Question: Why does DynamicSystems recognise an AlgebraicEquation as a Differential Equation?

hi,

I am trying to make a custom on maple but when i get an error on dynamicSystems saying:

> sys := DynamicSystems[AlgEquation](eq, inputvariable = [Altura(t)], outputvariable = [Teste(t)]);
Error, (in DynamicSystems:-AlgEquation) algebraic equations cannot depend on past/future values of the input/output

But if i change AlgEquation to diffEquation i get no error. I dont have any diff equation on the system. This is happening with one of the "equations":

Does anybody knows why?

Thanks