uml/class-diagram.md

-**TODO**: Add used OCL defintion and extend example. Clarify usage of operators (`AND`/`OR` instead of `&&`/`||`, `=`/`<>` instead of `==`/`!=`) and explain the possibility of the `if-then-else` pattern.
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 **Sources:** http://www.omg.org/spec/UML/2.5 (Starting at PDF page 192)
 
 # Usage Scenarios