Question: UML does not support DFDs because DFDs do not fit as cleanly into a consistent object-oriented paradigm.

Answer: UML does not support DFDs because DFDs do not fit as cleanly into a consistent object-oriented (OO) programming paradigm. Object-oriented programming (OOP) is a programming language model organized around object rather than "actions" and data rather than logic. Historically, a program has been viewed as a logical procedure that takes input data, processes it, and produces output data. However, in object oriented programming, the data structure become an object that includes both data and function and it also create relationships between one object and another. It is defined not only the data type of a data structure, but also the types of operation ( function) that can be applied to the data structure. As we also know A DFD is a graphical representation of how the data flows within a system, while UML is a modeling language used in object oriented software design. Activity diagrams accomplish much of what people want from DFDs and then some; activity diagrams also are useful for modeling work flow.