Recently I need to create a UML diagram based on some domain models and I found a text based one called PlantText. In this you can write code to generate UML diagram. The main point of interest is you can store and manage your UML generation code in your source control the same way of your application code. You can re-generate the UML diagram from the code at any time from the PlantText website. Not just UML diagram they have many other kinds of diagram support as well.

https://www.planttext.com/

@startuml

abstract class Car {
  +int Id
  +string Name
  +void Start()
  +void Accelerate()
  +void DeAccelerate()
  +void Stop()
}

class BMW {
  +float Price
  +Location GetGpsLocation()
  +Warranty GetWarranty()
}

Car <|-down- BMW

@enduml