JPOX-Spatial and uDig Extending JPOX with Geospatial - HSR-Wiki

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JPOX-Spatial and uDig
Extending JPOX with Geospatial
Data Types and Functions
Management Summary of Diploma Thesis 2006/07 / Management Summary der Diplomarbeit im
Wintersemester 2006/07
Thomas Marti & Stefan Schmid
2007-01-05 [ManagementSummary_JPoxSpatial.doc].
Homesite auf http://wiki.hsr.ch/StefanKeller/wiki.cgi?JPoxSpatial
Industriepartners:
Refractions Research, Victoria, BC, Canada, www.refractions.net
Eisenhut Informatik AG, Burgdorf, www.eisenhutinformatik.ch
Supervisor / Betreuer:
Prof. Stefan F. Keller, Institut für Software und GISpunkt, www.ifs.hsr.ch
1 Introduction
A large partition of business information refers in some way to a location. This spatial
component often matters. As an increasing number of today's relational database management
systems (RDBMS) provide an infrastructure to support both enterprise GIS and business
requirements, location based information becomes an integral part of mainstream IT.
Consequently the last decade has seen a significant rise of geographic information systems
(GIS).
Java has become a programming language of choice for GIS and spatially related applications.
Developers of a Java application housing their data in a RDBMS have to bridge the gap
between the relational world and the object-oriented world. The task of persisting Java objects
to a relational database is currently being facilitated by a number of different object-persistence
technologies.
Diploma Thesis / Diplomarbeit JPOX-Spatial and uDig
Sun's JDO specification provides a technology for transparently persisting Java objects
(POJOs). This standardized, object-oriented persistence API promises high usability and
performance. For practical reasons the specification only demands mandatory support for a
very limited set of basic Java types, because a persistence solution can never know how to
persist all possible types. Because of this, support for spatial data types in current JDO
implementations is sparse. Additionally one of the most important requirements of GIS
applications are spatial functions like bounding box queries or complex geographic relations,
which in many cases have to be calculated for massive amounts of data. It is therefore
imperative to execute such queries on the database side and not in memory on Java objects.
JPOX is an open source and fully compliant JDO implementation that was chosen by Sun as
reference implementation for the JDO 2.0 specification. It supports a great number of RDBMSs
on the market today and is maintained by very enthusiastic core developers. The code base is
uncluttered and well-refactored.
Overview of the architecture / Architektur-Übersicht
2 Vision
Our vision is to provide industry standard persistence for any geospatial application. We want to
provide a plug-and-play approach with the application's geometry object model as well as with
the underlying RDBMS. This means users should be able to easily replace the RDBMS and/or
the geometry library as long as they are compliant to the Open Geospatial Consortium Simple
Features specification (OGC SFS). OGC is an industry standard body organisation acting
worldwide.
3 Goals
The goal of JPOX-Spatial was to allow the use of JPOX as a persistence layer for geospatial
applications. To achieve this we had to extend several parts of JPOX:
Institut für Software www.ifs.hsr.ch / GISpunkt www.gis.hsr.ch
2
Diploma Thesis / Diplomarbeit JPOX-Spatial and uDig
• Define type mappings to let JPOX know how to persist spatial Java types.
• Extend the query language with spatial functions according to the OGC SFS specification.
• Adapt JPOX for the specifics of spatial databases.
The vast majority of current open source GIS projects in the Java world use the so called JTS
Topology Suite as basis for geometry representation. On the backend side, PostGIS has
become the standard spatial database for open source GIS tools. PostGIS adds spatial
database capabilities to PostgreSQL. On this account, support for JTS and PostGIS is a musthave to meet the requirements of the open source community. In commercial environments the
use of Oracle, IBM DB2 and other RDBMSs is widespread. Support of most of these RDBMSs
needs to be implemented too.
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Results
JPOX-Spatial was successfully integrated in the GIS-framework uDig. Currently following
RDBMSs are supported: PostgreSQL, MySQL, Oracle and IBM DB2.
JPOX-Spatial was compared to JDBC and showed satisfactory performance: It loads for
example geospatial objects with 10 Mio. geometry points.
JPOX-Spatial has been chosen to be the official spatial extension for JPOX which means that
several unit tests have been implemented and passed. The spatial extension is defined as an
Eclipse plugin and therefore conforms to the OSGi format. It makes use of several extension
points of the JPOX core and provides all the functionality that are vital for Jave developer
programming a spatially enabled business application.
More info:
• JPOX-Spatial project information page: http://wiki.hsr.ch/StefanKeller/wiki.cgi?JPoxSpatial
• JPOX: http://www.jpox.org/docs/1_2/whats_new.html ("What's New in 1.2...”).
Visualization of hospital locations in the area of Vancouver Island / Visualisierung von SpitalStandorten in der Gegend von Vancouver Island
Institut für Software www.ifs.hsr.ch / GISpunkt www.gis.hsr.ch
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Diploma Thesis / Diplomarbeit JPOX-Spatial and uDig
Managment Summary (deutsch)
1 Aufgabenstellung
Wer bei Geographischen Informationssystemen (GIS) nur an digitale Landkarten oder GPSNavigation im Auto denkt, liegt falsch! Schätzungen zufolge haben bis zu 80% aller
Geschäftsdaten einen räumlichen Bezug. Eine zunehmende Anzahl von Datenbankherstellern
hat dies erkannt und ihre Produkte um räumliche Datentypen wie Punkt oder Fläche erweitert.
Applikations-Programmierer in einem typischen Business-Umfeld können für die nicht-triviale
Aufgabe, Java-Objekte in relationalen Datenbanken zu speichern, auf komfortable
Persistenzframeworks, wie zum Beispiel JPOX zurückgreifen. Raumbezogene Datentypen und
Funktionen werden dabei aber noch nicht im gewünschten Umfang unterstützt. In dieser
Diplomarbeit soll deshalb JPOX so erweitert werden, dass über die standardisierte JDOSchnittstelle gleichermassen auf räumliche wie auf 'normale' Daten zugegriffen werden kann.
2 Ziel der Arbeit
Das in der vorangegangenen Studienarbeit erstellte Plugin soll verbessert, erweitert und ins
offizielle JPOX-Projekt integriert werden. Dazu wird der gesamte Code an dessen
Projektumgebung angepasst und schliesslich dem Open-Source-Projekt übergeben. Die
Praxistauglichkeit von JPOX-Spatial soll anhand der Integration in GeoTools und uDig (Userfriendly Desktop Internet GIS) demonstriert werden. Um Stabilität und Performanz auch bei
grossen Datenmengen sicherzustellen, werden umfangreiche Lasttests durchgeführt.
3 Lösung
Die Arbeit wurde als offizielles JPOX-Plugin aufgenommen und wird ab Version 1.2 zum
Standard-Umfang gehören. Bei der graphischen Darstellung von öffentlich verfügbaren
Musterdaten in uDig (Bild links) konnte sich JPOX-Spatial im ersten praktischen Einsatz
bewähren. Die auf einem gewöhnlichen Laptop durchgeführten Lasttests haben zudem
bewiesen, dass auch riesige Datenmengen wie Polygone mit 10 Millionen Punkten noch zügig
gespeichert werden.
Weitere Infos: www.jpox.org/docs/1_2/spatial.html
Institut für Software www.ifs.hsr.ch / GISpunkt www.gis.hsr.ch
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