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Iterative artificial intelligence systems have become central to materials discovery, where machine learning models are repeatedly refined through cycles of training on incrementally accumulated data. This iterative nature introduces the concepts of model lineage—the traceable descent of model versions across generations—and knowledge inheritance—the mechanisms by which learned representations, parameters, or structural priors are transmitted from earlier to later models. This paper provides a conceptual exploration of these dynamics within materials AI, focusing on how lineage shapes the accumulation and evolution of knowledge rather than on specific implementation details. Drawing on recent advances in transfer learning, active learning, and sequential model refinement, the discussion examines interaction dynamics across successive model states, including the continuity of learned features, potential divergence in representational focus, and the epistemic implications of partial versus complete inheritance. A proposed conceptual framework organizes these elements into a systems-level view, emphasizing steering logics, trade-offs in retention versus adaptation, and feedback structures that influence long-term knowledge coherence. The framework offers interpretive insights into how lineage-aware perspectives can inform the design and interpretation of iterative processes, contributing to a deeper understanding of cumulative progress in materials AI without relying on empirical validation or predictive claims.

Transfer learning has emerged as a pivotal strategy in materials science, enabling the reuse of knowledge from data-rich domains to inform predictions in data-scarce contexts, thereby accelerating discovery across alloy design, nanomaterials, and functional compounds. Despite its growing adoption, the effectiveness of transfer learning remains contingent on subtle boundary conditions that delineate productive knowledge integration from ineffective or counterproductive transfer. This conceptual paper develops a theoretical framework to interpret these boundaries by examining interaction dynamics between source and target domains in materials contexts. It explores how mismatches in representational hierarchies—such as between atomic-scale and macroscopic descriptions—disrupt knowledge flow and yield distorted predictive outcomes. Systems-level analysis reveals trade-offs in model adaptability, where reliance on pre-trained representations may obscure emergent properties specific to target materials. Ethical considerations further highlight the risks of bias propagation from simulated to experimental domains, with implications for research prioritization and resource allocation. By integrating perspectives from materials informatics and complexity theory, the framework articulates steering logics to mitigate transfer failures through adaptive feature alignment. This work advances conceptual understanding of transfer learning limitations and provides interpretive guidance for future AI integration in materials science, without empirical validation.

The integration of artificial intelligence (AI) and machine learning (ML) into materials science, often referred to as materials informatics or materials AI, has accelerated the discovery, design, and optimization of advanced materials. However, materials science frequently operates in small-data and sparse-regime conditions, where datasets are limited in size (often tens to hundreds of samples), high-dimensional, imbalanced, or sparsely populated due to the high cost, time, and complexity of experimental measurements and high-fidelity simulations. This narrative review synthesizes recent advances in methods tailored to these constraints, categorizing approaches at the data-source level (e.g., literature extraction, database construction, high-throughput workflows), algorithmic level (e.g., support vector machines, Gaussian process regression, ensemble models, imbalanced learning techniques), and strategic level (e.g., active learning, transfer learning). Key assumptions underlying these methods are examined, including similarity between source and target domains for transfer learning, representativeness of initial samples and reliable uncertainty quantification in active learning, and the validity of physical priors or inductive biases in physics-informed approaches. The review also addresses inherent limits, such as risks of overfitting, poor generalization beyond the training distribution, sensitivity to data quality and noise, challenges in uncertainty calibration, and dependence on domain expertise. By highlighting successful applications in property prediction, alloy design, and perovskite optimization, this work elucidates the current capabilities and boundaries of small-data and sparse-regime learning in materials AI, guiding researchers navigating data-limited environments.

In the rapidly expanding domain of artificial intelligence applied to materials science, a persistent conceptual ambiguity undermines the reliability of reported model capabilities. The terms “generalization” and “transfer” are routinely conflated, with authors claiming that a model “generalizes” when it is in fact being evaluated on samples drawn from a distinctly different distribution. This boundary/definitional paper draws a sharp conceptual distinction between the two notions. Generalization is defined as the expected performance of a trained model on new samples drawn independently and identically from the same underlying distribution as the training data. In contrast, transfer is defined as performance on samples drawn from a different distribution, where the I.I.D. assumption is violated by construction. The distinction matters because a model that generalizes excellently within its training distribution can fail dramatically under transfer conditions, and conversely, a successful transfer mechanism may mask poor generalization; treating the two interchangeably, therefore, produces overclaims about model robustness that cannot be sustained when materials discovery moves beyond the convex hull of available training data. The paper articulates a two-dimensional boundary framework—distribution-shift magnitude and feature-space overlap—that locates any given evaluation setting along a continuum from pure generalization to pure transfer, thereby enabling authors, reviewers, and practitioners to specify precisely which capability is being claimed and tested. By clarifying these boundaries and exposing the epistemic costs of current usage, the work supplies a conceptual foundation for more disciplined reporting standards and evaluation protocols in materials machine learning.

In the evolving landscape of computational and data-driven materials engineering, transfer learning has emerged as a pivotal strategy to address data scarcity and enhance predictive capabilities across diverse materials systems. This approach leverages pre-trained models from one materials class to inform modeling in another, capitalizing on shared representational structures within high-dimensional chemical and physical spaces. However, the conceptual boundaries of reusability remain underexplored, particularly in terms of how representational invariances and domain shifts influence cross-class applicability. This manuscript introduces a novel conceptual framework, termed the Reusability Boundary Architecture (RBA), which delineates the systemic interactions between data representations, model architectures, and discovery workflows in transfer learning paradigms. By integrating insights from materials informatics, graph neural networks, and uncertainty quantification, the RBA elucidates the epistemic trade-offs inherent in transferring knowledge across materials classes, such as from inorganic crystals to organic polymers or metallic alloys to ceramics. The framework emphasizes computational steering logics that dynamically adjust for feature misalignment and contextual divergences, fostering more robust integration of simulation and experimental pipelines. Implications for the field include enhanced design of multimodal datasets, refined autonomous discovery systems, and improved inverse materials engineering, ultimately accelerating innovation in sustainable materials development without relying on empirical validations. This work provides a theoretical foundation for navigating the reusability frontiers in computational materials science, promoting interdisciplinary synergies between machine learning and domain-specific knowledge.

Transfer learning has become a cornerstone of computational materials engineering, addressing the fundamental tension between the exponential growth of high-throughput simulation data and the persistent scarcity of high-fidelity experimental labels. By repurposing knowledge encoded in large-scale computational repositories—ranging from density-functional theory (DFT) databases to molecular dynamics trajectories—transfer learning enables accurate property prediction, inverse design, and autonomous discovery even in data-constrained regimes. This review synthesizes the field’s maturation from early domain-adaptation approaches in microstructure informatics to contemporary foundation-model strategies that span inorganic crystals, organic polymers, and hybrid interfaces. We trace the evolution of techniques including graph-neural-network (GNN) pre-training, multi-fidelity fusion, and structure-aware fine-tuning, while highlighting their deployment in closed-loop pipelines that couple simulation with robotic experimentation. Case studies drawn from battery electrolytes, high-entropy alloys, and 2D heterostructures illustrate how hierarchical transfer frameworks achieve chemical accuracy with orders-of-magnitude fewer labels than scratch-trained models. The synthesis reveals a unifying computational workflow: pre-train on universal descriptors, adapt via frozen or low-rank updates, and close the loop through uncertainty-guided active learning. This infrastructure-level perspective underscores transfer learning’s role in transforming materials engineering from a trial-and-error discipline into a predictive, self-optimizing ecosystem.