The Free On-line Dictionary of Computing (30 December 2018):
data flow
A data flow architecture or language performs a
computation when all the operands are available. Data flow is
one kind of data driven architecture, the other is demand
driven. It is a technique for specifying fine-grain
concurrency, usually in the form of two-dimensional graphs in
which instructions that are available for concurrent execution are
written alongside each other while those that must be executed in
sequence are written one under the other. Data dependencies
between instructions are indicated by directed arcs. Instructions
do not reference memory since the data dependence arcs allow data
to be transmitted directly from the producing instruction to the
consuming one.
Data flow schemes differ chiefly in the way that they handle
re-entrant code. Static schemes disallow it, dynamic
schemes use either "code copying" or "tagging" at every point
of reentry.
An example of a data flow architecture is MIT's VAL
machine.