Semantic Evolution of Geospatial Web Services: Use Cases and Experiments in the Geospatial Semantic Web Joshua Lieberman, Todd Pehle, Mike Dean Traverse

Semantic Evolution of Geospatial Semantic Evolution of Geospatial Web Services:Web Services:

Use Cases and Experiments in the Use Cases and Experiments in the Geospatial Semantic WebGeospatial Semantic Web

Joshua Lieberman, Todd Pehle, Mike DeanTraverse Technologies, Inc.,

Northrop Grumman Information Technology / TASC, BBN Technologies

© 2004 Traverse Technologies Inc.

OverviewOverview

Geospatial information and Opengeospatial Web Services

Geospatial Semantic Web, an interoperability 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 is leading the development of standards for geospatial and location based services”

“Opengeospatial Web Services” (OWS) - OGC has been developing for some time specifications for a suite of Web services (sensu lato) and associated encodings to expose geospatial content and operations from distributed content repositories to remote clients 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 Geospatial Intelligence 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 to test and refine OGC(+) specifications within a scenario for geospatial query 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


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

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

Aero Feature or Geo Feature?

Buffer or proximity?

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

Centroid or outline?

What does this mean?

Feature property or non-spatial information?


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 Ontologies for Geospatial / GeoIntel Domains


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

AirportAirport

RunwayRunway

TaxiwayTaxiwayApronApron

ObstructionObstructionThresholdThreshold

RouteRoute

PlanePlane

ItineraryItinerary

RepairRepair

WeatherWeather

Nav AidsNav AidsServiceService

FuelFuel

LightingLighting

VORVOR

NDBNDBILSILS

MLSMLS

TACANTACAN


““Typical” GSW Query StackTypical” 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 “Plan”Model Query “Plan”

Question

Template

Query Rules & Artifacts

Query Rules & Artifacts

Knowledge Base

Reasoning & Inference

Domain Ontology

Ontologies

RemoteWFS

WFS Get

Feature

Local Ontologies

Visualizer

Map

KnowledgeServer

Knowledge Server

Sub-query

Service Response

Query ClientVisualization

Client


GEOINT Query Plan Has…GEOINT 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 service descriptions

Question

Template

Query Rules

Query Rules

Domain Ontology

Query Client


(Some) Technology Options(Some) Technology Options

ArcGIS / Gaia

Semantic Feature Visualizer Plugin

Semantic Query Plugin

DbSAIL WebSAIL

GeoSAIL

Query Layer (SeRQL)

HTTP API

Sesame Processing Framework

DamlDB

WFS

Java Topology Services

Templates

REP API GRAPH API

Oracle 10g


OWL-S Service Description Components and OWL-S Service Description Components and QuestionsQuestions

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 missing 3) Semantic service description: the missing bitsbits

<<Content>> description Profile (e.g. ISO 19115) Grounding (bound parameters) Model (e.g. GML, ISO 19110)

Interface for query of service 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

Documents

Semantic Evolution of Geospatial Web Services: Use Cases and Experiments in the Geospatial Semantic Web Joshua Lieberman, Todd Pehle, Mike Dean Traverse