Department of Geoinformation Science Technische Universitt Berlin WS 2006/07 Geoinformation...

Department of Geoinformation Science

Technische Universität Berlin

WS 2006/07

Geoinformation Technology: lecture 2 (b)

Object Modeling

Prof. Dr. Thomas H. Kolbe

Institute for Geodesy and Geoinformation ScienceTechnische 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.

http://www.geoinformation.net/

WS 2006/072 T. H. Kolbe – Geoinformation Technology: lecture 2


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

specialized class

generalization specialization



OO: Example #1 for generalization, specialization

„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

staff_member

research_associate professornon_ research_associate



OO: Example #2 for generalization, specialization

geometrical figure

circle rectangle triangle

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



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)

Diptera – Flies (with two wings)

Brachycera - flies

Nematocera - mosquito

Orthorrhapha

Cyclorrhapha

Aschiza

Schizophora

Acalyptratae

Calyptratae



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)



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



Object-orientation: Example #1 for Inheritance

student- name

- first name

- registration number

- subject

- address

- date of birth

- registration-date

- Bachelor

- Master

staff member- name

- first name

- personnel number

- institute

- address

- date of birth

- bank account no.

- salary



Object-orientation: Example #1 for Inheritance

student- registration number

- subject

- registration-date

- . . .

staff member- personnel number

- bank account no.

- salary

- . . .

person- name- first name- address- date of birth



Object-orientation: Example #2: Overriding

geometrical figure


-center: Point -visible: Boolean

+display ( )+delete ( )+move ( )

-a: number-b: number-c: number

+display ( )+delete ( )

-a: number-b: number


-radius: number




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



+display( )+delete( )+move( )





-radius : number

+display( )+delete( )



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



+display ( )+delete ( )+move ( )


+display( )+delete( )



-radius : number




Example #2 with spatial reference



Example #2: state - district - municipality - parcel

state district

municipalityproperty

1..* -name: string -inhabitants: number -area: number

+getname( ): name+getinhabitants( ):number+getarea( ): number

-name: string -inhabitants: number -area: number

+getname( ): string+getinhabitants( ):number+getarea( ): number

-owner: Person -area: number

+getowner( ): Person+getarea( ): number

-name: string -inhabitants: number -area: number

+getname( ): string+getinhabitants( ):number+getarea( ): number

Declare the attributes Declare the methods Name the relationships

Declare the multiplicities

1..* 1..*



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"

property parcel polygon1 . . n

geometry



Example #2: Topological relationships of polygons

face

nodeedge

bounds

bounds



Example #2: polygon – edge – node - point

polygon edge

point node

1..2 3 . . *

2 . . *

1 12

bounds

bounds

geometry

Declare the multiplicitys and names Name the relationships



Example #2: Class ‘point‘

point- latitude: degree - longitude: degree - X: number- Y: number- projection: text - registration: text=“GPS“ - registration-date: date

+ getlatitude( ) : degree + getlongitude( ) : degree + setlatitude(lat: degree) + setlongitude(lon: degree) + getX( ) : number+ getY( ) : number+ . . .



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)

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