ica tutorial on generalisation & multiple representation 4 august 2007 moscow t6: generalisation...

ICA Tutorial on Generalisation & Multiple Representation

4 August 2007 Moscow

T6: Generalisation and Web Services

Dirk BURGHARDT & Moritz NEUNInstitute of Geography – University of Zurich

ICA COMMISSION ON GENERALISATION AND MULTIPLE REPRESENTATION4 August 2007 Moscow

LECTURE 6© D. Burghardt & M. Neun, 2007

Agenda

Motivation for Generalisation ServicesHistoryDefinition & TypologyState-of-the-ArtWebGenDemoConclusion



Motivation

Much progress of web based cartography through standards developed by the Open Geospatial Consortium (OGC)Automated access and presentation of cartographic data standardised through Web Feature Services (WFS) and Web Map Services (WMS)Pre-calculation and usage of MRDB can support these services partiallyNew requirements on delivering and generating on-demand and on-the-fly maps, containing more specific and tailor-made informationOGC (2002) has expressed interest on Feature Generalisation Service, but services for automated generalisation are not standardised yetNeed for platform independent sharing of generalisation methods



Motivation

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, ….)



Motivation

Consequences:Benchmarks and comparison of algorithms difficultNo 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, …



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)



History



• 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, …)



History



• OXYGENE platform developed at the COGIT laboratory of IGN

• Based on Java technology and different open source components

• Open source release in 2005



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



History



• WebGen platform • Accessible from different clients

(Web Browser, JUMP, …)• DEMO



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)



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



History



• Implementation based on OGC Web Processing Services

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



History





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.”



Generalisation Services

Definition of Generalisation Services




What is a web generalisation service ?“A web generalisation service is a software system designed to exchange interoperable machine-to-machine and machine-to-human generalisation functionality over a network. It has an interface described in a machine-processable format … .”



Data Delivery Services

Most common and evident type of geographical servicesProvides all sorts of geographical informationStandards available (e.g. OGC WMS and WFS)



Generalisation Middleware Services

Are used in combination with data delivery servicesMiddleware services act as sort of translator or compiler which can convert and combine datasets to be sent to the requesting clientUsually are bound to one ore multiple specific and predefined data delivery services



Generalisation Toolbox Services

Data to be processed is provided by the userEverybody can present own servicesServices are be accessed in a platform independent way allows coupling of different generalisation systems



Typology of Generalisation Services

Generalisation process service

Generalisation operator service

Generalisation support service

Human service consumer

process service(workflow control, orchestration)

operator service(simplification, smoothing, …)

support service(triangulation, topology, …)

service consumer(research, map production)

interactive interface

interactive interfaceservice interface

service interface

MRDB(support information)

service interface interactive interface




Web Service TechnologyService Oriented Architectures as Evolution of Distributed Computing



Web Service Introduction

Web Services vs. Web Pages– Web browser as client requests a HTML page from a server– Browser only displays the page but can not understand the contents

user has to read and understand the data– Other software like a GIS can not simply access data or functionalities

provided as HTML pages (no machine-machine inter-process communication)

Web Services are designed to support interoperable Machine-to-Machine interaction over a network

Browser(browser displays

HTML)

Server(returns HTML

page)

get page

return page



Web Service Characteristics (1)

Client - Server architecture– Service request / response / exception– Allows data exchange and inter-process communication (Remote Procedure

Calls, RPC)

Client(idle waiting for

results)

Client(idle waiting for

results)

Server(returns

requested data)

Server(executes procedure)

invoke procedure (send parameters)

return results

query data

return data

Data retrieval:

Execution of remote procedures:



Web Service Characteristics (2)

Component architecture– Components (= services) are encapsulating a set of functionalities and

resources, interact with other components (emerges from object-oriented technology)

– Components have generic interfaces through which they advertise their functionalities

– Services are usually loosely coupled by the “contract” of the interface description

n-tier distribution – Services can be used by higher level services– Services can themselves use the functionality of others

Platform independence– Web protocols (HTTP and XML) allow easy integration of heterogeneous

environments– HTTP and XML are available for every major platform



n-tier Middleware Service

GiMoDig service architecture (from Harrie, 2005)

Typical middleware service:Middleware layers is between datalayer and clientOn-the-fly processing Usually predefined data sources and data flows (homogeneous architecture)



Toolbox Services

Ideal of a toolbox service:Data is processed on a remote serverData to be processed provided or specified by the userStandards based communication between client and server platform independentclient plug-ins for different mapping systems




State-of-the-ArtToolbox Generalisation Services



State-of-the-Art

• WebGen research platform• Web Processing Services

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

Toolbox-like service approachesfor remote processing

open commercial



WebGen

Our prototype of a generalisation toolbox service frameworkDifferent plug-insGeneric interfacedescriptionsRegistry forservice discoveryServer forhosting differentalgorithms



WPS

WPS Concepts from Foerster (2006)

Web Processing Service (OGC Draft)Intended for many purposes not only generalisationRaster and vector dataVery open and vague definitions of interface descriptions and data formatsCurrently rather aproposal than areal standard



WPS

Foerster (2006) shows WPS implementation for generalisation(partially adopted from WebGen)Intended for working together e.g. with a web map server like geoserverbut not as middleware (geoserver calls the WPS)Provides ready generalised maps to the requesting client



axpand

Generalsation functionsas internal servicesAdopts WebGen concepts(registry & interface descriptions)possible use of external servicesManagement of service workflowsData is not sent in the service calls (remains in central database, only references are passed)

Uses service concept but rather closed and proprietary



ArcGIS Geoprocessing Services

Geoprocessing services for the ESRI ArcGIS ServerAll types of geoprocessing tools can be servedWorks only with ArcGIS products and algorithms

Rather closed and proprietary commercial system



The WebGen Framework

Client-serverarchitectureJava-based server for providing variousalgorithms (not onlyin Java)Client plug-ins for different platformsRegistry for service discoveryGeneric interface descriptions

Can be used as generalisation research platform



WebGen Client-Server System



LAN / InternetLAN / Internet

Possible Scenario

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




WebGen Demo



Getting started with own services!

Prerequisites:- Server: reasonably fast computer, fixed address in the network,Java 1.5 Runtime, Apache Tomcat - Client: any computer with Java runtimeInstall Server: Install Tomcat, open Tomcat manager in a browser(usually http://localhost:8080/manager), deploy the war-file availablefrom http://webgen.geo.uzh.chInstall JUMP Client: Install JUMP (http://www.jump-project.org),download the plug-in from http://webgen.geo.uzh.ch and place it in the extensions folderOpen JUMP, click on "WebGen06"->"WebGen List Services„ enterhttp://webgen.geo.unizh.ch/webgen/registry or if you have an own server e.g. http://localhost:8080/webgen/registry and click „view“ tosee all available services




Outlook and Discussion



Pros & Cons

ProInteroperability (hardware, software and programming language independent)Re-usability of developed generalisation functionalityBenchmarks and evaluation are easier (research)Application service providing and pay per use possible (industry)Chaining of different servicesExecution on specialised hardware (e.g. parallelisation)

ContraData transfer performanceComplexity (granularity of functional decomposition)Overhead (protocols, encoding, server processes)



Outlook

Further research– Interoperability issues

• Syntactic level (currently reached by WebGen or WPS)

• Semantic level Geo-Ontologies (data model semantic, service description semantics)

– Data transfer / architecture• Transfer and overhead –

bring the service (code) to the data?• Atomic vs. stateful services

– Parallelisation, grid computing Industry developments– ESRI ArcGIS Server– Axpand

More client plug-ins required for wider adoption



Conclusion

Increasing need and interest in the usage of service concepts for automated generalisationDifferent service approaches are proposed, showing the applicability of the service concept to generalisationWeb Services allow interoperable component based access and coupling of different platformsTwo service scenarios: Generalisation Middleware Service, Generalisation Toolbox ServiceService Categories: Support, Operator, ProcessResearch as well as industry developments of servicesPresentation of WebGen Service platform



Bibliography (1)Badard, T. & Braun, A. (2003). Oxygene: An open framework for the deployment of geographic web services. In Proceedings of the 21st International Cartographic Conference Durban, South Afrika.Burghardt, D., Neun, M., & Weibel, R. (2005). Generalization services on the web -– a classification and an initial prototype implementation. Cartography and Geographic Information Science, 32(4), 257–268.Edwardes, A., Burghardt, D., Bobzien, M., Harrie, L., Lehto, L., Reichenbacher, T., Sester, M., & Weibel, R. (2003). Map generalisation technology: Addressing the need for a common research platform. In Proceedings of the 21st International Cartographic Conference Durban, South Africa.Foerster, T. & Stoter, J. (2006). Establishing an ogc web processing service for generalization processes. In 9th ICA workshop on Generalisation and Multiple Representation Portland.Foerster, T., Stoter, J. & Lemmens, R. (2007).Towards automatic web-based generalisation processing: a case study. In 10th ICA/ACI Workshop on Generalisation and Multiple Representation Moskow, Russia.Goodchild, M.F. (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.Harrie, L. & Johansson, M. (2003). Real-time data generalisation and integration using java. Geoforum Perspektiv, (pp. 29–34).Harrie, L. (2005). Graphic generalisation methods in a system for real-time maps. In H. Hauska & H. T. (eds.) (Eds.), ScanGIS’2005 - Proceedings of the 10th Scandinavian Research Conference on Geographical Information Sciences.Harrower, M. & Bloch, M. (2006). Mapshaper.org: A map generalization web service. IEEE Computer Graphics and Applications, 26(4), 22–27.Lemmens, R., Wytzisk, A., de By, R., Granell, C., Gould, M., & van Oosterom, P. (2006). Integrating semantic and syntactic descriptions to chain geographic services. IEEE Internet Computing, 10(5), 42–52.



Bibliography (2)Lehto, L. & Kilpeläinen, T. (2000). Real-time generalisation of geodata in the web. Archives of Photogrammetry and Remote Sensing, XXXIII(Part B4), 559–566.Lehto, L. & Kilpeläinen, T. (2001). Generalizing xml-encoded spatial data on the web. In Proceedings of 20th International Cartographic Conference, volume 4 (pp. 2390–2396). Beijing.Neun M. and D. Burghardt (2005). Web Services for an Open Generalisation Research Platform. In Proceedings of the 8th ICA Workshop on Generalisation and Multiple Representation, A Coruña, Spain.Neun M., D. Burghardt and R. Weibel (2007, in press). Web Service Approaches for Providing Enriched Data Structures to Generalisation Operators. International Journal of Geographical Information Science.Regnauld, N. (2006). Improving efficiency for developing automatic generalisation solutions. In Joint ISPRS Workshop on Multiple Representation and Interoperability of Spatial Data Hannover.Regnauld, N. (2007). Evolving from automating existing map production systems to producing maps on demand automatically. In 10th ICA/ACI Workshop on Generalisation and Multiple Representation Moskow, Russia.Sarjakoski, T., Sester, M., Sarjakoski, L., Harrie, L., Hampe, M., Lehto, L., & Koivula, T. (2005). Web generalisation services in gimodig - towards a standardised service for real-time generalisation. In F. Toppen & M. Painho (Eds.), 8th AGILE Conference on GIScience Estoril, Portugal.Sester, M., Sarjakoski, L. T., Harrie, L., Hampe, M., Koivula, T., Sarjakoski, T., Lehto, L., Elias, B., Nivala, A.-M., & Stigmar, H. (2004). Real-time generalisation and multiple representation in the gimodig mobile service, gimodig-project, deliverables d7.1.1, d7.2.1 and d7.3.1. Public EC report, http://gimodig.fgi.fi/deliverables.php. (accessed 07/2006).



University of Zurich

Department of Geography

Dr. Dirk Burghardt and Moritz Neun

Tel.: +41 44 63 56534

[burg,neun]@geo.unizh.ch



Discussion issuesInteroperability issues– Syntactic level

(currently reached by WebGen or WPS)– Semantic level

(data model semantic, service description semantics)

Data transfer / architectureTransfer and overhead – bring the service (code) to the data?Atomic vs. stateful services



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