Geographical Data Modeling UML and Data Modeling Elements Examples from the Marine Data Model and ArcHydro (Thanks to Dawn Wright)

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Geographical Data Modeling UML and Data
Modeling ElementsExamples from the Marine Data
Model and ArcHydro (Thanks to Dawn Wright)

• Longley et al., ch. 8

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Models for GIS

• representation of reality --gt model
• GIS itself is based on a model of complexity and
  used to model complexity
• Not a full representation of reality even at 11

• data model limited representation of reality
• a discretization or partitioning of space
• finite, discrete nature of computing devices

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Data Model

• Representation of information about a form or a
  process
• E.g. a weather map with isotherms
• FIELD grid
• OBJECT isoline
• A good model allows us to infer process
• FIELD or OBJECT geo-relational

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3 Data Models

• geo-relational coverage (object view from
  classic ArcInfo polys)
• geo-relational shapefile (object view from
  ArcView)
• geodatabase (object-oriented new in ArcGIS 8,9
  etc.)

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Object Oriented GIS (p. 191)

• Object a self-contained package of information
  describing an entity
• Collection of objects class
• Objects can have behavior encapsulation
• Inheritance reusable objects
• Polymorphism-objects can have their own
  implementation for application-e.g. create, draw,
  delete

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Georelational Data ModelClassic ArcInfo and
ArcView
Arc
Info
command line interface Unix, NT, Windows ArcView
as interface
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ArcInfo Coverage as a Data Structure
Image courtesy of Louisville/Jefferson County
Information Consortium, Kentucky
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Data Structure

• Not tied to process at all
• Concerned simply with what can be computed and
  what cant
• Way in which the data model is represented in the
  GIS
• DEM for grid or layer model (e.g. array)
• contour for isoline model
• TIN for Delaunay triangulation model
• coverages, shapefiles for geo-relational
• geodatabase for OO geodatabase

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ArcGIS 9 Icons
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Geodatabase

• Features and attributes as objects
• Relationships among features encoded
• Validation or editing rules, behaviors
• Container for
• Vector, raster, tabular data
• Relationships
• Topology

MS-Office
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Relationships for a feature
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ArcGIS Data Modelssupport.esri.com/datamodels.cfm
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ArcMarine dusk.geo.orst.edu/djl/arcgis
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Data Modeling for Spatial Analysis

• What is spatial analysis?
• "a set of methods whose results change when the
  locations of the objects being analyzed change"
• Methods for working with spatial data
• to detect patterns, anomalies
• to find answers to questions
• to test or confirm theories
• deductive reasoning-general to specific
• to generate new theories and generalizations
• inductive reasoning-specific to general

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What is Spatial Analysis (cont.)

• Methods for adding value to data
• in doing scientific research
• in trying to convince others
• A collaboration between human and machine
• How do we set up the framework for spatial
  analysis?
• Data model to data structure

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A Georelational to a Geodatabase Model

• Coverage and shapefile data structures
• homogenous collections of points, lines, and
  polygons with generic, 1- and 2-dimensional
  "behavior" as operations
• Cant distinguish behaviors
• Point for a marker buoy, same as point for
  observation
• smart features in a geodatabase
• lighthouse must be on land, marine mammal siting
  must be in ocean
• Objects can self-police

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Purpose of ArcHydro, ArcMarine etc.

• Basic template for implementing GIS projects
• input, formatting, geoprocessing, creating maps,
  performing analyses
• Basic framework for writing program code and
  maintaining applications
• development of tools for the community
• Promote networking and data sharing through
  established standards
• common modelinteroperability

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ArcMarine Design Strategy
Generic Marine Data Model
Inheritance
User Group Data Model
User Group Data Model
User Group Data Model
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Geodatabase Concepts

• ESRI's data object-oriented data model
• objects, features, behaviors
• Geodatabase
• collection of feature data sets, rasters, TINs
• all data in relational tables
• behavior is coupled with features through rules
  (object-orientation)
• Supports model-builder for processes
• Feature data set
• contains feature classes
• defines topological role of features
• has a coordinate system

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Geodatabase Concepts ( cont. )

• Feature class
• stored in a relational table
• special field for geometric shape
• geometric data incorporated into the database
• Point, multipoint, segment, path, ring, polyline,
  polygon

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Geodatabase Feature Class Geometries
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Modeling Process
Conceptual Model Lists, flow diagrams, etc
Real World Objects and relationships
Logical Model Diagram in CASE Tool
Physical Model
Database Schema (Object state)
Graphic courtesy of ESRI
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Data Model Levels
Reality
Human-oriented
Conceptual Model
Increasing Abstraction
Logical Model
Computer-oriented
Physical Model
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Specific Steps in Data Modeling

• (1) Conceptualize the user's view of data
• what are the basic features needed to solve the
  problem?
• (2) Select the geographic representation
• points, lines, areas, rasters, TINs
• (3) Define objects, features, and relationships
• draw a UML diagram, specify relationships,
  behaviors
• (4) Match to geodatabase elements
• Refine relationships, behaviors
• (5) Organize geodatabase structure, add data

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( 1 ) Users View of Data
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( 1 ) Users View of Data cont.
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(2)Select geographic rep.
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Steps in Data Modeling

• (1) Conceptualize the user's view of data
• what are the basic features needed to solve the
  problem?
• (2) Select the geographic representation
• points, lines, areas, rasters, TINs
• (3) Define objects and relationships
• draw a UML diagram, specify relationships,
  behaviors
• (4) Match to geodatabase elements
• Refine relationships, behaviors
• (5) Organize geodatabase structure, add data

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Unified Modeling Language

• Entity-relationship diagrams

• Design the methodologies, diagram notations
• UML
• Not a design methodology
• Just a diagrammatic notation based on methods
• Endorsed by leading software and database
  companies

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UML ( cont. )

• Diagrammatic notation visual language...
• For constructing a data model
• Drawings, relationships constructed in Visio
  (other tools available)
• Tools to input a drawing into ArcGIS
• input drawing to the data model

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UML Notation

• a class is shown as a box
• top part contains the name of the class
• lower part contains the attributes
• methods associated with the class
• lines connect boxes and indicate relationships

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Graphic courtesy of Maidment et al., ArcHydro
team
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UML Notation ( cont. )

• Abstract class
• specify subclasses underneath
• Mammals w/human or dog feature classes
• no new instances
• Feature Class
• Specify subtypes underneath
• Human, dog, cat

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Objects and Features

• Object (real world)
• in ArcGIS an object is non-spatial
• it is NOT a point, line, or area
• it has no geographic location
• it has no shape attribute in its table
• Drainage network, ship, vehicle, customer,
  lake, house, etc.
• Feature (spatial context)
• an object that has geographic location
• a point, line, area, TIN, raster

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Relationships

• Links between classes, shown as lines
• One to one
• One to many
• Many to many

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Relationships (cont.)

• 11 - solid line
• 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
• 1n - solid line with at one end
• 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

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Relationships (cont.)

• mn - solid line with at both ends
• any number of records in Class A linked to any
  number of records in Class B
• "has visited
• "was never married to"
• the class of mountain lions linked to the class
  of wilderness areas

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Graphic courtesy of Maidment et al., ArcHydro
team
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Type Inheritance

• White triangle
• Class B inherits the properties (attributes,
  methods) of Class A
• the class street inherits from the class
  transportation network
• Solid diamond
• the parts and the whole depend on each other

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Graphic courtesy of Maidment et al., ArcHydro
team
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Steps in Data Modeling

• (1) Conceptualize the user's view of data
• what are the basic features needed to solve the
  problem?
• (2) Select the geographic representation
• points, lines, areas, rasters, TINs
• (3) Define objects and relationships
• draw a UML diagram, specify relationships,
  behaviors
• (4) Match to geodatabase elements
• Refine relationships, behaviors
• (5) Organize geodatabase structure, add data

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Steps in Data Modeling

• (1) Conceptualize the user's view of data
• what are the basic features needed to solve the
  problem?
• (2) Select the geographic representation
• points, lines, areas, rasters, TINs
• (3) Define objects and relationships
• draw a UML diagram, specify relationships,
  behaviors
• (4) Match to geodatabase elements
• Refine relationships, behaviors
• (5) Organize geodatabase structure, add data
• e.g., Marine Data Model tutorial