Next: Feature Terms
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In this glossary, terms appearing in boldface indicate they are defined in the
glossary. We will use term as a shorthand for feature term.
- Anonymous terms --
- A term that has no identifier, it can be
referenced only by its position (as a subterm of other terms). For
instance in (define (person Jack) (girlfriend (define (girl))))
the girlfriend of Jack is anonymous and can only be referenced by
(>> girlfriend of Jack).
- Any --
- The highest constituent in the refinement hierarchy for
constant terms. Definitions that elide naming a constituent
are constructed as a refinement of any. So (define foo) is
just a short syntax from (define (any foo)).
- Constant term --
- A feature term that is not a method-i.e. is
- Constituent --
- The constituent of a term is the identifier of
that from which it has been constructed by refinement.
- Description --
- The syntax for constructing feature terms.
The textual representation (define A (X (define (Y))) ...)
that constructs the corresponding feature term. The outmost
define is called root (A in the example). Relative path
references appearing in the description are relative to the root.
- Ephemeral term --
- A term that is not memorized--and thus is not
amenable to retrieval.
- Equality constraints --
- Path equality in feature terms is
equivalent variable binding. See
- Failure --
- When a global failure occurs, the token fail is returned
This occurs when no value can be inferred that satisfies any set of
equality constraints. In a specific subtask, a failure occurs when no
value can be inferred that satisfies the current equality constraints
--and causes backtracking at that point.
- Feature term --
- The basic data structure of Noos. They can be seen as a
generalization of first order terms and lambda terms. They are extendable
records organized in a subsumption hierarchy. See
- Identifier --
- An identifier is a symbol denoting a term. Terms that
have an identifier are named terms and others are anonymous
- Inheritance --
- Inheritance involve two different aspects that are
distinguished in Noos: subtyping and code reuse. Subtyping is modeled
by subsumption and code reuse is achieved by refinement.
- Matching --
- See subsumption.
- Memorization --
- The property of permanent terms to be stored
in permanent memory and be amenable to retrieval.
- Metalevel --
- A feature term in a metalevel relationship with a
referent term. See §2.4.
- Method --
- An evaluable feature term. Formally, a function that
receives parameters by feature names. A method term is closed
when it possess all required parameters. A non-closed method can be
defined by refinement--this is equivalent to partial evaluation or
currying. Application of a non-closed method yields an error.
- Named Term --
- A term with an identifier. A named term can be
referenced by its identifier using (>> of NamedTerm) although syntactic
sugar allows in some places to only write NamedTerm.
- Path reference --
- The mechanism by which equality constrains are
established. A path reference is a way to refer a term by the position it
has as a subterm of another term. An absolute path reference has a form
like (>> father mother of jack) while a relative path
reference has a form like (>> father mother) and refers to the
root of the description it occurs in.
- Permanent terms --
- Feature terms that are memorized (see
memorization) and thus amenable to retrieval.
- Root --
- The root node of a feature term is the outmost in a
description. For instance, the root in
(define (person Jack) (girlfriend (define (girl))))
is the node with identifier Jack and constituent person.
- Query --
- A question that is asked by the system. Usually, a query is
asking for a feature value, as in (>> diganosis of patient-33).
Since evaluation is lazy, no feature values inferred until a query is
performed--and only those feature values needed will be computed.
- Reference --
- See identifier and path reference.
- Referent --
- The referent of a metalevel is that term it
is metalevel of. The referent of a task is the result value of that
- Refinement --
- An constructor operation that builds a term from
another (already defined) term. The constructed term has a root with
constituent the identifier of the root of the original term.
For instance an alien person from Mars (the PC way to say Martian)
can be refined from person as follows: (define (person
Martian) (planet Mars)). The root is Martian and has
person as constituent. Refinement permits overriding, and in the
example Martian overrides planet to be Mars--when formerly had
been Earth. Thus, refinement does not imply subsumption. See
- Retrieval --
- The capability of referring to permanent terms other
than by identifiers or path references.
- Slot --
- A slot is a pair consisting of a label (or feature name or
field name) and a feature value (that can be a feature term, a string, a
number or an identifier).
- Subsumption --
- Checking whether one description implies another. For
instance person subsumes (define (person) (age 23)).
Subsumption corresponds to logical implication.
- Symbol --
- See identifier.
- Task --
- The process of establishing the value of a feature.
Noos reifies a task object that maintain some information of the
status of a task.
Next: Feature Terms
Previous: Basic Syntax
Thu Jan 23 11:36:28 MET 1997