Class 2

Question 1

What is UML?

Answer 1

• A standardized, graphical “modeling language” for
  communicating software req/design.
• Allows implementation-independent specification of:
• user/system interactions (required behaviors)
• partitioning of responsibility (OO)
• integration with larger or existing systems
• data flow and dependency
• operation orderings (algorithms)
• concurrent operations
• UML is not “process”!
• it doesn’t tell you how to do things, only what you should do

Question 2

Motivations for UML

Answer 2

• Why do we want UML?
• UML allows us to share high-level design ideas
• UML gives us a standard notation so that we both express
  the same design the same way (….maybe….)
• UML is unambiguous (…for some things…)
• Design is much more apparent from a UML diagram than
  source code
  – design patterns are easy to see in UML
• UML is independent of the implementation language
  – a UML design could be realized in Java, C++, Perl, etc….

Question 3

Types of UML diagrams

Answer 3

There are different types of UML diagram, each with
slightly different syntax rules:
* use cases;
* activity diagrams;
* sequence diagrams;
* class diagrams;
* package diagrams;
* state diagrams;
* deployment diagrams;

Question 4

UML basic syntax

Answer 4

Actors: a UML actor indicates an interface (point of
interaction) with the system.
* We use actors to group and name sets of system
interactions.
* Actors may be people, or other systems.
* An actor is NOT part of the system you are modeling.
An actor is something external that your system has to
deal with.
* Boxes: boxes are used variously throughout UML to
indicate discrete elements, groupings and containment.

Question 5

UML basic syntax

Answer 5

• Arrows: arrows indicate all manner of things,
  depending on which particular type of UML
  diagram they’re in.
• Usually, arrows indicate flow, dependency, association
  or generalization.
• Cardinality: applied to arrows, cardinalities
  show relative numerical relationships between
  elements in a model:
• 1 to 1, 1 to many, etc.
• Constraints: allow notation of arbitrary constraints on
  model elements.
• to constrain the value of a class attribute
• Stereotypes: allow us to extend the semantics of UML
  with English.
• A stereotype is usually a word or short phrase that describes
  what a diagram element does

Question 6

UML basic syntax

Answer 6

• Constraints: allow notation of arbitrary constraints on
  model elements.
• to constrain the value of a class attribute
• Stereotypes: allow us to extend the semantics of UML
  with English.
• A stereotype is usually a word or short phrase that describes
  what a diagram element does

Question 7

UML diagrams: use cases

Answer 7

• A use case encodes a typical user interaction with the
  system. In particular, it:
• captures some user-visible function.
• achieves some concrete goal for the user.
• A complete set of use cases defines the requirements
  for your system:
• everything the user can see and would like to do.
• The granularity of your use cases determines the number
  of them (for your system). A clear design depends on
  showing the right level of detail.
• A use case maps actors to functions. The actors need not
  be people.

Question 8

Activity diagram

Answer 8

A UML activity diagram helps to visualize a use
case at a more detailed level.
It is a behavioral diagram that illustrates the flow
of activities through a system.
UML activity diagrams can also be used to depict a
flow of events in a business process.