First steps towards formalizing generalization operators a topdown approach

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First steps towards formalizing generalization
operators -a top-down approach

• Theodor Foerster
• 13 July 2007, ifgi, Muenster

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Overview

• Introduction motivation
• Classification framework
• Model generalization operators
• Cartographic generalization operators
• Outlook
• Current questions

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Introduction

• Introduction motivation
• Classification framework
• Model generalization operators
• Cartographic generalization operators
• Outlook
• Current questions

• Generalization
• The adaptation of geo-data according to user and
  use requirements
• Model generalization (? data)
• Cartographic generalization (? maps)
• Generalization process consists of different
  generalization operators

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Generalization operators

• Introduction motivation
• Classification framework
• Model generalization operators
• Cartographic generalization operators
• Outlook
• Current questions

• Provide an abstract description of generalization
  functionality
• Important to abstract human knowledge
• Allows comparing generalization functionality
• An operator is implemented by different
  algorithms
• Operators are not interfaces!

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Motivation

• Introduction motivation
• Classification framework
• Model generalization operators
• Cartographic generalization operators
• Outlook
• Current questions

• Different classifications are available
• Do not cover all aspects
• Project-driven
• Not formal
• Classification is important
• For enabling automated web-based generalization
  processing
• Transparency for evaluation
• Knowledge exchange
• Producing on-the-fly base maps for different
  scenarios on the Web
• RGI 002 DURP ondergronden project
  (www.durpondergronden.nl)

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Gruenreich model

• Introduction motivation
• Classification framework
• Model generalization operators
• Cartographic generalization operators
• Outlook
• Current questions

Reality
Object generalization
Model generalization
Primary model
Cartographic generalization
Cartographic model
Inspired by Gruenreich (1992), ATKIS - a
topographic information system as a basis for GIS
and digital cartography in Germany
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Classification framework

• Introduction motivation
• Classification framework
• Model generalization operators
• Cartographic generalization operators
• Outlook
• Current questions

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Model vs. cartographic generalization operators

• Introduction motivation
• Classification framework
• Model generalization operators
• Cartographic generalization operators
• Outlook
• Current questions

• Model generalization operators can be defined on
  feature type level
• Cartographic generalization operators are defined
  on feature instance level
• Both are applied on feature instance level!

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Operator classification

• Introduction motivation
• Classification framework
• Model generalization operators
• Cartographic generalization operators
• Outlook
• Current questions

• Identified operators are based on literature

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ISO 19109

• Introduction motivation
• Classification framework
• Model generalization operators
• Cartographic generalization operators
• Outlook
• Current questions

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Model generalization operators

• Introduction motivation
• Classification framework
• Model generalization operators
• Cartographic generalization operators
• Outlook
• Current questions

• Class Selection
• Reclassification
• Collapse
• Combine
• Simplification
• Amalgamation

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Collapse Combine

• Introduction motivation
• Classification framework
• Model generalization operators
• Cartographic generalization operators
• Outlook
• Current questions

• Changing the geometry type
• Collapse
• Decrease dimensionality
• Example Collapse road polygons to road lines
• Combine
• Increase dimensionality
• Goes along with reclassification
• Example Combine leisure sites (modeled as
  points) to touristic attraction (modeled as
  polygon)

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Simplification Amalgamation

• Introduction motivation
• Classification framework
• Model generalization operators
• Cartographic generalization operators
• Outlook
• Current questions

• Simplification
• Mainly used for data reduction
• Deletes aspects of the feature
• Not that invasive
• Amalgamation
• Amalgamating a group of features to a new feature
  of same geometry type
• Goes along (mostly) with reclassification
• Example Merging adjacent polygons of different
  types of forest to a new feature of type forest.

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Role of symbolization

• Introduction motivation
• Classification framework
• Model generalization operators
• Cartographic generalization operators
• Outlook
• Current questions

• Exclude symbolization from the cartographic
  generalization process
• Cartographic generalization is always applied on
  symbolized (cartographic) features

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OGC GO-1 application objects

• Introduction motivation
• Classification framework
• Model generalization operators
• Cartographic generalization operators
• Outlook
• Current questions

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Cartographic generalization operators

• Introduction motivation
• Classification framework
• Model generalization operators
• Cartographic generalization operators
• Outlook
• Current questions

• Enhancement
• Displacement
• Elimination
• Typification
• Amalgamation

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Examples cartographic generalization operators

• Introduction motivation
• Classification framework
• Model generalization operators
• Cartographic generalization operators
• Outlook
• Current questions

Displacement
Amalgamation
Elimination
Enhancement
Typification
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Outlook

• Introduction motivation
• Classification framework
• Model generalization operators
• Cartographic generalization operators
• Outlook
• Current questions

• Verifying classification by interviews with NMAs
• Harmonizing model generalization and schema
  translation
• Research collaboration with Lassi Lehto _at_ FGI
• Extracting implementing a formal description of
  the operators

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Current questions

• Introduction motivation
• Classification framework
• Model generalization operators
• Cartographic generalization operators
• Outlook
• Current questions

• How to formalize the proposed operators?
• Operators are not interfaces (syntax is missing)
• Relation to schema translation?
• Model generalization provides the geometric tools
  for schema translation