●  It  should  go  without  saying  that  the  focus  of  UML  is  modeling.  However,  what  that means, exactly, can be an open-ended question.  （71）  is a means to capture ideas, relationships,decisions,  and  requirements  in  a  well-defined  notation  that  can  be  applied  to  many  different domains.  Modeling  not  only  means  different  things  to  different  people,  but  also  it  can  use different pieces  of UML depending on what you are trying to  convey. In general, a UML model is  made  up  of  one  or  more  （72）  .  A  diagram  graphically  represents  things,  and  the relationships between these things. These  （73）  can be representations of real-world objects,pure software constructs, or a description of the behavior of some other objects. It is common for an  individual  thing  to  show  up  on  multiple  diagrams;  each  diagram  represents  a  particular interest,  or  view,  of  the  thing  being  modeled.  UML  2.0  divides  diagrams  into  two  categories:structural  diagrams  and  behavioral  diagrams.  （74）  are  used  to  capture  the  physical organization of the things in your system, i.e., how one object relates to another.  （75）  focus on  the  behavior  of  elements  in  a  system.  For  example,  you  can  use  behavioral  diagrams  to capture requirements, operations, and internal state changes for elements.