The example you are using as reference is [creating custom functions with annotations](https://community.denodo.com/docs/html/browse/6.0/vdp/developer/developing_extensions/developing_custom_functions/creating_custom_functions_with_annotations), so the name of the class is not relevant in this case. This is the way I strongly recommend to develop custom functions.
However, you can as well [create custom functions using name conventions](https://community.denodo.com/docs/html/browse/6.0/vdp/developer/developing_extensions/developing_custom_functions/creating_custom_functions_using_name_conventions) so here you should take into account the class name. As you can see in the previous link, in this case the name of the class should follow two rules:
* **<FunctionName>VdpFunction** for condition functions
* **<FunctionName>VdpAggregateFunction** for aggregation functions
Hope this helps!