A Scalable Distributed Multimedia Knowledge Retrieval System on a Cluster of Heterogeneous High Performance Architectures

instructions Control stack Program Data parallel environment communication association Fig. 2. A heterogeneous associative model. represented as an associative frame, and uses associative vectors to facilitate fast backtracking. The vectors are indexed with respect to the base of the current frame. Variable aliases are indicated by filter vectors and are tracked by the alias management table. The logical OR of two vectors creates the union of two sets of aliased variables when members of the two sets are aliased by an instruction. A detailed explanation of this model and the corresponding abstract instructions is given in [4]. A shared variable has two occurrences in a clause body: a producer occurrence and a consumer occurrence. The producer occurrence generates a value for the shared variable, and the consumer occurrence uses the value of a variable. 2.2. Notations for the abstract instructions In this section, we define the notations used in the examples. We will show examples of the abstract instructions code for both the abstract machine of the server processes and the distributed abstract machine used by the coordinator. A symbol denotes the start of a procedure with an arity of . A symbol _CN denotes the start of the Nth clause of the predicate . A symbol denotes a universal filter vector a vector of Boolean values associated with a set of clauses to identify unifiable clauses. A symbol denotes a binding filter vector a vector of Boolean values marking the values in the clause-head representation to which a variable in a goal will be bound after unification. A symbol denotes a fact vector a vector of Boolean values marking the facts in a knowledge base. A symbol denotes a clause filter vector a vector of Boolean values marking clauses with non-empty body. A symbol denotes the Nth argument of the current goal. A symbol denotes a temporary Boolean Filter vector. A symbol indicates a global register, and a symbol denotes a variable. A symbol indicates a Boolean filter vector marking the servers which contain a particular predicate, and a symbol denotes a label. Example 1 illustrates a simple logic program. The corresponding compiled abstract instruction code is given in Figure Stephen W. Ryan and Arvind K. Bansal