WebGIS application with OpenLayers 2 - Part 3: Data management

In the last part of the series, we will cover data management in OpenLayers 2. It is a quite difficult part, as browsers mostly don't have native support for relational databases. The only exceptions are browsers powered by WebKit. This way, we have to make sure manually, that our data is stored in a consistent way. ASCII geodata formats, which are mainly used in web mapping environments don't support databases. We can store different attributes for every geometry in a layer/dataset. This doesn't seem to be an issue on the first glance, as web mapping libraries can handle object-oriented databases very well. However, if you declare attributes arbitrary, in an inconsistent way, you will have a hard time when you try to process it with a RDBMS. As the server side processing GIS softwares (e.g. QGIS, GRASS, PostGIS) will put these datasets into a relational database, it might be a wise consideration to handle features like they were in a relational table on the frontend.

Map server basics

If you would like to build your own map server, you have to think it through carefully first. Do you need a complete map server or you can stack with an existing one? Is Google Maps good for you or you need more control on your maps? There are several options on the internet and with some of them, you just have to write a brief JavaScript code and voilà, you have a well-visualized map. In the next few articles I will show some options which won't need an independent map server, but learning at least one of them will be inevitable if you have to build one.