semantic evolution of geospatial web services: use cases and

Semantic Evolution of GeospatialSemantic Evolution of GeospatialWeb Services:Web Services:

Use Cases and Experiments in theUse Cases and Experiments in theGeospatial Semantic WebGeospatial Semantic Web

Joshua Lieberman, Todd Pehle, Mike Dean

Traverse Technologies, Inc.,

Northrop Grumman Information Technology / TASC,

BBN Technologies

© 2004 Traverse Technologies Inc.

OverviewOverview

♣Geospatial information and OpengeospatialWeb Services

♣Geospatial Semantic Web, aninteroperability experiment

♣Semantic challenges on the Spatial Web


What are OGC and OWS ?What are OGC and OWS ?♣ “The Open Geospatial Consortium, Inc. (OGC) is a non-profit,

international, voluntary consensus standards organization that isleading the development of standards for geospatial and locationbased services”

♣ “Opengeospatial Web Services” (OWS) - OGC has been developingfor some time specifications for a suite of Web services (sensulato) and associated encodings to expose geospatial content andoperations from distributed content repositories to remoteclients across diverse platforms:♣ GML - geographic markup language (an information model and XML

schema) for encoding features (geometric representations of geography).♣ Web Feature Service - service providing access to collections of features♣ Web Map Service - service providing access to map layers

(cartographically rendered features and images)♣ Catalog Service / Web - service supporting (spatial) discovery of

geospatial datasets and services♣ Several other associated specifications


1) GSW Background1) GSW Background♣ Geospatial Semantic Web: Use of Semantic Web technologies to

discover and reason on geospatial information (UCGIS, Egenhofer,Sheth, etc.)

♣ GSW broad research activity sponsored by National GeospatialIntelligence Agency (NGA), undertaken by a number of investigators

♣ Interoperability experiment: an Open Geospatial Consortium(OGC) -sanctioned member collaboration to test or refine OWS specifications

♣ This “GSW IE”: activity proposed by NGA, NGIT/TASC, and BBN totest and refine OGC(+) specifications within a scenario for geospatialquery with formal semantics:♣ Web Feature Service (WFS) and Filter Encoding (FE)♣ Geography Markup Language (GML)♣ ISO 19115 / 19119 / 1910n / FGDC feature metadata (ISO)

♣ Other initial participants: SCO, Jaume I, Muenster, Galdos, GMU, …


Drilling Down:Drilling Down:

♣ The Geospatial part♣ Maps and map visualization♣ Features and feature geometries♣ Geographic and other relationships

♣ The Web part♣ Distributed data - “maintain locally / access globally”♣ Shared services, loosely or tightly coupled to geodata♣ Interoperability between technologies, vendors, architectures

♣ The Semantic part♣ Interoperability between communities and domains♣ Softer software♣ Automated reasoning and inference


Geospatial Reasoning: 2-D and BeyondGeospatial Reasoning: 2-D and Beyond

♣ Coordinate relationships♣ Scale significance♣ Coordinate reference systems

♣ Topological relationships♣ Network♣ Overlay

♣ Spatial inference♣ Proximity♣ Continuity♣ Representation♣ Dimensionality♣ Temporality


The Web Changes Everything (Geospatial)The Web Changes Everything (Geospatial)

♣ Global communities for local geography

♣ Distributed information networks

♣ Premium on interoperability

♣ The GIS dialtone

♣ Maintain locally, access globally

♣ Currency is the currency

♣ (non-GIS) barbarians are at the (GIS) gate


Role of interoperability / opening the templeRole of interoperability / opening the temple

♣ Focuses on sustained operability - today and the next day♣ Permits separation of concerns♣ Supports information portability♣ Allows component interchangeability♣ Contributes to transparency, testability, and trust♣ Layers of interoperability build on one another♣ Stable syntax promotes shared semantics / understanding♣ Standards are necessary but not sufficient for

interoperability


2) Interoperability experiment: goals2) Interoperability experiment: goals

♣ Exercise current semantic technology in a geospatial realm

♣ Demonstrate an end-to-end geospatial semantic query♣ Utilize multiple ontologies for Geointel operations♣ Develop OGC service descriptions with formal semantics

(e.g. OWL-S description for Web Feature Service)♣ Develop and test Semantic Web Services interface / role for

OGC services♣ Enhance interoperability in a distributed, heterogeneous

world, or at least identify the problems


““TypicalTypical”” Geospatial Query Geospatial Query(Intelligence / Logistics Domain)(Intelligence / Logistics Domain)

“Which airfields within 500 miles of Kandahar support C5A aircraft?”

Aero Feature orGeo Feature?

Buffer orproximity?

Statutory or Nautical?Straight-line or driving?Coordinate system? Afghanistan?

Centroid or outline?

What does thismean?

Featureproperty ornon-spatialinformation?


Sequence of Experimental TasksSequence of Experimental Tasks

Link Ontologies into Knowledgebase

Generate and Visualize OWS (WFS) Queries

Request Remote Service Descriptions

Process Queries Through Knowledgebase

Compose Queries and Query Templates

Generate and Distribute Sub-queries

Identify and Build Ontologiesfor Geospatial / GeoIntelDomains


Multiple GSW Ontology ComponentsMultiple GSW Ontology Components

GeoIntelProblem Domain

Ontology

Base Geospatial Ontology

NGA Feature Ontology

OGC ServicesOntology

Other Base Ontologies


Initial ECDM Selections for ExperimentInitial ECDM Selections for Experiment

Airport

RunwayTaxiway

Apron

ObstructionThreshold

Route

Plane

Itinerary

RepairWeather

Nav AidsService

Fuel

Lighting

VOR

NDBILS

MLS

TACAN


““TypicalTypical”” GSW Query Stack GSW Query Stack

♣ Query / Visualization Client

♣ Query Translator

♣ Query Processor

♣ Graph Store / Inferencer

♣ Geospatial Inferencer

♣ Remote WFS harvester

♣ Remote WFS translator

♣ Remote WFS

♣ Do CSW query, then WFS query

♣ Translate GetRecord to semantic query

♣ Process semantic query

♣ Query knowledgebase

♣ Resolve geospatial relations

♣ Add WFS descriptions to knowledgebase

♣ Translate between GML / XML & OWL

♣ Provide GML features through WFS interface

Standardized Web Services interfaces can be (or have been)defined between any two of these stack elements

Element Function


Model Query Model Query ““PlanPlan””

Question

Template

Query Rules & Artifacts

Knowledge Base

Reasoning & Inference

Domain Ontology

Ontologies

RemoteWFS

WFS Get

Feature

Local Ontologies

Visualizer

Map

KnowledgeServer

Knowledge Server

Sub-query

ServiceResponse

Query ClientVisualization

Client


GEOINT Query Plan HasGEOINT Query Plan Has……♣ Concepts/Relationships, e.g. OWL

ontology elements♣ Rules, e.g. RuleML (SWRL)♣ Completion Criteria, e.g. SeRQL

query elements♣ (precondition) Inference-based

knowledge refinement♣ (precondition) Traversal of geospatial

relationships♣ (precondition) Access to remote

services through semantic servicedescriptions

Question

Template

Query Rules

Domain Ontology

Query Client


(Some) Technology Options(Some) Technology Options

ArcGIS / Gaia

SemanticFeatureVisualizerPlugin

SemanticQueryPlugin

DbSAIL WebSAIL

GeoSAIL

Query Layer (SeRQL)

HTTP API

Sesame ProcessingFramework

DamlDB

WFS

JavaTopologyServices

Templates

REP API GRAPH API

Oracle 10g


OWL-S Service Description Components andOWL-S Service Description Components andQuestionsQuestions

Type of Service

Themes of Content

Provider / business terms

Content Description

Service Bindings / Messages

Bound Parameters

Service Quality

Smart Service Consumption

Service Composition

Service Profile

Service Grounding

Service Model

Feature Schema

Content Domain

Feature Individuals

?


3) Semantic service description: the missing3) Semantic service description: the missingbitsbits

♣ <<Content>> description♣ Profile (e.g. ISO 19115)

♣ Grounding (bound parameters)

♣ Model (e.g. GML, ISO 19110)

♣ Interface for query ofservice description

♣ Progressive generalization♣ Discovery♣ Binding♣ Domain♣ Dictionary♣ Individual / Instance

♣ Description of service self-description


ObservationsObservations♣ The geospatial realm has well-developed information and service

models, but mainly implicit semantics♣ Within the geospatial realm are many communities with only

partially shared vocabularies.♣ Gradual adaptation of the existing data and infrastructure is

essential♣ Geospatial content is (necessarily) scale-dependent, distributed,

heterogeneous, and dynamic - a challenge for description /generalization

♣ Geospatial services are typically tightly coupled to content♣ Resolution / traversal of geospatial relationships is a computational

challenge♣ Semantic Web Services are essential for opening up the “geospatial

temple cult” but must avoid exchange of one cult for another

semantic evolution of geospatial web services: use cases and

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