How to represent OOP concepts in algorithms in a standard way?
Generally there is no unified to present algorithms. Each researcher should use/introduce notation with which he is most comfortable with.

If you look at some algorithmic books writers have different approach to this manner.

For instance:


CLRS book gives no types for functions arguments
Tel's "Introduction to distributed algorithms" gives types
Sedgewick's "Algorithms" gives code in Java (which is not very good solution IMO)


On the other hand any object can be represented as tuple of base data types, eg binary tree can be presented as:

(5,(3,(1,NIL,NIL),(4,NIL,NIL)),(6, NIL, NIL))


Which might corresponds to

5
|\
3 6
|\
1 4


But the first notation is not very readable, so its easier to relate so such tuple as Node.

Additionally algorithms representation depends on field on which they are presented. If you assume that algorithm should be more or less translatable from pseudo code to actual code then you should introduce hints and notation to your algorithm presentation which allow this. But if that is not the case and you want to focus mainly on algorithm idea, or some other complexity value then, time then mathematical notation might become handy. In the end as previously stated it depends on needs.

If you look closely on various papers and books you can see that types of arguments are either obvious from context, or explained in algorithm description.

I suggest you to get familiar with $\LaTeX$ Algorithms module.