Set-based languages have emerged as a powerful means for expressing not only programs but also requirements, test cases and so on. However, a uniform compilation schema for sets has not yet been completely developed. The present paper tries to overcome this lack using a set-based logic language, SL (set language), as target. The approach is based on an imperative abstract machine, the SAM (set abstract machine). The translation from SL to SAL (SAM assembly language) is described and all the possible optimizations, both at source code level and at assembly code level, are detailed. The potentials for identifying parallel flows of computations are analysed. Several examples of compilations are presented and discussed.

Subset-equational programming is a paradigm of programming with subset and equality assertions. The underlying computational model is based on innermost reduction of expressions and restricted associative-commutative (a-c) matching for iteration over setvalued terms, where [ is the a-c constructor. Subset assertions incorporate a `collect-all' capability, so that the different subset assertions matching a goal expression and the different a-c matches with each subset assertion are all considered in defining the resulting set of the goal expression. We provide several examples to illustrate the paradigm, and also describe extensions to improve programming convenience: negation by failure, relative sets, and quantifiers. We also discuss the use of subset-equational programming for intelligent decision systems: the rule-based notation is well-suited for expressing domain knowledge and rules; subset assertions are especially appropriate in backchaining systems like MYCIN, which performs an...

Logic programming is generally taken to be synonymous with relational programming; however, this paper argues why a broader basis for logic programming is needed, why existing combinations of equations, relations, and functions do not entirely meet the need, and a promising approach for the broader basis. The proposed broader basis consists of three logical forms: equations, relations, and subset assertions, along with an accompanying set of matching and unification operations. Equations provide the ability to define deterministic operations without Prolog's cut. Subset assertions can be used to define more declaratively Prolog's setof as well as transitive-closure operations, both of which are traditionally expressed using assert and retract. Because functions defined by subset assertions must be invoked with ground arguments, formulating relational clauses by subset assertions allows one to declaratively specify which arguments of a relation are ground, thereby obviating the need for...

Abstract: Nowadays, information plays a fundamental role inside every kind of activity: its ever-growing importance does not regard only computer science but also concerns a huge number of everyday activities. Information is useful only if it is structured and manageable: this is perhaps the main goal of all the information systems. This paper describes an original alternative to the same old graphical forms used to query a repository: a set based logic query language. The query technique proposed is based on a declarative language that emphasises the set as main data type. In particular, sets are a natural and intuitive model for structured data collections. The query language produced, called SubSet Query Language (SSQL), expands the functionalities of the starting language and introduces the capability to access an external repository. A class of new built-in predicates has been added to the starting language and the compilation and the execution environment have been adapted to the new functionalities introduced. The SSQL paradigm has been integrated inside a distributed software artefact library and use statistics are being gathered. An initial evaluation of the SSQL paradigm, based on the experience so far acquired, shows that, in the phase of an initial effort to experience the