UML and Use Cases

This is a very broad question. And requires good deal of discussion. What basically you want to know is -- What is UML and how to use it and why. As I said, this is a huge subject. I will try to explain in brief.

--------------------------------------------------------------------------------------------------------------------
The Unified Modeling Language™ - UML - is the way the world models application structure/behavior/architecture, business process, and data structure.  

UML, along with the Meta Object Facility provides a key foundation for OMG's Model-Driven Architecture®, which unifies every step of development and integration from business modeling, through architectural and application modeling.
--------------------------------------------------------------------------------------------------------------------

Above text is simplified version of what the masters themeselves say about UML. In layman's terms, UML is a modelling tool to aid software architects and application developers in all phases of SDLC.


A use case is one of the many tools described in teh UML specification. Let us see what the masters say about the Use Cases.


--------------------------------------------------------------------------------------------------------------------
A use case is a behaviored classifier that defines a sequence of actions, performed by one or more actors and the system, that results in an observable result of value to one or more actors.

A use case always has one main flow of events (also known as a basic course of action, and will generally have at least one exceptional flow of events (or alternate course of action).
--------------------------------------------------------------------------------------------------------------------

In simpler words, a use case defines a sequence of actions, performed by one or more actors and the system that results in an observable result of value to one or more actors. A use case has a flow of events (and will generally have at least one exceptional flow of events.

In even simpler words, a use case is a sequence of actions that are tobe performed by human users of a system or the system itself. Such sequence of actions generally have only one flow of events. But they may have an exceptional flow of events as well (exception handling).

You may find a lot of leads from these pages:


http://www.uml.org/
http://www.omg.org/technology/documents/formal/uml.htm
http://www.softdocwiz.com/Dictionary.htm

Thanks for all that info.

Can you say why I should use it?  Why do I need to learn it?  Why can't I just go about it the natural way...
I.e.  Verbal and written specs. , flow charts, and screen mock ups?

What do these tools do that can't be done with my current strategy?