Geoinformation Technology: lecture 2 b Object Modeling

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Geoinformation Technology lecture 2 (b)Object
Modeling

• Prof. Dr. Thomas H. Kolbe
• Institute for Geodesy and Geoinformation Science
• Technische Universität Berlin

Credits This material is mostly an english
translation of the course module no. 2
(Geoobjekte und ihre Modellierung) of the open
e-content platform www.geoinformation.net.
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Object-orientation Generalization ?
Specialization

• Abstraction principle for the hierarchical
  structuring of a model
• a specialized class concretises a more general
  class by adding specific properties
• the general class is called superclass, the
  specialized class subclass
• one superclass can have different subclasses
• also one subclass can have different
  superclasses (alsocalled parent classes)

general class
generalization
specialization
specialized class
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OO Example 1 for generalization, specialization
staff_member
research_associate
professor
non_ research_associate

• staff_member is a more general concept as
  non_
  research_associate, research_associate or
  professor
• staff_member is the superclass
• non_ research_associate, research_associate,
  and professor are subclasses

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OO Example 2 for generalization, specialization
geometrical figure
circle
rectangle
triangle

• geometrical figure is a more general concept
  than triangle, circle or rectangle

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Object-orientation Taxonomy

• generalization and specialization describe a
  taxonomical (i.e. systematic) relationship
  between general and specific concepts
• Example Taxonomy of flies with two wings (from
  biology)

Orthorrhapha
Brachycera - flies
Cyclorrhapha
Diptera Flies (with two wings)
Aschiza
Schizophora
Nematocera - mosquito
Acalyptratae
Calyptratae
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Object-orientation Aggregation vs.
Generalization

• What is the difference between an aggregation and
  a generalization?
• aggregation and generalization build hierarchies,
  but
• aggregation relates objects
• generalization relates classes
• Please note the systematic difference between
  following relationships
• University Faculty (aggregation of objects)
• Rectangle Figure (generalization of the same
  object)

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Object-orientation Inheritance and
specialization (I)

• A superclass represents a concept.
• A subclass specializes this concept, such that
  that it
• explicitly adopts the attributes of the
  superclass
• Inheritance of properties
• explicitly adopts or overrides methods of the
  superclass
• Inheritance of the behavior
• defines new attributes
• defines new methods

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Object-orientation Example 1 for Inheritance
student
staff member

• name
• first name
• registration number
• - subject
• address
• date of birth
• registration-date
• Bachelor
• Master

• name
• first name
• personnel number
• - institute
• address
• date of birth
• bank account no.
• salary

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Object-orientation Example 1 for Inheritance
person

• name
• first name
• - address
• - date of birth

student
staff member

• - registration number
• - subject
• registration-date
• . . .

• personnel number
• - bank account no.
• salary
• . . .

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Object-orientation Example 2 Overriding
geometrical figure

• center Point
• visible Boolean

display ( ) delete ( ) move ( )
circle
rectangle
triangle

• radius number

• a number
• b number
• c number

• a number
• b number

display ( ) delete ( )
display ( ) delete ( )
display ( ) delete ( )
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Object-orientation Inheritance and
specialization (II)

• subclasses differ systematically wrt. each other
• attributes and methods of a class represent a
  self-contained concept
• the specialized class is fully compatible to the
  general class
• attributes and methods of the superclass do not
  have to be repeated in the specification of the
  subclass(es)

geometrical figure

• center Point
• visible Boolean

display( ) delete( ) move( )
circle
rectangle
triangle

• radius number

• a number
• b number
• c number

• a number
• b number

display( ) delete( )
display ( ) delete ( )
display ( ) delete ( )
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Object-orientation Polymorphism

• congeneric (similar) methods, that are to be
  executed on objects of different classes, can be
  named with the same identifier
• when calling such a method, the (most)
  object-specific one is activated in each case
• advantage of the polymorphism specific objects
  can be handled in a general way
• triangles, circles, and rectangles can be treated
  as geometrical figures

geometrical figure

• center Point
• visible Boolean

display ( ) delete ( ) move ( )
circle
rectangle
triangle

• radius number

• a number
• b number
• c number

• a number
• b number

display ( ) delete ( )
display ( ) delete ( )
display( ) delete( )
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Example 2 with spatial reference
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Example 2 state - district - municipality -
parcel
state
district

1..

• name string
• inhabitants number
• area number

• name string
• inhabitants number
• area number

getname( ) name getinhabitants(
)number getarea( ) number
getname( ) string getinhabitants(
)number getarea( ) number
Declare the methods
Name the relationships
Declare the multiplicities
Declare the attributes
municipality
property

• name string
• inhabitants number
• area number

• owner Person
• area number

1..
1..


getname( ) string getinhabitants(
)number getarea( ) number
getowner( ) Person getarea( ) number
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Example 2 property - parcel - polygon

• Can this subdivision of space can be extended
  further than "property"?
• at first
• transition from the legal object "property" to
  the geometrical object "polygon"

1 . . n
property
parcel
polygon
geometry
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Example 2 Topological relationships of
polygons
bounds
node
edge
bounds
face
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Example 2 polygon edge node - point
1..2
3 . .
polygon
edge
? bounds
2 . .
Declare the multiplicitys and names
Name the relationships
? bounds
2
1
1
geometry
point
node
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Example 2 Class point
point

• latitude degree
• longitude degree
• X number
• Y number
• projection text
• registration textGPS
• registration-date date

getlatitude( ) degree getlongitude( )
degree setlatitude(lat degree)
setlongitude(lon degree) getX( ) number
getY( ) number . . .
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Data Modelling Literature

• Balzert, Heide Lehrbuch der Objektmodellierung.
  Akademischer Verlag, 1999
• Oestereich, Bernd Objektorientierte
  Softwareentwicklung Analyse und Design mit
  der Unified Modeling Language. 4. Auflage -
  Oldenbourg,
• München Wien, 1998
• (english titles will be added soon)