Enum Term 

pub enum Term {
    Variable(VariableSymbol),
    Constant(ConstantSymbol),
    TripleTerm(Box<Atom>),
    Skolem {
        name: ConstantSymbol,
        args: Vec<Term>,
    },
}

Datalog term (variable, constant, quoted-triple term, or SKOLEM(name, args...) function call).

The TripleTerm variant lets rules name quoted-triple arguments per RDF 1.2 / RDF-star, encoded as a 2-arity Atom whose predicate is the triple’s predicate IRI and whose terms slot holds [subject, object]. Nesting is bounded by MAX_TRIPLE_TERM_NESTING to keep unification cost finite — programs that exceed the limit are rejected at Program::validate time.

The Skolem variant (extension) is a deterministic fresh-IRI minting operator: given a label and a tuple of argument terms, the evaluator produces a stable urn:example:skolem:<label>:<hash> IRI that’s content-addressed from the argument bindings. SKOLEM is only meaningful in head positions — body atoms that carry a Skolem term are rejected at validation time as super::error::ProgramValidationError::SkolemInBodyAtom because a SKOLEM term has no pattern semantics (it’s a function, not a wildcard).

Variants

Variable(VariableSymbol)

Variable term.

Constant(ConstantSymbol)

Constant term.

TripleTerm(Box<Atom>)

Quoted-triple term: an inner Atom used as a value in the enclosing atom. Conceptually represents << s p o >> per RDF 1.2 N-Triples-star syntax.

Skolem

SKOLEM(name, arg_1, …, arg_n) — a deterministic fresh-IRI minting function (extension). Permitted in rule heads only; arguments must be Self::Variable or Self::Constant (no nested SKOLEM, no quoted-triple terms).

Fields

name: ConstantSymbol

Label that namespaces the skolemized IRI — typically a short ASCII tag like "example-key" so collisions across independent rule sets stay scoped per author.

args: Vec<Term>

Argument terms whose ground values feed the content-addressed hash. Must be variables or constants.

Implementations

impl Term

pub fn is_skolem(&self) -> bool

Returns true when the term is a SKOLEM(...) function call. Used by body-atom validation to reject SKOLEM terms outside head positions.

Trait Implementations

impl Clone for Term

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Term

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for Term

Display a Term: variables as ?<name>, constants as their raw symbol, and triple terms as << s p o >> per N-Triples-star syntax.

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for Term

impl Hash for Term

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for Term

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Term