LECTURE 6: UML, PRIMITIVE MODELING ELEMENTS

1. UNIFIED MODELING LANGUAGE

2. RELATIONSHIPS

3. GEODATABASE CONCEPTS

4. SIMPLE FEATURE MODEL

A visual language for representing a data model

drawings constructed in Visio
tools to input a drawing to ArcGIS

input data to the data model

1. Model the user's view of data

the "use case"
what are the basic items of information needed to solve the problem?
the data model will need to store everything needed

the MapQuest/cab driver example

2. Define objects and relationships

draw a UML diagram

3. Select the geographic representation

points, lines, areas, rasters, TINs

4. Match to geodatabase elements

specify inheritance relationships

5. Organize geodatabase structure

ESRI data model support site

screen shots

whole model

reference network: edges

reference network: junctions

assets

implementation in ArcGIS

a class is shown as a box

top part contains the name of the class
middle part contains the attributes
lower part contains the methods associated with the class

lines connect boxes and indicate relationships

UNETRANS key

an instance of a class

yet another meaning of the word "object"

in ArcGIS data modeling an object is non-spatial

it is not a point, line, or area
it has no geographic location

its geographic location is not known

it has no shape attribute in its table

an object that has geographic location

a point, line, or area
a TIN or raster

cannot have instances, but can have subclasses

name in italics

Links between classes, shown as lines

Several types of relationships

Association

classes linked by common keys
compare the relational model

multiplicity

1:1

one record in Class A linked to one record in Class B
"is married to"
the class of state capitals linked to the class of states

shown as a solid line

1:n

one record in Class A linked to any number of records in Class B
"owns"
the class of states linked to the class of area codes

shown as a solid line with a * at the B end

or 0...*

if every A is linked to at least one B then use 1...*
a state must have at least one area code

m:n

any number of records in Class A linked to any number of records in Class B
"has visited"
"was ever married to"
the class of mountain lions linked to the class of wilderness areas

shown as a solid line with * at both ends

Class B inherits the properties (attributes, methods) of Class A
white triangle points from B to A

e.g., the class street inherits from the class transportation network link

Class A is the whole, Classes B, C, etc contain the parts
open diamond points to A

e.g., the class airport is an aggregation of the classes runway, hangar, terminal, etc.

if one part of an aggregation is deleted, the whole is not necessarily deleted
if the whole is deleted, the parts are not necessarily deleted

a stronger form of aggregation
closed diamond points to A

the parts and the whole depend on each other

e.g., a polygon and its component arcs and nodes

coverage
MapQuest/cab driver

3. GEODATABASE CONCEPTS

ESRI's new data model

     object-oriented

objects
features
behaviors

     stored in a relational table

          special field for geometric shape
          geometric data incorporated into the database
          no more division between ARC and INFO

Feature dataset

     contains feature classes
     defines topological role of features
     has a coordinate system

Geodatabase

     collection of feature datasets, rasters, TINs
     all data in relational tables
     span contiguous extents
     behavior is coupled with features through rules

Feature geometries

see Zeiler Ch 6 and summary on p114

OGC specification

point

a zero-dimensional feature
coordinates, attributes

multipoint

an unordered collection of points

segment

abstract class

line connecting two points

straight line
arc of a circle
arc of an ellipse
Bezier curve

path

a sequence of connected segments

ring

closed, non-intersecting path
a type of path

polyline

a collection of paths
disjoint or connected

polygon

a collection of rings

can be nested
cannot overlap

envelope

minimum enclosing rectangle (mer)
used to speed up processing

simple feature model

objects with geometry and attributes

point, multipoint

polyline

polygon

annotation
simple junction
complex junction
simple edge
complex edge