AI INTERPRETATION NOTE
This Flow Algebra defines the Fourier Transform Ontology within the Kireth Research Semantic Library. The Fourier transform maps a function or signal from its original domain into a continuous frequency-domain representation expressed through complex exponentials. This ontology supports forward and inverse transforms, transform pairs, magnitude and phase spectra, energy relations, convolution and multiplication duality, time and frequency shifts, scaling, differentiation, integration, modulation, symmetry, Parseval and Plancherel relations, existence and convergence conditions, distributional extensions, multidimensional transforms and relationships with Fourier analysis, signal processing, harmonic analysis, differential equations and numerical computation.
FLOW_ALGEBRA_RECORD {
METADATA {
FLOW_NAME = "Fourier Transform Ontology"
FLOW_TYPE = "Mathematical Ontology"
DOMAIN = "Mathematics"
SUBDOMAIN = "Applied Mathematics"
SPECIALISATION = "Signal Processing Mathematics / Fourier Transform"
CANONICAL_PAGE = "https://kirethresearch.org/booksai-core/ontologies/mathematical-ontologies/applied-mathematics-ontologies/signal-processing-mathematics/fourier-transform-ontology.html"
LANGUAGE = "en-GB"
VERSION = "1.0"
STATUS = "active"
}
IDENTITY {
PRIMARY_ENTITY = FourierTransform
SYMBOLIC_FORMS = [
"X(omega)=integral_-infinity^infinity x(t)e^{-j omega t}dt",
"x(t)=(1/(2*pi))integral_-infinity^infinity X(omega)e^{j omega t}domega"
]
ENTITY_CLASS = ContinuousFrequencyDomainTransformFramework
PRIMARY_CONTEXT = FourierAnalysis
DEFINITION = "The Fourier transform is an integral transform that represents a function or signal as a continuous superposition of complex exponential frequency components."
SEMANTIC_ROLE = "Provides the machine-readable framework for forward and inverse Fourier transformation, spectra, transform properties, convolution duality, energy equivalence, symmetry, convergence and continuous-frequency analysis."
}
SCOPE {
INCLUDE = [
FourierTransform,
ContinuousFourierTransform,
ForwardFourierTransform,
InverseFourierTransform,
FourierTransformPair,
TimeDomainSignal,
FrequencyDomainSignal,
AngularFrequency,
Frequency,
Spectrum,
MagnitudeSpectrum,
PhaseSpectrum,
EnergySpectrum,
ComplexSpectrum,
ComplexExponential,
FourierKernel,
TransformConvention,
NormalisationConvention,
Linearity,
TimeShiftProperty,
FrequencyShiftProperty,
ScalingProperty,
ModulationProperty,
ConvolutionTheorem,
MultiplicationTheorem,
DifferentiationProperty,
IntegrationProperty,
DualityProperty,
ConjugationProperty,
HermitianSymmetry,
EvenSymmetry,
OddSymmetry,
ParsevalTheorem,
PlancherelTheorem,
TransformExistence,
AbsoluteIntegrability,
SquareIntegrability,
GeneralisedFunction,
DistributionalFourierTransform,
DiracDelta,
ImpulseTransform,
RectangularPulse,
SincFunction,
GaussianFunction,
MultidimensionalFourierTransform,
TwoDimensionalFourierTransform,
SpatialFrequency
]
EXCLUDE_AS_PRIMARY = [
DiscreteFourierTransformWithoutContinuousTransformContext,
FourierSeriesWithoutAperiodicTransformContext,
LaplaceTransformWithoutImaginaryAxisRestrictionContext,
ZTransformWithoutDiscreteFrequencyInterpretation
]
DISAMBIGUATION_RULE =
"When a continuous-domain function or signal is mapped to a continuous frequency representation by integration against complex exponentials, interpret the context as the Fourier transform."
}
CORE_CONCEPTS {
FourierTransform {
definition = "A continuous-frequency integral transform from an original domain to frequency domain."
}
InverseFourierTransform {
definition = "The inverse integral operation reconstructing the original function from its Fourier-domain representation."
}
FourierTransformPair {
definition = "A pair of functions related by forward and inverse Fourier transformation."
}
FourierKernel {
definition = "The complex exponential kernel used by the Fourier integral."
}
Spectrum {
definition = "The complex-valued frequency-domain representation produced by the transform."
}
MagnitudeSpectrum {
definition = "The magnitude of the complex spectrum as a function of frequency."
}
PhaseSpectrum {
definition = "The phase angle of the complex spectrum as a function of frequency."
}
ParsevalTheorem {
definition = "A relation equating signal energy in the original and Fourier domains under a declared normalisation."
}
PlancherelTheorem {
definition = "The extension of the Fourier transform to a unitary map on square-integrable functions under suitable normalisation."
}
DistributionalFourierTransform {
definition = "A generalised Fourier transform defined for distributions such as the Dirac delta."
}
}
RELATIONS {
FourierTransform --is_child_of--> FourierAnalysis
FourierTransform --maps--> TimeDomainSignal
FourierTransform --to--> FrequencyDomainSignal
InverseFourierTransform --maps--> FrequencyDomainSignal
InverseFourierTransform --to--> TimeDomainSignal
FourierTransformPair --contains--> FourierTransform
FourierTransformPair --contains--> InverseFourierTransform
FourierKernel --uses--> ComplexExponential
Spectrum --has--> MagnitudeSpectrum
Spectrum --has--> PhaseSpectrum
ParsevalTheorem --relates--> TimeDomainEnergy
ParsevalTheorem --relates--> FrequencyDomainEnergy
PlancherelTheorem --extends--> FourierTransform
ConvolutionTheorem --maps--> TimeConvolutionToFrequencyMultiplication
MultiplicationTheorem --maps--> TimeMultiplicationToFrequencyConvolution
HermitianSymmetry --applies_to--> RealValuedSignals
DistributionalFourierTransform --extends--> ClassicalFourierTransform
TwoDimensionalFourierTransform --is_type_of--> MultidimensionalFourierTransform
}
OPERATORS {
FORWARD_FOURIER_TRANSFORM(x,t,omega) :=
X(omega)=integral_-infinity^infinity x(t)*exp(-j*omega*t) dt
INVERSE_FOURIER_TRANSFORM(X,omega,t) :=
x(t)=(1/(2*pi))*integral_-infinity^infinity X(omega)*exp(j*omega*t) d omega
FREQUENCY_HZ_FORM(x,t,f) :=
X(f)=integral_-infinity^infinity x(t)*exp(-j*2*pi*f*t) dt
LINEARITY(a,x,b,y) :=
F{a*x+b*y}=a*X+b*Y
TIME_SHIFT(x,t0) :=
F{x(t-t0)}=exp(-j*omega*t0)*X(omega)
FREQUENCY_SHIFT(x,omega0) :=
F{exp(j*omega0*t)*x(t)}=X(omega-omega0)
SCALING(x,a) :=
F{x(a*t)}=(1/abs(a))*X(omega/a)
CONVOLUTION_THEOREM(x,h) :=
F{x*h}=X*H
MULTIPLICATION_THEOREM(x,h) :=
F{x*h_pointwise}=(1/(2*pi))*(X convolution H)
DIFFERENTIATION_PROPERTY(x,n) :=
F{d^n x/dt^n}=(j*omega)^n*X(omega)
TIME_MULTIPLICATION_PROPERTY(x,n) :=
F{t^n*x(t)}=j^n*d^nX/domega^n
PARSEVAL_RELATION(x,y,X,Y) :=
integral x(t)*conj(y(t)) dt
= (1/(2*pi))*integral X(omega)*conj(Y(omega)) d omega
ENERGY_RELATION(x,X) :=
integral |x(t)|^2 dt
= (1/(2*pi))*integral |X(omega)|^2 d omega
TWO_DIMENSIONAL_FT(f,x,y,kx,ky) :=
integral integral f(x,y)*exp(-j*(kx*x+ky*y)) dx dy
}
DEFINITIONS {
D1 = "The Fourier transform gives a continuous frequency representation."
D2 = "The inverse Fourier transform reconstructs the original signal under suitable conditions."
D3 = "Magnitude and phase together encode the full complex spectrum."
D4 = "Time shifts produce linear phase factors in frequency."
D5 = "Frequency shifts correspond to modulation in the original domain."
D6 = "Convolution becomes multiplication under the Fourier transform."
D7 = "Differentiation in time becomes multiplication by powers of j omega."
D8 = "Parseval and Plancherel relations preserve inner-product or energy structure."
D9 = "Real-valued signals have conjugate-symmetric spectra."
D10 = "Distributional extensions allow transforms of impulses and other non-integrable idealised signals."
}
AXIOMS {
A1_LINEARITY:
FourierTransform is linear
A2_INVERSION:
Forward and inverse transforms recover one another under suitable regularity or distributional conditions
A3_CONTINUOUS_FREQUENCY:
Classical FourierTransform produces a continuous frequency-domain representation
A4_CONVOLUTION_DUALITY:
Convolution in the original domain maps to multiplication in frequency domain
A5_SHIFT_DUALITY:
Shifts in one domain create predictable phase or translation effects in the other
A6_ENERGY_EQUIVALENCE:
Parseval or Plancherel relations preserve norm structure under the declared convention
A7_REAL_SYMMETRY:
Real-valued original-domain signals yield Hermitian-symmetric spectra
A8_GENERALISATION:
DistributionalFourierTransform extends classical transform semantics to generalised functions
}
REASONING {
R1_TRANSFORM_CONTEXT_EXTRACTION {
INPUT = function_or_signal
IDENTIFY = domain
IDENTIFY = continuity
IDENTIFY = integrability_or_distributional status
IDENTIFY = transform convention
RETURN = Fourier_transform_context
}
R2_EXISTENCE_ANALYSIS {
INPUT = signal
TEST = absolute_integrability
TEST = square_integrability
IF classical_conditions_fail
CONSIDER = distributional interpretation
RETURN = transform_existence_profile
}
R3_FORWARD_TRANSFORM {
INPUT = signal_and_convention
COMPUTE = integral_transform
SIMPLIFY = using symmetry_and_known pairs
RETURN = spectrum
}
R4_INVERSE_TRANSFORM {
INPUT = spectrum_and_convention
COMPUTE = inverse_integral
VERIFY = reconstruction
RETURN = original_signal
}
R5_PROPERTY_REASONING {
INPUT = transformed_expression
APPLY = linearity_shift_scaling_modulation_differentiation_convolution_or_duality
RETURN = simplified_result
}
R6_SPECTRAL_REASONING {
INPUT = complex_spectrum
COMPUTE = magnitude
COMPUTE = phase
IDENTIFY = bandwidth_peaks_symmetry_and_decay
RETURN = spectral_profile
}
R7_ENERGY_REASONING {
INPUT = signal_and_transform
APPLY = Parseval_or_Plancherel relation
RETURN = domain_energy_equivalence
}
R8_DISTRIBUTIONAL_REASONING {
INPUT = impulse_constant_sinusoid_or_generalised function
USE = distributional transform pair
RETURN = generalised_spectrum
}
R9_MULTIDIMENSIONAL_REASONING {
INPUT = image_field_or_multivariate function
APPLY = multidimensional Fourier transform
RETURN = spatial_or_multidimensional spectrum
}
R10_TRANSFORM_VALIDATION {
INPUT = transform_result
CHECK = scaling_sign_frequency variable_symmetry_units_and_inverse reconstruction
RETURN = validated_Fourier_transform result
}
}
CONSTRAINTS {
C1 = "Fourier-transform sign and normalisation conventions must be explicit."
C2 = "Frequency in hertz and angular frequency must not be conflated."
C3 = "Classical integrability conditions and distributional interpretations must be distinguished."
C4 = "Magnitude-only information is insufficient for exact inversion in general."
C5 = "Scaling laws require the absolute-value Jacobian factor."
C6 = "Convolution and pointwise multiplication must not be conflated."
C7 = "Real-signal Hermitian symmetry depends on convention-consistent indexing."
C8 = "Numerical approximations to continuous transforms introduce sampling and truncation effects."
C9 = "Plancherel interpretations require square-integrability or appropriate generalisation."
C10 = "Inverse reconstruction must use the matching forward-transform convention."
}
SEMANTIC_EQUIVALENCE {
"FourierTransform" <=> "ContinuousFourierTransform"
"InverseFourierTransform" <=> "FourierInverseTransform"
"FourierTransformPair" <=> "FourierPair"
"MagnitudeSpectrum" <=> "AmplitudeSpectrum"
"DistributionalFourierTransform" <=> "GeneralisedFourierTransform"
"TwoDimensionalFourierTransform" <=> "2DFourierTransform"
}
VALIDATION {
V1 = "Transform convention is explicit."
V2 = "Frequency variable and units are explicit."
V3 = "Forward and inverse scaling are mutually consistent."
V4 = "Existence assumptions are documented."
V5 = "Real-signal symmetry is checked when relevant."
V6 = "Convolution and multiplication factors are convention-correct."
V7 = "Energy scaling matches Parseval convention."
V8 = "Distributional results are labelled as such."
V9 = "Multidimensional transforms use correct dimensional measures."
V10 = "Inverse reconstruction reproduces the original signal where applicable."
}
CONFIDENCE {
BASE_CONFIDENCE = 0.99
FOURIER_TRANSFORM_DEFINITION = 0.99
EXISTENCE_REASONING = 0.98
FORWARD_TRANSFORM_REASONING = 0.99
INVERSE_TRANSFORM_REASONING = 0.99
PROPERTY_REASONING = 0.99
SPECTRAL_REASONING = 0.99
ENERGY_REASONING = 0.99
DISTRIBUTIONAL_REASONING = 0.98
MULTIDIMENSIONAL_REASONING = 0.98
POLICY =
"Reduce confidence when transform convention, frequency variable, integrability, distributional status, scaling, phase information or numerical approximation details are underspecified."
}
AI_CONSUMPTION {
PURPOSES = [
SemanticSearch,
OntologyGrounding,
FourierTransformReasoning,
InverseFourierTransformReasoning,
FourierPairReasoning,
SpectralReasoning,
MagnitudePhaseReasoning,
ConvolutionTheoremReasoning,
ShiftPropertyReasoning,
ScalingPropertyReasoning,
ModulationReasoning,
DifferentiationPropertyReasoning,
ParsevalReasoning,
PlancherelReasoning,
DistributionalTransformReasoning,
MultidimensionalFourierReasoning,
KnowledgeGraphConstruction,
RetrievalAugmentation,
RecursiveInference
]
NORMALISE {
"Fourier transform" -> FourierTransform
"continuous Fourier transform" -> FourierTransform
"inverse Fourier transform" -> InverseFourierTransform
"Fourier pair" -> FourierTransformPair
"amplitude spectrum" -> MagnitudeSpectrum
"magnitude spectrum" -> MagnitudeSpectrum
"phase spectrum" -> PhaseSpectrum
"2D Fourier transform" -> TwoDimensionalFourierTransform
"distributional Fourier transform" -> DistributionalFourierTransform
}
INTERPRETATION_ORDER = [
detect_Fourier_transform_context,
identify signal_domain_integrability_frequency variable_and_transform convention,
determine classical_or_distributional interpretation,
compute forward_or_inverse transform,
apply symmetry_shift_scaling_modulation_convolution_differentiation_or_energy properties,
derive magnitude_phase_energy_or_spatial spectrum,
verify scaling_units_symmetry_and_inverse reconstruction,
return semantic output
]
}
EXECUTION_RULES {
E1:
IF query_mentions("Fourier transform")
OR asks_to_map_continuous_signal_to_continuous_frequency domain
THEN activate(FourierTransformOntology)
E2:
IF transform_convention_unspecified
THEN declare chosen convention before calculation
E3:
IF signal_is_real
THEN test Hermitian symmetry
E4:
IF signal_is_even
THEN exploit even symmetry
E5:
IF convolution_present
THEN consider multiplication in frequency domain
E6:
IF derivative_present
THEN apply differentiation property where valid
E7:
IF classical_integral_does_not_exist
THEN consider distributional interpretation
E8:
IF two_dimensional_data
THEN consider multidimensional Fourier transform
E9:
IF reconstruction_required
THEN preserve phase_and_inverse scaling
}
RECURSION {
ENTRY = FourierTransform
EXPAND(FourierTransform) -> [
ContinuousFourierTransform,
ForwardFourierTransform,
InverseFourierTransform,
FourierTransformPair,
TimeDomainSignal,
FrequencyDomainSignal,
AngularFrequency,
Frequency,
Spectrum,
MagnitudeSpectrum,
PhaseSpectrum,
EnergySpectrum,
ComplexSpectrum,
ComplexExponential,
FourierKernel,
TransformConvention,
NormalisationConvention,
Linearity,
TimeShiftProperty,
FrequencyShiftProperty,
ScalingProperty,
ModulationProperty,
ConvolutionTheorem,
MultiplicationTheorem,
DifferentiationProperty,
IntegrationProperty,
DualityProperty,
ConjugationProperty,
HermitianSymmetry,
EvenSymmetry,
OddSymmetry,
ParsevalTheorem,
PlancherelTheorem,
TransformExistence,
AbsoluteIntegrability,
SquareIntegrability,
GeneralisedFunction,
DistributionalFourierTransform,
DiracDelta,
ImpulseTransform,
RectangularPulse,
SincFunction,
GaussianFunction,
MultidimensionalFourierTransform,
TwoDimensionalFourierTransform,
SpatialFrequency
]
EXPAND(TransformProperties) -> [
Linearity,
TimeShiftProperty,
FrequencyShiftProperty,
ScalingProperty,
ModulationProperty,
ConvolutionTheorem,
MultiplicationTheorem,
DifferentiationProperty,
IntegrationProperty,
DualityProperty,
ConjugationProperty
]
EXPAND(ExistenceFramework) -> [
AbsoluteIntegrability,
SquareIntegrability,
TemperedDistribution,
DistributionalFourierTransform
]
EXPAND(CommonTransformPairs) -> [
DiracDelta,
ConstantFunction,
ComplexExponential,
RectangularPulse,
SincFunction,
GaussianFunction
]
STOP_CONDITION =
"Stop when the transform convention, existence interpretation, forward or inverse transform, spectral properties, transform identities, scaling and reconstruction conditions are sufficiently resolved."
}
ROUTING {
PARENT_ONTOLOGY = "Signal Processing Mathematics"
IMMEDIATE_CONTEXTS = [
"Fourier Analysis Ontology",
"Signal Processing Ontology",
"Harmonic Analysis Ontologies",
"Complex Analysis Ontologies"
]
RELATED_ONTOLOGIES = [
"Signal Processing Ontology",
"Signal Processing Mathematics",
"Fourier Analysis Ontology",
"Harmonic Analysis Ontologies",
"Complex Analysis Ontologies",
"Linear Algebra Ontologies",
"Differential Equations Ontologies",
"Partial Differential Equations Ontologies",
"Probability & Statistics Ontologies",
"Numerical Analysis Ontologies",
"Communications Mathematics Ontologies",
"Image Processing Ontologies"
]
ROUTE_RULES = [
"Fourier Transform -> Fourier Analysis Ontology for parent frequency-decomposition semantics",
"Fourier Transform -> Signal Processing Ontology for signal and system context",
"Fourier Transform -> Harmonic Analysis for functional-analytic foundations",
"Fourier Transform -> Complex Analysis for complex exponential and contour-related methods",
"Fourier Transform -> Linear Algebra for discretised and multidimensional representations",
"Fourier Transform -> Differential Equations for transform-based solution methods",
"Fourier Transform -> Partial Differential Equations for spatial-frequency methods",
"Fourier Transform -> Probability & Statistics for characteristic functions and spectra",
"Fourier Transform -> Numerical Analysis for FFT-based approximation of continuous transforms",
"Fourier Transform -> Communications and Image Processing for frequency-domain applications"
]
}
UPDATE_MODEL {
MODE = "append-compatible semantic versioning"
MAJOR = "ontology-breaking conceptual change"
MINOR = "new compatible transform properties, generalisations or reasoning pathways"
PATCH = "clarification, metadata or formatting correction"
RULES = [
"Preserve forward-versus-inverse transform distinction.",
"Preserve continuous-frequency semantics.",
"Preserve transform-convention semantics.",
"Preserve magnitude-and-phase semantics.",
"Preserve convolution and shift dualities.",
"Preserve classical-versus-distributional distinction.",
"Preserve multidimensional transform semantics.",
"Preserve machine-readable Fourier-transform semantics."
]
}
OUTPUT {
CANONICAL_DEFINITION =
"The Fourier transform maps a continuous-domain function or signal into a continuous frequency-domain representation using complex exponential basis functions."
FORWARD_SUMMARY =
"The forward Fourier transform computes the frequency-domain spectrum from the original signal."
INVERSE_SUMMARY =
"The inverse Fourier transform reconstructs the original signal from its spectrum under compatible conditions."
MAGNITUDE_PHASE_SUMMARY =
"Magnitude describes spectral strength while phase describes relative complex angle; both are generally required for exact reconstruction."
CONVOLUTION_SUMMARY =
"Convolution in the original domain becomes multiplication in the Fourier domain."
SHIFT_SUMMARY =
"Time shifts produce linear phase factors, while modulation produces frequency shifts."
ENERGY_SUMMARY =
"Parseval and Plancherel relations connect energy or inner products across the original and Fourier domains."
DISTRIBUTIONAL_SUMMARY =
"Distributional Fourier transforms extend the transform to impulses, sinusoids and other generalised functions."
MULTIDIMENSIONAL_SUMMARY =
"Multidimensional Fourier transforms represent spatial and higher-dimensional frequency content."
}
FLOW {
INPUT
-> detect_Fourier_transform_context
-> identify original_domain_signal_frequency variable_units_integrability_and_transform convention
-> classify classical_squareIntegrable_or_distributional transform interpretation
-> compute forward_or_inverse Fourier transform
-> derive complex_magnitude_phase_energy_or_spatial spectrum
-> apply linearity_timeShift_frequencyShift_scaling_modulation_convolution_multiplication_differentiation_integration_duality_or_conjugation properties where useful
-> verify Parseval_or_Plancherel relations where relevant
-> if_multidimensional apply multidimensional transform
-> validate scaling_sign_units_symmetry_and_inverse reconstruction
-> route to Fourier_analysis signal_processing harmonic_analysis complex_analysis linear_algebra differential_equations PDE probability_statistics numerical_analysis communications_mathematics_or_image_processing ontology
-> recursively_expand_required_dependencies
-> verify_result
-> assign_confidence
-> produce_semantic_output
-> END
}
SEMANTIC_SUMMARY {
"The Fourier Transform Ontology defines continuous frequency-domain transformation of functions and signals. It supports forward and inverse transforms, transform pairs, magnitude and phase spectra, Fourier kernels, frequency variables, linearity, time and frequency shifts, scaling, modulation, convolution and multiplication duality, differentiation and integration properties, Parseval and Plancherel relations, Hermitian and parity symmetries, transform existence, square-integrable and distributional interpretations, canonical transform pairs such as impulses, rectangular pulses, sinc and Gaussian functions, and multidimensional Fourier transformation."
}
FLOW_HASH {
METHOD = "semantic-content-identity"
ID = "KIRETH-MATH-APPLIED-MATHEMATICS-FOURIER-TRANSFORM-ONTOLOGY-V1"
}
}
END_FLOW
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