Bridging Structured Knowledge and Data: A Unified Framework with Finance Applications
Organizations: Department of Financial and Actuarial Mathematics, Xi’an Jiaotong-Liverpool University, Suzhou, Jiangsu 215123, PR China. · Management Science and Business Economics Group, Business School, University of Edinburgh, 29 Buccleuch Place, Edinburgh EH8 9JS, UK. · Nanyang Technological University, ABFER, CEPR, & NBER, 91 Nanyang Avenue, Wee Cho Yaw Plaza, Singapore 639956.
Abstract
We develop Structured-Knowledge-Informed Neural Networks (SKINNs), a unified estimation framework that embeds theoretical, simulated, previously learned, or cross-domain insights as differentiable constraints within flexible neural function approximation. SKINNs jointly estimate neural network parameters and economically meaningful structural parameters in a single optimization problem, enforcing theoretical consistency not only on observed data but over a broader input domain through collocation, and therefore nesting approaches such as functional GMM, Bayesian updating, transfer learning, PINNs, and surrogate modeling. SKINNs define a class of M-estimators that are consistent and asymptotically normal with root-N convergence, sandwich covariance, and recovery of pseudo-true parameters under misspecification. We establish identification of structural parameters under joint flexibility, derive generalization and target-risk bounds under distributional shift in a convex proxy, and provide a restricted-optimal characterization of the weighting parameter that governs the bias-variance tradeoff. In an illustrative financial application to option pricing, SKINNs improve out-of-sample valuation and hedging performance, particularly at longer horizons and during high-volatility regimes, while recovering economically interpretable structural parameters with improved stability relative to conventional calibration. More broadly, SKINNs provide a general econometric framework for combining model-based reasoning with high-dimensional, data-driven estimation.
Figures & tables
| Model | Structured Knowledge 9 9 9 “No” in the column structured knowledge means that there is no prior knowledge; “Bnd” means that the boundary conditions are incorporated; “Shape” means that the model-free shape constraints are incorporated; and “AE-BSM” means the machine-learned AE-based NPSKR structured-knowledge function from the BSM model with noise; “AE-MIX” means such a structured-knowledge function from the mixture of models with noise. | (learnable/total) | Activation function |
| Benchmark NNs | |||
| NN | No | 0/0 | ReLU |
| NN+Bnd | Bnd | 0/0 | ReLU |
| NN+Shape | Shape | 0/0 | SiLU |
| PINN+BSM | BSM | 1/1 | SiLU |
| TLNN+HSV | HSV | 0/5 | ReLU |
| Model | Structural models | Benchmark NNs | ||||||
| Panel (A) | BSM | ABSM | HSV | HSVJ | NN | NN | NN | PINN |
| +Bnd | +Shape | +BSM | ||||||
| BSM | – | 1.99** | -2.16** | -9.24*** | -1.72** | -2.42*** | 0.16 | 0.21 |
| ABSM | – | – | -2.89*** | -8.91*** | -1.88** | -2.58*** | -0.07 | -0.02 |
| HSV | – | – | – | -12.95*** | -1.49* | -2.22** | 0.59 | 0.64 |
| HSVJ | – | – | – | – | -0.61 | -1.35* | 1.81** | 1.85** |
| Model | Structural models | Benchmark NNs | ||||||
| Panel (A) | BSM | ABSM | HSV | HSVJ | NN | NN | NN | PINN |
| +Bnd | +Shape | +BSM | ||||||
| BSM | – | 2.49*** | 0.62 | -5.23*** | 2.67*** | 1.36* | 2.51*** | 2.54*** |
| ABSM | – | – | -0.57 | -5.83*** | 2.56*** | 1.26 | 2.40*** | 2.42*** |
| HSV | – | – | – | -12.95*** | 2.63*** | 1.33* | 2.45*** | 2.47*** |
| HSVJ | – | – | – | – | 3.09*** | 1.74** | 2.94*** | 2.97*** |
| Model | Structural models | Benchmark NNs | ||||||
| Panel (A) | BSM | ABSM | HSV | HSVJ | NN | NN | NN | PINN |
| +Bnd | +Shape | +BSM | ||||||
| BSM | – | -3.62*** | 6.63*** | 6.56*** | 2.64*** | 2.82*** | 2.99*** | 2.48*** |
| ABSM | – | – | 6.92*** | 6.83*** | 2.90*** | 3.19*** | 3.17*** | 2.66*** |
| HSV | – | – | – | -1.31* | -1.65** | -2.59*** | -0.12 | -0.31 |
| HSVJ | – | – | – | – | -1.55* | -2.49*** | 0.01 | -0.21 |
| Model | Structural models | Benchmark NNs | ||||||
| Panel (A) | BSM | ABSM | HSV | HSVJ | NN | NN | NN | PINN |
| +Bnd | +Shape | +BSM | ||||||
| BSM | – | -4.30*** | 7.69*** | 7.67*** | 3.44*** | 3.48*** | 3.52*** | 3.20*** |
| ABSM | – | – | 7.83*** | 7.81*** | 3.68*** | 3.83*** | 3.72*** | 3.43*** |
| HSV | – | – | – | -1.42* | 0.25 | -1.15 | 1.11 | 0.20 |
| HSVJ | – | – | – | – | 0.39 | -0.99 | 1.21 | 0.32 |
| Model | Frozen/Trainable layers | Learning rate | Epochs | Inputs | |
| DSNN+HSV | 6/0 | 2E-4 | 500 | Simulated | |
| TLNN+HSV1 | 0/6 | 6E-6 | 6 | SKINN-learned | |
| TLNN+HSV2 | 4/2 | 6E-6 | 6 | SKINN-learned | |
| TLNN+HSV3 | 4/2 | 6E-6 | 100 | SKINN-learned | |
| TLNN+HSV4 | 4/2 | 6E-6 | 500 | SKINN-learned | |
| SKINN+HSV | 0/3 | 1E-3 | 500 | – |
| Model | DSNN | TLNN | TLNN | TLNN | TLNN | SKINN |
| +HSV | +HSV1 | +HSV2 | +HSV3 | +HSV4 | +HSV | |
| DSNN+HSV | – | -10.48*** | -10.88*** | -10.48*** | -11.39*** | -13.87**** |
| TLNN+HSV1 | – | – | 9.12*** | -10.37*** | -13.71*** | -11.30*** |
| TLNN+HSV2 | – | – | – | -10.59*** | -13.70*** | -11.60*** |
| TLNN+HSV3 | – | – | – | – | -22.46*** | -6.63*** |
| TLNN+HSV4 | – | – | – | – | – | -2.80*** |
| Model | BSM | ABSM | HSV | HSVJ | NN | – | – | – |
| Panel (A) | +Bnd | |||||||
| 0.0843 ∗∗∗ | 0.0891 ∗∗∗ | 0.0563 ∗∗∗ | 0.0720 ∗∗∗ | -0.0116 ∗ | – | – | – | |
| (0.0141) | (0.0140) | (0.0146) | (0.0143) | (0.0069) | – | – | – | |
| -0.0134 ∗∗∗ | -0.0141 ∗∗∗ | -0.0082 ∗∗ | -0.0151 ∗∗∗ | 0.0005 | – | – | – | |
| (0.0031) | (0.0031) | (0.0032) | (0.0032) | (0.0015) | – | – | – | |
| Obs | 317 | 317 | 317 | 317 | 317 | – | – | – |
| Model | BSM | ABSM | HSV | HSVJ | NN | – | – | – |
| Panel (A) | +Bnd | |||||||
| -0.0317 | -0.0274 | -0.0483 ∗∗ | -0.0340 | -0.0303 ∗∗∗ | – | – | – | |
| (0.0214) | (0.0214) | (0.0215) | (0.0216) | (0.0096) | – | – | – | |
| 0.0019 | 0.0013 | 0.0053 | -0.0008 | 0.0027 | – | – | – | |
| (0.0047) | (0.0047) | (0.0047) | (0.0048) | (0.0021) | – | – | – | |
| Obs | 317 | 317 | 317 | 317 | 317 | – | – | – |
| Model | BSM | ABSM | HSV | HSVJ | NN | – | – | – |
| Panel (A) | +Bnd | |||||||
| -0.1979 | -0.1172 | -0.1354 | -0.1288 | -0.0346 | – | – | – | |
| (0.1657) | (0.1644) | (0.1646) | (0.1671) | (0.1192) | – | – | – | |
| 0.0230 | 0.0125 | 0.0167 | 0.0119 | 0.0024 | – | – | – | |
| (0.0205) | (0.0204) | (0.0204) | (0.0207) | (0.0148) | – | – | – | |
| Obs | 64 | 64 | 64 | 64 | 64 | – | – | – |
| Model | BSM | ABSM | HSV | HSVJ | NN | – | – | – |
| Panel (A) | +Bnd | |||||||
| -0.0708 | -0.0630 | -0.1299 ∗∗ | -0.0974 ∗ | -0.0686 ∗∗ | – | – | – | |
| (0.0525) | (0.0525) | (0.0524) | (0.0532) | (0.0275) | – | – | – | |
| 0.0086 | 0.0075 | 0.0202 ∗∗ | 0.0104 | 0.0098 ∗ | – | – | – | |
| (0.0102) | (0.0103) | (0.0102) | (0.0104) | (0.0054) | – | – | – | |
| Obs | 189 | 189 | 189 | 189 | 189 | – | – | – |
| Model | BSM | ABSM | HSV | HSVJ | NN | – | – | – |
| Panel (A) | +Bnd | |||||||
| -0.0364 | -0.0416 | -0.0345 | -0.0272 | -0.0466 | – | – | – | |
| (0.0783) | (0.0787) | (0.0788) | (0.0791) | (0.0287) | – | – | – | |
| 0.0051 | 0.0077 | 0.0025 | -0.0013 | 0.0094 | – | – | – | |
| (0.0262) | (0.0264) | (0.0264) | (0.0265) | (0.0096) | – | – | – | |
| Obs | 64 | 64 | 64 | 64 | 64 | – | – | – |
| BSM | – | – | – | – | – | |
| 1.1181*** | – | – | – | – | – | |
| (18.781) | – | – | – | – | – | |
| 0.0255** | – | – | – | – | – | |
| (2.543) | – | – | – | – | – | |
| Obs | 317 | – | – | – | – | – |
| Adj. | 52.7% | – | – | – | – | – |
| BSM | – | – | – | – | – | |
| 1.0896*** | – | – | – | – | – | |
| (17.329) | – | – | – | – | – | |
| 0.0323*** | – | – | – | – | – | |
| (3.087) | – | – | – | – | – | |
| Obs | 317 | – | – | – | – | – |
| Adj. | 48.6% | – | – | – | – | – |
| MOPA | |||||
| 26.2949 ∗∗∗ | 16.3890 ∗∗∗ | 10.2331 ∗∗∗ | 6.6412 ∗∗∗ | 5.9800 ∗∗∗ | |
| (1.6483) | (0.9353) | (0.5712) | (0.4056) | (0.3548) | |
| 0.1292 ∗∗∗ | 0.1217 ∗∗∗ | 0.1098 ∗∗∗ | 0.1041 ∗∗∗ | 0.0884 ∗∗∗ | |
| (0.0058) | (0.0057) | (0.0062) | (0.0070) | (0.0076) | |
| Obs | 317 | 317 | 317 | 317 | 317 |
| Adj. R 2 | 44.5% | 49.2% | 50.3% | 45.8% | 47.3% |
| DSNN-HSV | – | |||||
| -7.8261 ∗∗ | 167.5138 ∗∗∗ | -12.7938 ∗∗∗ | 1.9625 ∗ | 6.7324 ∗∗∗ | – | |
| (3.6186) | (10.7461) | (3.1635) | (1.0485) | (2.5814) | ||
| 21.1113 ∗∗∗ | 16.3179 ∗∗∗ | 23.6611 ∗∗∗ | 21.8788 ∗∗∗ | 18.8241 ∗∗∗ | – | |
| (0.5378) | (0.4312) | (0.9039) | (0.8771) | (0.7726) | – | |
| Obs | 317 | 317 | 317 | 317 | 317 | – |
| Adj. R 2 | 1.15% | 43.37% | 4.63% | 0.79% | 1.80% | – |
| Model | NN | SKINN ( ) | SKINN ( ) | |||||||||
| Group | Avg % | SD % | SR | Avg % | SD % | SR | Avg % | SD % | SR | |||
| 1-32 | H | 60.73 | 130.07 | 0.47 | 68.22 | 109.78 | 0.62 | 70.83 | 102.91 | 0.69 | ||
| L | 59.29 | 136.54 | 0.43 | 54.78 | 133.41 | 0.41 | 57.77 | 134.48 | 0.43 | |||
| 2-32 | H | 57.01 | 127.73 | 0.45 | 71.86 | 119.78 | 0.60 | 65.32 | 99.71 | 0.66 | ||
| L | 72.12 | 145.66 | 0.50 | 70.98 | 141.31 | 0.50 | 57.19 | 140.62 | 0.41 | |||
| 3-32 | H | 56.57 | 127.98 | 0.44 | 68.94 | 122.60 | 0.56 | 59.45 | 100.10 | 0.59 | ||
Appendix figures & tables7 assets
Supplementary material from the paper’s appendix.
Appendix
| Model | Structural models | Benchmark NNs | ||||||
| Panel (A) | BSM | ABSM | HSV | HSVJ | NN | NN | NN | PINN |
| +Bnd | +Shape | +BSM | ||||||
| BSM | – | 22.48** | 23.43 | 5.68*** | 17.71*** | 14.13*** | 25.18 | 25.34 |
| ABSM | – | – | 22.58* | 5.20*** | 17.15*** | 13.82*** | 24.53 | 25.12 |
| HSV | – | – | – | 2.94*** | 19.13*** | 16.19*** | 25.89 | 26.53 |
| HSVJ | – | – | – | – | 25.74 | 23.54 | 35.30*** | 35.12*** |
| Model | Structural models | Benchmark NNs | ||||||
| Panel (A) | BSM | ABSM | HSV | HSVJ | NN | NN | NN | PINN |
| +Bnd | +Shape | +BSM | ||||||
| BSM | – | 25.23 | 25.75 | 9.68*** | 27.71* | 22.11** | 27.52* | 28.20** |
| ABSM | – | – | 24.24 | 8.48*** | 27.44* | 21.81** | 27.11 | 27.78* |
| HSV | – | – | – | 3.79*** | 27.75* | 22.40** | 27.20 | 28.15** |
| HSVJ | – | – | – | – | 32.41*** | 27.46* | 33.16*** | 34.08*** |
| Model | Structural models | Benchmark NNs | ||||||
| Panel (A) | BSM | ABSM | HSV | HSVJ | NN | NN | NN | PINN |
| +Bnd | +Shape | +BSM | ||||||
| BSM | – | 5.16*** | 46.50*** | 47.13*** | 22.27** | 21.40*** | 25.08 | 24.21 |
| ABSM | – | – | 46.79*** | 47.31*** | 23.79 | 23.39 | 27.21 | 25.96 |
| HSV | – | – | – | 20.19** | 9.80*** | 7.81*** | 12.32*** | 10.56*** |
| HSVJ | – | – | – | – | 9.59*** | 8.12*** | 12.60*** | 10.81*** |
| Model | Structural models | Benchmark NNs | ||||||
| Panel (A) | BSM | ABSM | HSV | HSVJ | NN | NN | NN | PINN |
| +Bnd | +Shape | +BSM | ||||||
| BSM | – | 6.19*** | 46.34*** | 46.83*** | 22.52* | 21.78** | 24.95 | 24.75 |
| ABSM | – | – | 46.59*** | 47.12*** | 23.76 | 23.64 | 27.32* | 26.56 |
| HSV | – | – | – | 20.55** | 12.36*** | 10.91*** | 14.20*** | 12.84*** |
| HSVJ | – | – | – | – | 12.51*** | 11.17*** | 14.49*** | 13.24*** |
| Shorter Prediction Horizons | Longer Prediction Horizons | |||
| Model | SKINN+SABR | SKINN+AE-MIX | SKINN+SABR | SKINN+AE-MIX |
| BSM | -1.22 | -2.74*** | -1.59* | 0.51 |
| ABSM | -1.36* | -2.93*** | -1.81** | 0.37 |
| HSV | -0.96 | -2.58*** | -1.76* | 0.45 |
| HSVJ | -0.17 | -1.51* | -0.81 | 1.03 |
| NN | 0.30 | -1.65** | -3.68*** | -3.23*** |
| All | Low Volatility | ||||
| Model | SKINN+SABR | SKINN+AE-MIX | SKINN+SABR | SKINN+AE-MIX | |
| AvgVIX | -0.0835*** | -0.0821*** | -0.2368 | -0.0765 | |
| (0.019) | (0.012) | (0.161) | (0.118) | ||
| Constant | 0.0096** | 0.0139*** | 0.0259 | 0.0097 | |
| (0.004) | (0.003) | (0.020) | (0.015) | ||
| Obs | 317 | 317 | 64 | 64 | |
| Paradigm | Configuration | Reference |
| Plain neural network | Gu et al. (2020) | |
| PINNs | , | Raissi et al. (2019) |
| Transfer learning | fixed, two-stage training | Pan and Yang (2010) |
| Bayesian MAP estimation | as neg. log-prior | Neal (1996) |
| Regularized / functional GMM | as moment conditions | Hansen (1982) |
| Sieve GMM / Deep GMM | as neural sieve, optimal | Ai and Chen (2003) |
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