Linda [] is a concurrent programming model that has evolved from a Yale University research project. The primary concept in Linda is that of a ``tuple-space'' , an abstraction via which cooperating processes communicate. This central theme of Linda has been proposed as an alternative paradigm to the two traditional methods of parallel processing: that based on shared memory, and that based on message passing. The tuple-space concept is essentially an abstraction of distributed shared memory, with one important difference (tuple-spaces are associative), and several minor distinctions (destructive and nondestructive reads and different coherency semantics are possible). Applications use the Linda model by embedding explicitly, within cooperating sequential programs, constructs that manipulate (insert/retrieve tuples) the tuple space.
From the application point of view Linda is a set of programming language extensions for facilitating parallel programming. It provides a shared-memory abstraction for process communication without requiring the underlying hardware to physically share memory.
The Linda system usually refers to a specific implementation of software that supports the Linda programming model. System software is provided that establishes and maintains tuple spaces and is used in conjunction with libraries that appropriately interpret and execute Linda primitives. Depending on the environment (shared-memory multiprocessors, message-passing parallel computers, networks of workstations, etc.), the tuple space mechanism is implemented using different techniques and with varying degrees of efficiency. Recently, a new system scheme has been proposed, at least nominally related to the Linda project. This scheme, termed ``Pirhana'' [], proposes a proactive approach to concurrent computing: computational resources (viewed as active agents) seize computational tasks from a well-known location based on availability and suitability. This scheme may be implemented on multiple platforms and manifested as a ``Pirhana system'' or ``Linda-Pirhana system.''