Distributed GML Management With SVG Tools

- Extended Abstract -

Gunnar Misund gunnar.misund@hiof.no
Henning Kristiansen henning.kristiansen@hiof.no
Mats Lindh mats.s.lindh@hiof.no
Ostfold University College, Halden, Norway

Abstract

We present a browser based GML editor implemented with SVG and DOM scripting. The editor is a able to treat GML 2 compliant data. The geometric editing is based on moving, deleting and inserting points and groups of points, thus treating the basic simple feature geometry properly. Thematic properties are edited in tables. The editor is designed, within certain limits, to be a multi purpose editor. However, the main target application is data management in Project OneMap (1). The main objective of this project is to incrementally build a large, distributed global online map.

Project OneMap

In order to clarify the main reasons for implementing the GML editor, we give a brief outline of Project OneMap, which is the main target application. OneMap is functionally comprised by three main components: Repository, Gateway and Clearinghouse. The alpha version has been up and running for a year, and the beta version will be released in June this year.

Repository

The repository is a distributed storage infrastructure. This is basically a (huge) set of GML files structured to efficiently support retrieval and updating of the geodata comprising the world map. The total amount of base data is currently in the magnitude of 50 M points, and is expected to expand to around 500 M points within the next few months. The data is structured in levels of detail to facilitate global overviews as well as street level inspections. The files are distributed redundantly on a set of servers. This facilitates both storage scalability and parallell processing of retrieval queries and updating procedures.

Currently we use a straight forward directory based management of the distributed data. However, work is in progress to implement a P2P infrastructure to avoid bottlenecks and single-points-of-failure.

The communication within the OneMap infrastructure is based on Web Services paradigms and technology. The main interface to the repository is realized as a OGC Web Feature Server (currently non transactional).

Gateway

The Gateway is a browser based user interface for retrieval of OneMap data. We are using an SVG/javascript implementation, which provides simple but sufficient navigation and query possibilities. In addition to the SVG view, the users may download the GML version of the response.

Clearinghouse

One of the main objectives of OneMap is to make it possible to build a huge map in an incremental and uncoordinated manner, with contributions from a wide variety of parties, but still maintain a reasonable level of reliability and quality.

The main problem is to integrate submissions with the existing geodata. We address the problem by using a framework based on the well known principles of peer review. The process of contributing new geodata or updates of existing data is outlined as follows:

Work is in progress to interface the clearing house processes to the Repository as a transactional OGC Web Feature Server.

The GML Editor

There are currently three main tools interfacing the OneMap repository with the users, the Gateway UI, the Submission UI and the GML editor, all SVG based. In the paper we will focus on the editor.

The core tool in the geodata clearing process is the GML editor. The editor is a browser based SVG/script client application. The editor communicates with the OneMap server by receiving integration maps and uploading edited versions. The editor is supporting collaboration within the peer group. However, the main functionality is to edit both the geometric and thematic content of GML files.

The editor is designed to treat arbitrary GML 2 compliant data sets. In addition, it will handle files enhanced with integration information, e.g. topological violations. The main bulk of the functionality is implemented in the current prototype.

References

  1. Gunnar Misund and Knut-Erik Johnsen: The One Map Project. In online proceedings from GML Dev Days, Vancouver, July 2002.