I've never found UML useful for diagraming an entire application. However, I don't know if this is a fault in UML or a problem with the application architecture

I've never found UML useful for diagraming an entire application. However, I don't know if this is a fault in UML or a problem with the application architecture. Applications tend to get large and disjointed. They solve multiple problem sets and consist of several different layers. When we try to take a complex system and put it into a UML diagram things get really hairy fast. UML is more useful when it is used for diagramming the components of systems. This practice also promotes the practice of identifying and decoupling system components. When complex problems or unfamiliar patterns emerge, UML is indispensable. Still the biggest issues I've observed with UML adoption are: 1) A lack of tools developers want to use. 2) As developers become familiar with the codebase (you know, by writing it...) they begin to think it's self explanatory tedious documentation efforts like UML are unnecessary.