How to Understand and Describe UML Class Diagrams?

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Discussion Overview

The discussion centers around understanding and describing UML class diagrams, specifically two diagrams presented by a participant. The focus includes interpreting class relationships, dependencies, and the notation used in UML diagrams.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses difficulty in reading and explaining the first UML class diagram, noting subclasses of "bird" such as "Flycatcher" and "Cardinal," while being uncertain about other classes.
  • Another participant attempts to clarify the unclear terms next to "bird," suggesting they might be "Tree" and "Seed," and questions the meaning of the dashed arrow in the diagram.
  • There is a discussion about the meaning of the dashed line and solid line, with one participant proposing that the dashed line indicates a "co-requisite" and the solid line indicates a "pre-requisite," while another challenges this interpretation, suggesting it indicates "dependency."
  • A suggestion is made for the original poster to seek out documentation or resources on UML to better understand the symbols and notation used in the diagrams.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the meanings of the lines in the UML diagrams, with differing interpretations of the dashed and solid lines. There is also uncertainty regarding the specific classes represented in the diagrams.

Contextual Notes

Participants mention the importance of having reference materials for UML, indicating that understanding may depend on access to such resources. The discussion reflects varying levels of familiarity with UML notation.

Who May Find This Useful

Individuals learning UML, those interested in software design and architecture, and participants seeking clarification on class diagram notation may find this discussion relevant.

XodoX
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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.
 
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XodoX said:
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?

XodoX said:
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?
 
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.
 
XodoX said:
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.
 

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