metaclass representing a set of instances that play roles of a classifier. Connectable
elements may be joined by attached connectors and specify configurations of linked instances to be created within an
instance of the containing classifier.

Geert

[sargasso]

... and if that quote doesn't clear everything up I will donate my entire fortune (about 11c) to the nearest church of the Utterly Meaningless Linguistics.
 

OK, I've been staring at this for 1.5 hours now (nothing on TV). So far I've got through the first sentence.

A "lifeline" is an object, being an instance of a "connectable element".
Which is a classifier, albeit abstract and meta.
But that still makes it an object.

Now, apparently a "connectable element" is also  an "abstract metaclass representing a set of instances that play roles of a classifier", which having deciphered over 10^¹⁹ iterations seems to say that it is actually a classifier of objects representing classifiers, or to be banal "a class of objects that are instances of classes" ... ... ...

Common sense and many programming languages tend to define  "a class of objects that are instances of classes" as an "Object".  So, so far, in reply to the OP I would say yes, they are objects.  But I haven't got as far as the second sentence yet.

Please note that I am being serious here. This is not a "b" post.

p.s. Oftimes your humble correspondent has been accused and yetsofar is innocent in intent of any and all instances of mentioning the ult.  A wise and erudite pundit once expounded that one should "eschew obfuscation" in any commercial, official or personal communications lest one's intent benign or otherwise be misconstrued. On my personal behalf I opine that perchance it would prove beneficial should OMG adopt said precept in any instance.