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An interface is a collection of
operation signatures and/or attribute definitions that
ideally defines a cohesive set of behaviors. Interfaces
are implemented, “realized” in UML parlance, by classes
and components – to realize an interface, a class or
component must implement the operations and attributes
defined by the interface. Any given class or component
may implement zero or more interfaces, and one or more
classes or components can implement the same interface. |
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Figure 1. The
internals of the seminar component.
 Figure 2.
Class implementing interfaces.
Figure 3.
Logical component architecture.
- Depict One Interface Per Port.
Ports are connection
points between a classifier and its environment that
are depicted on the side of frames as small rectangles.
In
Figure 1 each port has exactly
one interface, which is logically cohesive and thus does
not reveal anything about the internal design of the Seminar component.
- Depict One Port Per
Realizing Class. Another approach to organizing the
interfaces for SeminarComponent of
Figure 1 would be to have a single port
offering the Enrollment, Transcript, and
DataEntity interfaces. This would make for a
more compact diagram although contradicts
Depict One Interface Per
Port: choose an approach and stick to it.
- Provided
Interfaces on the Left. In
Figure 1 the provided
interfaces are depicted using “lollipop” notation.
- Required
Interfaces on the Right. Required interfaces, such as
Student, Persistence, and XMLProcessor in
Figure 1 are depicted in
UML 2 as “sockets”.
- Apply Realizes Relationships for Ports. In
Figure 1 SeminarComponent realizes the three ports on the
left of the frame and the Enrollment class
delegates to the Student port.
-
Reflect Implementation Language Constraints in Interface
Definitions. In Figure 2,
the interface includes a public
attribute named POID and several public
operations. Unfortunately, it could not be implemented
in Java because this language does not (yet) support
instance attributes in the definition of interfaces.
- Name
Interfaces According to Language Naming Conventions.
- Prefer
“Lollipop” Notation to Indicate Realization of an
Interface. As you can see in
Figure 2 there are two ways to
indicate that a class or component implements an
interface: the lollipop notation used with the Serializable interface and the realization line (the
dashed line with a closed arrowhead) used with the PersistentObject interface.
- Define
Interfaces Separately from Your Classifiers.
- Do
Not Depict the Operations and Attributes of
Interfaces in Your Classes.
- One
Label Per Interface Connection. In
Figure 3
you see that the IPersistence interface is
indicated twice, once for the lollipop and once for the
socket.
- Place Interface Labels Above The Interface.
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The Elements of UML 2.0 Style describes a collection
of standards, conventions, and
guidelines
for creating effective
UML diagrams. They are based on sound, proven
software engineering principles that lead to diagrams
that are easier to understand and work with. These
conventions exist as a collection of simple, concise
guidelines that if applied consistently, represent an
important first step in increasing your productivity as
a modeler. This book is oriented towards
intermediate to advanced UML modelers, although there
are numerous examples throughout the book it would not
be a good way to learn the UML (instead, consider
The Object Primer). The book is a brief 188
pages long and is conveniently pocket-sized so it's easy
to carry around. |
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The Object Primer 3rd Edition: Agile Model Driven
Development with UML 2 is an
important reference book for agile modelers,
describing how to develop 35
types of agile
models including all 13
UML 2 diagrams.
Furthermore, this book describes the techniques
of the
Full Lifecycle Object Oriented Testing
(FLOOT) methodology to give you the fundamental
testing skills which you require to succeed at
agile software development. The book also
shows how to move from your agile models to
source code (Java examples are provided) as well
as how to succeed at implementation techniques
such as
refactoring and
test-driven development
(TDD). The Object Primer also includes a
chapter overviewing the critical database
development techniques (database refactoring,
object/relational mapping,
legacy analysis, and
database access coding) from my award-winning
Agile Database Techniques
book. |
 |
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Agile Modeling: Effective Practices for Extreme
Programming and the Unified Process is the seminal
book describing how agile software developers approach
modeling and
documentation. It describes principles and
practices which you can tailor into your existing
software process, such as
XP, the
Rational Unified Process (RUP), or the
Agile Unified Process (AUP), to streamline your
modeling and documentation efforts. Modeling and
documentation are important aspects of any software
project, including agile projects, and this book
describes in detail how to
elicit requirements,
architect, and then
design your system in an agile manner. |
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I actively work with clients around the world to
improve their information technology (IT) practices as
both a mentor/coach and trainer. A full description of
what I do, and how to contact me, can be
found here.
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