High quality presentation of geo-data as a result of system independent conceptual modeling with INTERLIS

Hans Rudolf Gnägi, Andreas Morf

IGP-ETHZ

1. Introduction

The recently held OEEPE meeting of European mapping authorities showed a noticeable need for solutions with regard to following aspects:

· High quality map presentation on the internet is nowadays a vital prerequisite for a successful (web) presence of data producers and sellers.

· The complexity of XML/GML and associated technology and software-tools is growing every month. Therefore a substantial need for easy to use and flexible standards like INTERLIS (data modeling, transfer) and SVG (presentation) is obvious.

· Importance of system independent modeling of geodata which facilitates the creation of transformation patterns. Among other representations of a geo-dataset SVG is well suited to achieve outstanding semi-interactive cartographic map presentations.

In the following chapters we want to give an overview of the phases from an exact conceptual model to the (carto-) graphic presentation. Finally some conclusions and restrictions of the currently used technology will be presented.

2. Data modeling provides a consistent workflow

A short presentation of the techniques used for the conceptual modeling of spatial data will provide the audience with the necessary information to understand the following phases of the workflow. UML as a visual language for creating a data model can be used as a starting point. The description of the conceptual model with the INTERLIS language is generated automatically out of the UML diagram. Finally the specification of INTERLIS allows the automatic deduction of an XML based data format which is the key for introducing the SVG presentation layer.

3. Symbology modeling leads to system independent graphical presentation

The INTERLIS mechanism not only provides the possibility to model geodata, it also introduces the possibility to model the associated symbologies absolutely independent from the data. Therefore libraries for different visualization purposes can be easily developed.

4. Concept of the link between data and symbologies

Within the concept of the INTERLIS mechanism the two independent models are linked to each other via graphic-definition: based upon a class or view, for every object a signature out of the attached symbol library is assigned.

5. Presentation of the developed INTERLIS to SVG-Translator

Based upon freely available tools from the 'Apache XML Project' a prototype of an INTERLIS-SVG translator was developed. The intensive use of XSL Transformations is the pivotal point. Details and problems will be presented in the full paper version.

Some visual results will be presented at the conference.

Possibly: Comparison of the different concepts of ETHZ and HSR)

6. Handling of large datasets

As a matter of fact many of the actually used geo-datasets are quite large and hard to transfer over the net and to handle with contemporary SVG viewers. The properties of INTERLIS with regard to interoperability between GIS allows us to implement our solution as a service of these systems which are capable to handle INTERLIS. As a result the power of these systems in the field of spatial and thematic selection (among other) can be fully profited of. Especially the deployment of internet services as front-ends to GI-Systems (web map service) are of interest (cf. GeoShop).

7. Advantages

A conceptual approach provides system independence. Our conceptual approach also allows the development of patterns and tools which may be applied to entire subject areas. A link between data and independently defined symbologies allows the graphical presentation of different thematic aspects and as well, to certain extent, of different scales for the same data.

8. Problems and solutions

Restricted browser or viewer capacity or network bandwidth:

• Need for selection possibility (Ch. 6)

Limitation in the current SVG specification:

• The potential of a conceptual approach lets us easily switch to an other visualization format or tool for special purposes. This can be achieved with available conversion-software (ICS: Interlis Conversion System, FME, XSLT (cf. GML, X3D, VRML)