generalization web services

Generalization Web ServicesMoritz Neun

University of Zurich

Motivation

Generalization Web Services – Moritz Neun – 19. November 2007

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Motivation 1

Much progress of web cartography through OGC standards. WMS and WFS allow automated access and presentation of cartographic data Pre-calculation and usage of MRDB can support these services only partially

New requirements on delivering and generating on-demand and on-the-fly maps, containing more specific and tailor-made information

OGC (2002) has proposed Feature Generalisation Services, but no further developments yet


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Motivation 2

A large number of generalisation algorithms, auxiliary data structures, cartographic constraints and measures is developed and published

Isolated prototypes implemented with different programming languages

Integrated within closed monolithic systems(Clarity, ArcGIS, Genesys, ….)


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Motivation 2

Consequences: Benchmarks and comparison of algorithms difficult No reuse of available generalisation functionality

and support data structures - researchers have to start from scratch

Following that, rarely addressed “advanced questions” on the generalisation process such as combination of several operators, orchestration, …

Interoperable (research) platform for sharing of (generalization) functionalities needed

History


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History

Lehto and Kilpeläinen (2000, 2001)Edwardes et. al (2003)Badard and Braun (2003)Harrie and Johansson (2003)Sester et. al (2004),

Sarjakoski et. al (2005)Burghardt et. al (2005),

Neun et. al (2006, 2007)Regnauld (2006, 2007)Harrower and Bloch (2006)Lemmens et al. (2006),

Forster and Stoter (2006, 2007)

Open architectures based on distributed platforms have attracted significant interest in the generalisation community

•XSLT techniques are combined with Java programming for real-time generalisation

•Examples show two results of different XSLT processes with different generalisation functionality (selection and simplification)


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History

Lehto and Kilpeläinen (2000, 2001)Edwardes et. al (2003)Badard and Braun (2003)Harrie and Johansson (2003)Sester et. al (2004), Sarjakoski et. al (2005)Burghardt et. al (2005), Neun et. al (2006, 2007)Regnauld (2006, 2007)Harrower and Bloch (2006)Lemmens et al. (2006), Forster and Stoter (2006, 2007)


• Need for a common research platform in the domain of map generalisation was expressed

• Requirements for an open generalisation system• Related OGC developments were presented

(WMS, SLD, SVG, WFS, GML, FES, SOAP, WSDL, …)


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History



• OXYGENE platform developed at the COGIT laboratory of IGN

• Based on Java technology and different open source components

• Open source release in 2005


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History



• GiMoDig services based on layer architecture • Layers encapsulating data integration, data

transformation into GML, data processing (generalisation) and device dependent styling (portal layer)

• Further development of the approach from Lehto and Kilpeläinen with XSLT processing


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History



• WebGen platform • Accessible from different clients

(Web Browser, JUMP, …)• DEMO


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History

Lehto and Kilpeläinen (2000, 2001)Edwardes et. al (2003)Badard and Braun (2003)Harrie and Johansson (2003)Sester et. al (2004), Sarjakoski et. al (2005)Burghardt et. al (2005), Neun et. al (2005, 2007)Harrower and Bloch (2006)Regnauld (2006, 2007)Lemmens et al. (2006), Forster and Stoter (2006, 2007)


• MapShaper for browser based generalisation• Aim on interactive user controlled generalisation, no platform-independent

coupling of generalisation services• Strong relation of user interface and generalisation functionality

(limited flexibility - new generalisation functions requires new client versions)


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History



• Concept of system architecture for on-demand derivation systems• Usage of Geo-Ontologies to formalise input data, user requirements,

cartographic knowledge and service descriptions


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History



• Implementation based on OGC Web Processing Services

• Usage of profiles to describe syntax and the semantics of the operation


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History




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History

M.F. Goodchild (2005). GIS and modeling overview. In D.J. Maguire, M. Batty, and M.F. Goodchild, editors, GIS, Spatial Analysis, and Modeling. Redlands, CA: ESRI Press, pp. 1–18.

“There is also increasing interest in providing basic GIS services, such as geocoding, as remotely invokable methods implemented on the Web. In the next few years, dramatic improvements are expected in the availability of techniques for sharing methods and models.”

Web Services


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Web Service Technology

Generalization Services are Web Services: Client-Server structure Component architecture:

- encapsulation of functionalities and resources - generic interfaces (interface description) - loosely coupled by contract Platform independence: usage of standard web protocols (HTTP and XML) Interoperable Remote Procedure Calls (RPC)

(remote processing instead of data delivery)

Web Services are enabling interoperability


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Middleware Generalization ServicesTypical on-demand or on-the-fly generalization service for web map services: Used in combination with data services (e.g. WFS) Translator or compiler for converting and

combining datasets in order to be displayed Usually bound to one or multiple

specific and predefined data delivery services


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Toolbox Generalization Services

Various processing services provide their functionalities as distributed toolbox Data to be processed is provided by the user Everybody can present own services Platform

independentservice access

Coupling of different generalizationsystems

research platform WebGen framework

State-of-the-Art Toolbox Services


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State-of-the-Art

• WebGen research platform• Web Processing Services

• ArcGIS Server (ESRI)• SerAx (Axes Systems)

Toolbox-like service approachesfor remote processing

open commercial


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WebGen

Our prototype of a generalisation toolbox service framework Different plug-ins Generic interface

descriptions Registry for

service discovery Servers for

hosting differentalgorithms


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WPS

WPS Concepts from Foerster (2006)

Web Processing Service (OGC Draft)

Intended for many purposes not only generalisation

Raster and vector data Very open (and vague)

definitions of interface descriptions and data formats

Currently rather aproposal than areal standard

More concrete profileneeded for generalization


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WPS

Foerster (2006) shows WPS implementation for generalisation(partially adopted from WebGen)

Intended for working together e.g. with a web map server like geoserver but not as middleware (geoserver calls the WPS)

Provides ready generalised maps to the requesting client


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axpand

Generalsation functionsas internal services

Adopts WebGen concepts(registry & interface descriptions)

possible use of external services

Management of service workflows

Data is not sent in the service calls (remains in central database, only references are passed)

Uses service concept but rather closed and proprietary


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ArcGIS Geoprocessing Services

Geoprocessing services for the ESRI ArcGIS Server

All types of geoprocessing tools can be served

Works only with ArcGIS products and algorithms

Rather closed and proprietary commercial system

The WebGen Framework


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Implementation of the Toolbox Services Model: Various different distributed servers can provide

generalization services Generic interface

descriptions Registry for global

service discovery Services can use

other services(workflow)

Generalization Server

ServiceService

ServiceService


ServiceService

ServiceService


Registry Server

exec

ute

know

s


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Client plug-ins for different platforms Remote processing (execute)


ServiceService

ServiceService


ServiceService

ServiceService


JUMP GIS ClientPlug-in

Local data

AJAX Web ClientBrowser

Local data

Clarity Client

Plug-inLocal data

ArcGIS Client

Registry Server

query services

service descriptions

execute

execute


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WebGen Clients, Registry & Server

client server


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WebGen Registry


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WebGen Services

Large number of services available!


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WebGen Interface Descriptions

Generic XMLinterface descriptions: Nothing predefined

in the clients Dynamic adding of

new services Powerful also for

complex interfaces


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WebGen Client-Server Transfer


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Possible WebGen Scenario

LAN / InternetLAN / Internet

ServerJUMP

Server Plug-In

JUMP/JTSAlgorithms

ServerArcGIS

Server Plug-In

ArcGIS Toolbox

Workstation JUMP

local datasets

ToolboxPlug-In

Workstation ArcGIS

local datasets

ToolboxPlug-In

Workstation Clarity

local datasets

ToolboxPlug-In

ServerClarity

Server Plug-In

AGENTAlgorithms

Registry

coupling of systems for research or production

Generalization Service Categories


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MRDB

Generalization Service Categories

Gen

era

liza

tion

Serv

ices

Su

pp

ort

Serv

ices

Operator Services(simplification, aggregation, …)

service interface

interactive interface

Process Services(workflow control, evaluation)

service interface


Service Consumer(research, map production, …)

Support Services(attributes, triangulations …)

service interface



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Support Services

Provision of auxiliaryenriching information(data enrichment)

make structural knowledge explicit can be exploited by other services

differentiation by the output data type simple entities (geometries / attributes) complex relations (hierarchical / non-hierarchical)

Support Services

Entities(geometries, attributes)

Relations(hierarchical, non-

hierarchical)


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Operator Services

Operator services are implementing concrete generalization algorithms Perform geometrical and semantical transformations of map objects Can be context dependent by using structural knowledge (from support services)

Examples from building generalization:

RemovalSimplification Displacement


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Process Services

Workflow / orchestration of different services predefined batch workflows, adaptive workflows and fully automated systems: Selection of the appropriate algorithms

(operator services) for a situation Use of the right parameter values Application of operators in the proper sequence

simplifyinitial typify displace

Discussion


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Discussion

Strengths of the WebGen approach Provision of various functionalities as interoperable toolbox (research platform) Functional subdivision of generalization in

support, operator and process services Sharing, coupling and reuse of functionalities

at very different levels of granularity Provision of complex spatial data structures Central registry for service discovery Generic interfaces allow real interoperability Parallelization possible (clustering)


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Service Usage Scenarios

Keep in mind that different user types need different functionalities and levels of complexity: Novice user (planner wants to simplify a map) Expert user (NMA wants to couple systems) Researcher (wants to evaluate an algorithm) Data display (convert data from WFS on-the-fly)


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Where to start?

Challenges: Meet user scenarios Common generic (XML) service data model Generic syntactic and semantic interface descriptions needed (service capabilities and requirements) Granularity (especially of support services, stateless or stateful services)

Some work required (WebGen is still a prototype) Advance WebGen? Extend WPS with concrete profile?

Thank you!


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WebGen Registry

generalization web services

Documents

neun et

sester et

edwardes et

sarjakoski et

burghardt et

generalisation process

generalisation communityneed

domain of map generalisation