5.3.5.2. Graph transformation rules

The realization of the model transformation process is mainly based on the concept of “Graph transformation” and implemented using the open source graph transformation engine Attributed Graph Grammar (AGG). The AGG transformation tool comes with a graphical editor that allows users to define an arbitrary number of graph-structured transformation rules for mapping complex object-oriented models onto a compact relational database models. The graph transformation process implemented for the ADE Manager plugin as well as the most relevant transformation rules are discussed in detail in [YaKo2017].

While developing the ADE Manager plugin, around 50 default mapping rules have been defined and tested. Using these predefined mapping rules, well-known CityGML ADEs like the Energy ADE, i-UR ADE, Noise ADE, UtilityNetwork ADE, Dynamizer ADE, IMGeo3D ADE and further custom ADEs could be successfully and correctly transformed to compact relational schemas for the 3DCityDB. Thus, typically, there is no need for users to change or customize the default rules used by the transformation operation.

If you nevertheless want to modify these default rules or even add your own additional rules, you have to build a customized version of the ADE Manager plugin. For this purpose, clone the source code of the ADE Manager plugin from its GitHub repository at https://github.com/3dcitydb/plugin-ade-manager to a folder in your local file system.

The graphical editor of the AGG tool can be started with the runnable JAR file AggV21Build.jar that can be found in the lib subfolder of the cloned repository. On most systems, double-clicking this JAR file will launch the AGG editor. If this does not work for you, you can execute the AGG editor from the command line with the following command.

$ java -jar AggV21Build.jar

Once the AGG tool has started, use File -> Open from the main menu bar of the user interface to load the default transformation rules that are used by the ADE Manager plugin. The AGG workspace file you have to load is called Working_Graph.ggx and is located in the subfolder src/main/resources/org/citydb/plugins/ade_manager/graph. Modify this file and the contained rules according to your needs.

Fig. 5.24 AGG graph editor for defining model transformation rules for the ADE Manager plugin.

When you have completed the work with the AGG editor, you have to compile your customized version of the ADE Manager plugin. The plugin uses Gradle as build system. To build the plugin from source, open a terminal on your local machine and change to the folder where you have cloned the repository of the plugin. Afterwards, run the following command in this folder.

$ gradlew installDist

The script automatically downloads all required dependencies for building the ADE Manager plugin. So make sure you are connected to the internet. The build process runs on all major operating systems and only requires a Java 8 JDK or higher to run. The build process will produce the plugin software package under build/install. Simply copy the contents of this folder into the plugins folder of your Importer/Exporter installation to use the plugin.