How to Understand and Describe UML Class Diagrams?

[XodoX]

I'm having difficulties with two UML class diagrams.

That's the first one:

http://img821.imageshack.us/i/umlv.png/

I can't really read the words next to bird, but it looks like "Tran" and "Saad" ( some kind of bird?) I don't really know how to explain this? You're supposed to describe it. Flycatcher and Cardinal are subclasses of bird, and the two others are, I don't know, some other class of birds?

Then, there's this diagram:

http://img193.imageshack.us/i/uml1.png/

How do I describe what this diagram illustrates? The first box says "aSim:Sim" The other one "simList:Object". I don't get it.

 

[Grep]

I can't really read the words next to bird, but it looks like "Tran" and "Saad" ( some kind of bird?) I don't really know how to explain this? You're supposed to describe it. Flycatcher and Cardinal are subclasses of bird, and the two others are, I don't know, some other class of birds?

Wow that's hard to read. Best I can make it out, and using a bit of logic, it's "Tree" and "Seed". You remember what the dashed arrow means?

How do I describe what this diagram illustrates? The first box says "aSim:Sim" The other one "simList:Object". I don't get it.

Do you not have a reference for sequence diagrams? aSim:Sim is in the form name:ClassName. Note the sequence of events. What message starts it off, and what happens as a result?

 

[XodoX]

ops, lol, yeah, tree and seed. That's all I have. Nothing else. I think the dashed line means something like "co-requisite", and the other line "pre-requisite". Like, you know, in terms of hierarchy - the dependency.

 

[Grep]

ops, lol, yeah, tree and seed. That's all I have. Nothing else. I think the dashed line means something like "co-requisite", and the other line "pre-requisite". Like, you know, in terms of hierarchy - the dependency.

Don't think the "co-" and "pre-" thing is true, but the dashed line should indeed mean "dependency". So a Bird class depends on the Tree and Seed classes.

If you don't have any documentation for UML, I strongly suggest you find one. There's some good books published for it, and of course there's a lot of information on the web.

For example, this site seems to have a useful "UML Reference Card":

http://www.holub.com/goodies/uml/

A little googling should get you the info you need to understand the symbols (and more). Of all skills that get you far when learning things, research skills are some of the most useful.