Hash Table

WikiWikiWeb:HashTable - A Hash Table is a Data Structure for storing Key-Value pairs; that is, an implementation of the DictionaryData Structure. Hash tables can be startlingly efficient...

how does this relate to a TupleSpace?

In many situations, hash tables turn out to be more efficient than search trees or any other table lookup structure. For this reason, they are widely used in many kinds of computer software, particularly for Associative Array-s, database indexing, caches, and sets. http://en.wikipedia.org/wiki/Hash_table