Workshop: Semantics in GDI

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June 26, 2003 GI-Tage 2003 Workshop

Workshop: Semantics in GDI

Werner Kuhn

Institute for Geoinformatics

[email protected]

June 26, 2003 Semantics in GDI 3

Goals

To work towards a better understanding of semantic problems in a GDI

To exchange information on use cases To exchange experiences with methods and tools

This is not a tutorial on semantic technologies – your contributions and questions are requested throughout the workshop.


Overview

1. The problem Use case Analysis Generalization

2. Solution attempts Puzzle pieces Putting the pieces together Puzzling questions


The Problem: a use case

Shortest path for oversized vehicle


Perspective of a Service Developer

Input:• two locations: origin and destination

e.g., end of A43 to Schloss in Münster • vehicle and load specifications

total width, weight, min. radius for turns• other constraints

time, cost, safety

Output:• shortest path satisfying (some of) the constraints• driving instructions


Searching for information

Road data• local government: MS_Strassen• state: ATKIS• industry: TeleAtlas MultiNet (GDF)

Navigation services• wayfinding web services: lack information• shortest path services: not available online• re-use existing local code (shortest path)• service chain with filter on graph


What information can the data provide?Ergebnisse der erweiterten Suche:

XtraWMS - GDI Testbed IMapping Service: Straßendaten im NetzBeschreibung: Xtra Web Map Server von interactive instruments bereitgestellt für das GDI Testbed I. Der Server präsentiert das Netz der klassifizierten Straßen basierend auf dem OKSTRA-Standard im Bereich von sechs TK-Blättern im Raum Düsseldorf. WMS (1.1.0)Dienst erstellt: 2001-09-08 18:45:00Kontaktinteractive instruments GmbH, Reinhard Erstling, Geschäftsfü[email protected] Straße 70-7253115 BonnNRW, GermanyLage zeigenShowOperationsOnline Ressource aufrufenDer Zugang zu diesem Dienst ist nicht kostenpflichtig.

mailto:[email protected]

http://klotho.interactive-instruments.de/cgi-bin/XtraWMS?


From data files and documentation

MS_Strassen• polylines, a few attributes

ATKIS• ATKIS OK

several hundred pages, human-readable, online

• Teil D3 Verkehr: Objekttyp 3101 Strasselinienförmig

GN Geographischer NameBRF Breite der Fahrbahn “…setzt sich zusammen aus den Breiten der Fahrstreifen, der befestigten Rand-/Leitstreifen sowie der Stand- oder Kriechspuren (befestigte Straßenoberfläche)”

BRV Breite des Verkehrsweges“…Abstand der seitlichen Begrenzungslinien entsprechend der Objektdefinition in Form der jeweils oberen Grenzen der o.a. Klasseneinteilung”

...


From data files and documentation (2)

TeleAtlas MultiNet• ISO Standard GDF (Geographic Data Files)

ca. 700 pages, to purchase from DIN

• Release Notes MultiNet Germany34 pages, to purchase with product

• MultiNet Data Specifications1249 pages, to purchase with product

• Roads and FerriesWidth (in cm): „The width of a Road Element ..., a lane or a Road Furniture or Structure Feature.“

Maximum Width Allowed (in cm): „The maximum width limit of a vehicle that may use the Road Element, ... The limit is normally set by a physical obstruction such as a bridge or a legal restriction.“

• Both attributes are not implemented in MultiNet


What‘s left?

Take • road axes from GDF• road width (BRF) from ATKIS

Obtain both data sources• try to read them in your GIS• licensing

Build service architecture Build navigation service

12 Semantics in GDIJune 26, 2003

ATKISGDF MulitNet

Middleware

Servlet Engine

Web Feature Server

Middleware

Servlet Engine

Web Feature Server

WFS ClientFilter ServiceNavigation Services

Navigation Client (Browser)

GML

Java FeatureCollectionJava FeatureCollection

HTMLOpenGIS Components

Architecture for Multi-source Navigation Chain


Caveats

„schema integration“, „data integration“ „data interoperability“ Semantics of road width Semantics of passable Information Communities vs. natural languages Feature identity in geographic data Data quality (completeness, currency, ...)


A Summary of Semantic Problems

Specify the meaning of the question• „passable for oversized transport“: width? turns? weight? noise?

Find data with potentially useful contents• ATKIS, ALKIS, GDF, OKSTRA, ...

Find services with potentially useful functionality• shortest path, filter, ...

Determine the meaning of feature classes• road, „komplexe Strasse“, ...

Determine the meaning of attributes• „Breite der Fahrbahn“, „Breite des Verkehrsweges“, „maximum width allowed“

Determine the meaning of service operators• shortest path

Semantic interoperability problems

e.g., building heights from floors

e.g., directions from graphs e.g., parcels touching a road

data-service service-service service-user


Solution Attempts

A vision Pieces of the puzzle

• Metadata• Catalog services• Ontologies• Reasoning systems• Semantic translators


Vision

Users of geographic information should be able to refer thematic data to semantic reference systems, just as they refer geometric data to spatial reference systems.

Software should support the referencing process projections to simpler semantic spaces semantic translation among different reference systems.


Semantic Reference Systems

Spatial Reference System [ISO 19112]

„system for identifying positions in the real world“e.g., geodetic reference systems

Temporal Reference System [ISO 19108]

„basis against which time is measured“e.g., calendars

Semantic Reference System [t.b.d.]

basis on which thematic data are interpreted:‚forest‘, ‚wetland‘‚ ‚road width‘ etc.e.g., ontologies


Semantic Reference Systems

Methods and tools for referencing GI terms by

• grounding (e.g. “move”)

• projecting (e.g. ferries and roads to edges)

• translating (e.g. cadastre to navigation)


What we have today

multiple semantic reference systems• explicit (ontologies, FACs)• implicit (in data models, programs, procedures)

a proliferation of tools (e.g., XML-based)• exposing semantics (“mark-up language du jour”)• designing representation before computation (Roman numerals)

unclear theoretical bases• ontologies are theories without testable models• they often lack a (sound) typing system and/or axioms• upper levels are ill-defined

need for theory and tools:• explaining the meaning of terms in (geographic) information• to integrate (geographic) information from different sources


Ontologies: specifications of concepts in a domain

CAP landuse code CAP landuse label

1 Urban

1.A Urban; Residential

1.A.0.a Urban; Residential; Single family

... ...

#| ATKIS-Objektartenkatalog (ATKIS-OK) | Seite Blatt | Stand |#| Teil D1: ATKIS-OK 25 | 62.1 1 ( 2) | 01.11.1995 |#|______________________________________|________________|____________|#| Nr. Objektbereich | Nr. Objektgruppe |#| 6000 RELIEF | 6200 Besondere Geländeoberflächenformen |#|____________________|_______________________________________________|#| Nr. Objektart | Nr. |#| 6201 Damm, Wall, Deich | 6201 |#|_____________________________________________________________|______|

[Visser et al.]


clc: CORINE Land Cover categories

1.2 Industrial, commercial and transport units

1.2.1 Industrial or commercial units

1.2.2 Road and rail networks & associated land

1.2.3 Port areas

1.2.4 Airports

1.4 Artificial, non-agricultural vegetated areasCO

RIN

E L

and

Cov

er


What it takes

Spatial and temporal reference systems have•well-known systems of measures and units

e.g, lengths, angles, time

•well-known algebras for these measures e.g., modulo arithmetic for angles

•tools for projection and transformatione.g., map projections, coordinate transformations

Semantic reference systems need •formalizations of the kind that Descartes provided for space

using algebraic specifications (equational theories)

•mappings among the resulting formal systemsusing category theory (morphisms)


An ontology editor: Protégé

entity-relationship modeling based on frame logic pre- and post-conditions for operators interface to Java open source good usability unclear theoretical bases

• classes vs. Instances (vs. Java classes), • contents of pre- and post-conditions


:THING •:SYSTEM-CLASS

•:CLASS •:STANDARD-CLASS

•:SLOT •:STANDARD-SLOT

•:FACET •:STANDARD-FACET

•:CONSTRAINT •:PAL-CONSTRAINT

•:ANNOTATION •:INSTANCE-ANNOTATION

•:RELATION •:DIRECTED-BINARY-RELATION

•Coordinate •AttributeInstanceCollection

•FeatureAttributeInstanceCollection •RoadsAndFerriesInstanceCollection

•NestedFeature •Level_0

•Node •Edge

•NestedEdge •Level_1

•LineFeature •PointFeature •Junction •LineElement

•FerryConnection •RoadElement

•Level_2 •ComplexFeature •Road •Ferry •Intersection


Class Level_2

Abstract Class Extends :THING

Direct Instances:

None

Direct Subclasses: 1.ComplexFeature 2.Road 3.Ferry 4.Intersection


DAML-S: a proposal for a service description language

Building on OWL (formerly DAML+OIL) to deliver the semantics missing in WSDL and other

syntactic service descriptions (IDL) service profiles with model-based pre- and post-

conditions based on RDF Clearly a language for exposing semantics Unclear:

• relationship to domain ontologies?• kinds of models to be used?


Our tool: Haskell

a modern functional language• executable• strict type system• multiple parameter type classes (Hugs dialect)• freely available from www.haskell.org• translates nicely into Java (interfaces)

in a nutshell• algebraic data types: data Car = Car Position• type classes: class LocatedAt object location where

location :: object -> location • instances: instance LocatedAt Car Position where

location (Car pos) = pos


An Example: Ferries in GDF

+navigate()

Edge

+drive()

Road

+cross()

Ferry

level 0

level 1


Ferry example: objectives

1. apply the idea of semantic reference systems to a simple example

2. build a semantic reference system

3. demonstrate the use of Haskell as an ontology language

4. test the hypothesis of what went wrong

5. relate to cognitive semantics: affordances, image schemata, blending


Layers of Semantic Reference

Contents Form

application data model data types

application objects data

reference frame upper-level ontology

symbol grounding (outside the system)

semantic reference application ontology


Application Data Model: GDF roads

Nodes have Namesdata Node = Node Name

Edges connect two Nodesdata Edge = Edge Node Node

RoadElements follow Edgesdata RoadElement = RoadElement Edge

FerryConnections follow Edgesdata FerryConnection = FerryConnection Edge


Application Data Model: Vehicles

Cars have a Node as locationdata Car = Car Node

CarFerries carry multiple Cars and have a Node locationdata CarFerry = CarFerry [Car] Node


Application Objects

road networkstart = Node "start"

end = Node "end"

theEdge = Edge start end

theRoadElement = RoadElement theEdge

theFerryConnection = FerryConnection theEdge

vehiclestheCar = Car start

theCarFerry = CarFerry [theCar] start


Reference Frame: Basics

named objectsclass Named object name where

name :: object -> name

named objects are equal if their names are equalinstance (Eq name, Named object name) => Eq object where

object1 == object2 = (name object1) == (name object2)

located objectsclass LocatedAt object location where

location :: object -> location


Reference Frame: Image Schemas

a simple link schemaclass Link link object where

from, to :: link -> objectother :: link -> object -> objectother link object | object == from link = to link

| object == to link = from link| otherwise = error "not linked"

a simple path schemaclass Path path object where

move :: path -> object -> object


Reference Frame: Image Schemas (2)

a simple surface schemaclass Surface surface object where

putOn :: object -> surface -> surfacetakeOff :: object -> surface -> surfaceisOn :: object -> surface -> Bool

conveyances for transportationclass (Path path conveyance, Surface conveyance object) => Conveyance conveyance path object where

transport :: path -> conveyance -> object -> object


Symbol Grounding: Assumptions

Haskell language semantics • Data types (Strings, Lists, ...)• Operational semantics

experiential grounding of image schemas


Semantic Reference (1)

RoadElements are Paths for Carsinstance Path RoadElement Car where

move (RoadElement edge) (Car node) = Car (other edge node)

FerryConnections are Paths for CarFerriesinstance Path FerryConnection CarFerry where

move (FerryConnection edge) (CarFerry cars node) = CarFerry (doToAll (transport (FerryConnection edge)

(CarFerry cars node) cars) (other edge node)


Semantic Reference (2)

CarFerries are Surfaces for Carsinstance Surface CarFerry Car where

putOn car (CarFerry cars node) = if (location car == node) then CarFerry (addOne car cars) nodeelse error "Car and CarFerry are not co-located"

...

CarFerries are Conveyances for Carsinstance Conveyance CarFerry FerryConnection Car where

transport (FerryConnection edge) carFerry (Car node) = Car (other edge node)

...


Layers of Semantic Reference

Contents Form

application data model data types

application objects data

reference frame upper-level ontology

symbol grounding (outside the system)

semantic reference application ontology


Ontology Testing (1)

the car is at the end of the road element after moving t1 = location (move theRoadElement theCar) == end

the ferry is at the end of the ferry connection after movingt2 = location (move theFerryConnection theCarFerry) == end

the car is at the end of the ferry connection after being transported by the ferryt3 = location (transport theFerryConnection theCarFerry theCar) == end

the car cannot move on the edge or on the ferryConnectiontype in: move theEdge theCar type in: move theFerryConnection theCar


Semantic Projection

+navigate()

Edge

+drive()

Road

+cross()

Ferry

pro

ject

ion

+navigate()

Edge


Ontology Testing (2)

Erroneous Semantic Translation

edges are paths for cars instance Path Edge Car where

move edge (Car node) = Car (other edge node)

after adding this axiom, move theEdge theCar

executes (but the car is not supposed to move on any edge, as it may be a ferry connection)


Conclusions on Solution Attempts Current standards proposals focus on exposing semantics Lack of theories and tools for semantic modeling Spatial reference systems motivate semantic reference systems

• shown example for a simplified navigation domain• implemented semantic referencing, projection, and translation• from static ontologies to computational reference systems

Upper-level ontology with meaningful abstractions• image schemas: processes in space and time• actions afforded by objects in the environment

properties are modeled as functions inherited from classes• type classes specify wrappers for legacy data• transportation is a blending of the path and surface schemas.


In progress

1. evolving upper-level ontology for GI• organized as a lattice of type classes• with multiple inheritance of behavior

2. semantic interoperability applications• environmental planning• emergency management• storm damage assessment• transportation models (topographic to navigation)

3. comparisons with and translation to other approaches• description logic approaches (e.g., BUSTER)• DAML-S and OWL• OBJ• ...


For more information...

MUSIL web site (Muenster Semantic Interoperability Lab):http://musil.uni-muenster.de

recent publications (all at MUSIL web site)• Implementing Semantic Reference Systems. AGILE 2003 • Semantic Reference Systems. Guest Editorial, International Journal of

Geographical Information Science (in print).• Modeling the Semantics of Geographic Categories through Conceptual

Integration. GIScience 2002. LNCS 2478: 108-118.• Ontologies in support of activities in geographical space. International

Journal of Geographical Information Science 15(7): 613-631.

Workshop: Semantics in GDI

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