Initially, diagrams descriptions have to start with @startuml and to finish with @enduml. PlantUML allows now to generate other diagrams than UML, and in that cases, @startuml would not make sense anymore.
So, the general convention is to let diagrams descriptions start with @startXYZ and to finish with @endXYZ, where XYZ has to be changed with the type of diagrams.
Note that XYZ could be any strings of characters (including spaces).
This means that plugin developers are encouraged to change their code to recognize @start instead of @startuml.
Ditaa is an Open Source project that allows to generate general diagrams from a text descriptions. The idea is close to PlantUML, and it may be useful for documentation to generate other diagrams than UML.
So last version of PlantUML allows this :
You will find here the complete documentation about this.
If your plugin does not support @startditaa yet, a temporary feature has been set up : it is also possible to use Ditaa with @startuml by using ditaa keyword on the very first line of your description.
You can also use some option, after the @startditaa or @ditaa keyword: