Papers

T Spaces: The Next Wave (1999)

Summary. T Spaces is a

tuplespace-based network communication buffer with database capabilities that enables communication between applications and devices in a network of heterogeneous computers and operating systems

Essentially, it's Linda++; it implements a Linda tuplespace with a couple new operators and transactions.

The paper begins with a history of related tuplespace based work. The notion of a shared collaborative space originated from AI blackboard systems popular in the 1970's, the most famous of which was the Hearsay-II system. Later, the Stony Brook microcomputer Network (SBN), a cluster organized in a torus topology, was developed at Stony Brook, and Linda was invented to program it. Over time, the domain in which tuplespaces were popular shifted from parallel programming to distributed programming, and a huge number of Linda-like systems were implemented.

T Spaces is the marriage of tuplespaces, databases, and Java.

• Tuplespaces provide a flexible communication model;
• databases provide stability, durability, and advanced querying; and
• Java provides portability and flexibility.

T Spaces implements a Linda tuplespace with a few improvements:

• In addition to the traditional Read, Write, Take, WaitToRead, and WaitToTake operators, T Spaces also introduces a Scan/ConsumingScan operator to read/take all tuples matched by a query and a Rhonda operator to exchange tuples between processes.
• Users can also dynamically register new operators, the implementation of which takes of advantage of Java.
• Fields of tuples are indexed by name, and tuples can be queried by named value. For example, the query (foo = 8) returns all tuples (of any type) with a field foo equal to 8. These indexes are similar to the inversions implemented in Phase 0 of System R.
• Range queries are supported.
• To avoid storing large values inside of tuples, files URLs can instead be stored, and T Spaces transparently handles locating and transferring the file contents.
• T Spaces implements a group based ACL form of authorization.
• T Spaces supports transactions.

To evaluate the expressiveness and performance of T Spaces, the authors implement a collaborative web-crawling application, a web-search information delivery system, and a universal information appliance.