1. Early query language, ca. 1965, System Development Corp, Santa Monica, CA. [Sammet 1969, p.701].

2. A family of dataflow languages descended from ISWIM, lazy but first-order.

Ashcroft & Wadge <>, 1981.

They use a dynamic demand driven model. Statements are regarded as equations defining a network of processors and communication lines, through which the data flows. Every data object is thought of as an infinite stream of simple values, every function as a filter. Lucid has no data constructors such as arrays or records. Iteration is simulated with 'is current' and 'fby' (concatenation of sequences). Higher-order functions are implemented using pure dataflow and no closures or heaps.

["Lucid: The Dataflow Language" by Bill Wadge <wwadge@csr.UVic.CA> and Ed Ashcroft, c. 1985]. ["Lucid, the Dataflow Programming Language", W. Wadge, Academic Press 1985].