Object Oriented Implementation

OBJECT-ORIENTED
SOFTWAREENGINEERING
UNIT 06 : Object Oriented Implementation
© 2018 , PRAMOD PARAJ
UL
I

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These slides are part of teaching materials for Object Oriented
Software Engineering (OOSE). These slides do not cover all
aspect of learning OOSE, nor are these be taken as primary
source of information. As the core textbooks and reference
books for learning the subject has already been specified and
provided to the students, students are encouraged to learn
from the original sources.
Contents in these slides are copyrighted to the instructor and
authors of original texts where applicable.
OOSE UNIT 06 - Object Oriented Implementation

Reference:
Bruegge B., and Dutoit A. H. 2010, Object-oriented Software
Engineering using UML, Patterns and Java, 3rd ed., Prentice Hall
(Chapter 10)

MAPPINGCONCEPTS
 Model transformations
 Refactorings
 Forward engineering
 Reverse engineering

MODELTRANSFORMATION
Applied to object model and results in another object
model.

REFACTORING
To improve source code readability or modifiability
without changing its behavior.

FORWARDENGINEERING

REVERSEENGINEERING
 Mapping source code elements back to a set of
model elements.
 CASE tools help build an approximate model.
 Approximate – because forward engineering may lose
information e.g. associations are turned into collections
of references.

TRANSFORMATIONPRINCIPLES
 Each transformation must address a single criteria.
 Each transformation must be local.
 Each transformation must be applied in isolation to
other changes.
 Each transformation must be followed by a
validation step.

TRANSFORMATIONS
Transform models
 Optimising the object design models i.e. class models
 Mapping associations to collections
 Mapping operations contracts to exceptions
 Mapping the class model to a persistent storage schema

OPTIMISINGTHEOBJECTDESIGNMODEL
Optimising access paths
 Repeated association traversals – frequent operations
between two objects through other objects must be simplified
by creating an association.
 “Many” associations – decrease search time by reducing the
“many” to “one”
 Misplaced attributes – reduce excessive modeling, calling
vs. hosting classes

Collapsing objects

Delaying
expensive
computations

Caching the result of expensive computations
 If some values are repeatedly access after
computation, its better to keep them in cache.

MAPPINGASSOCIATIONSTOCOLLECTIONS

QUALIFIEDASSOCIATIONS

ASSOCIATIONCLASSES

MAPPINGCONTRACTSTOEXCEPTIONS
Contracts help in;
 Checking preconditions
 Checking postconditions
 Checking invariants
 Dealing with inheritance

Example

MAPPINGOBJECTMODELSTOPERSISTENTSTORAGESCHEMA
Mapping classes and attributes

Mapping associations

Mapping inheritance
relationships
(vertical)

Mapping inheritance
relationships
(horizontal)

MANAGINGIMPLEMENTATION
Documenting transformations
 For given transformation, use
same tool
 Keep the contracts in the source
code, not in the object design
model
 Use the same names for the
same objects
 Make transformations explicit
Assigning responsibilities
 The core architect
 The architecture liaison
 The developer

❃ Read ‘10.6 ARENA Case Study’ from
Bruegge B., and Dutoit A. H. 2010, Object-oriented Software Engineering using
UML, Patterns and Java, 3rd ed., Prentice Hall (Chapter 10)

End of Unit 06 : Object-oriented Implementation

Object Oriented Implementation

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