p might allow p to appear in a term of the form f(p), but disallow it to occur in a term like p(a,b). The signature for f, on the other hand, might allow that symbol to appear in f(p) and f(p,q), but disallow f(p,q,r) and f(f). In this way, it is possible to control which symbols are used for predicates and which for functions, where variables can occur, and so on.
A beneficial dialect you’ll impose subsequent constraints toward style of an effective style of variety of title or formula. Such as for instance, variables otherwise aggregate conditions might not be greet in a number of metropolises.
Semantic structure. This framework defines the notion of a great semantic construction (known as interpretation on the literary works [Enderton01, Mendelson97]). Semantic structures are widely used to interpret algorithms and also to establish logical entailment. As with the fresh new sentence structure, this framework includes lots of components you to RIF reasoning dialects can be specialize to complement their requirements. These types of components tend to be:
For every single RIF dialect which is produced by RIF-FLD is described in individual file
- Group of knowledge thinking. RIF-FLD was created to match dialects that assistance reason which have contradictory and you can unsure information. All of the logics that are designed to handle these types of situations is multi-valued. For that reason, RIF-FLD postulates there is some facts thinking, Television, which includes the values t (true) and you can f (false) and perhaps anyone else. For example, this new RIF Very first Logic Dialect [RIF-BLD] is actually a few-valued, but almost every other languages may have extra specifics viewpoints.
- Semantic formations. Semantic structures determine how the various icons on alphabet off an effective dialect was interpreted as well as how details beliefs is assigned to formulas.
- Datatypes. Some symbol spaces that are part of the RIF syntactic framework have fixed
interpretations. For instance, symbols in the symbol space are always interpreted as sequences of Unicode characters, and a ? b for any pair of distinct symbols. A symbol space whose symbols have a fixed interpretation in any semantic structure is called a datatype. - Entailment. This notion is fundamental to logic-based dialects. Given a set of formulas (e.g., facts and rules) G, entailment determines which other formulas necessarily follow from G. Entailment is the main mechanism underlying query answering in Databases, Logic Programming, and the various reasoning tasks in Description Logics.
A set of formulas G logically entails another formula g if for every semantic structure I in some set S, if G is true in I then g is also true in I. Almost all logics define entailment this way. The difference lies in which set S they use. For instance, logics that are based on the classical first-order predicate calculus, such as most Description Logics, assume that S is the set of all semantic structures. In contrast, most Logic Programming languages use default negation. Accordingly, the set S contains only the so-called minimal Herbrand models [Lloyd87] of G and, furthermore, only the minimal models of a special kind. See [Shoham87] for a more detailed exposition of this subject.
XML serialization construction. It construction describes the overall values getting mapping the new speech sentence structure off RIF-FLD with the tangible XML interchange style. Including:
For each RIF dialect which is derived from RIF-FLD might possibly be demonstrated in own document
- A requirements of the XML sentence structure to own RIF-FLD, like the associated XML Schema file.
- A specification out of a one-to-you to definitely mapping from the presentation syntax regarding RIF-FLD so you can the XML sentence structure. So it mapping must map one well-molded formula off RIF-FLD to an XML such as for instance document that’s appropriate in respect with the aforementioned XML Outline file.
Which specs is the newest write of the RIF-FLD definition. The initial eg dialect, new RIF Very first Reasoning Dialect, is explained in the [RIF-BLD]. A core dialect, which is discussed because of the next concentrating RIF-BLD, try given from inside the [RIF-Core].