Most existing methods for multimodal knowledge graph completion, or MMKGC, blend three kinds of information. Structural information encodes the topology of the graph itself, visual information draws on images associated with entities, and textual information draws on natural-language descriptions. The trouble, as a team of researchers led by Songjiang Li and Peng Wang at Changchun University of Science and Technology points out, is that nearly all current approaches quietly assume the text is always there. In reality, textual descriptions are frequently missing, particularly for rare, new, or obscure entities. When that happens, entity representations weaken and the carefully tuned machinery of modern completion models can wobble or collapse.

The researchers propose a framework called MMA-HNS, a missing-text-aware robustness extension of an earlier hierarchical negative sampling method known as DHNS. Negative sampling, the technique of generating plausible but false triples to train against, is notoriously sensitive to the quality of entity representations. If the textual modality vanishes for some entities, the multimodal conditions that hierarchical negative sampling depends on become unstable, and the model can waste capacity on poorly chosen negatives. MMA-HNS is designed to keep the whole pipeline steady even when a substantial fraction of entities have no text at all.

The first component is elegantly simple: a learnable missing-text token. Instead of dropping text-missing entities into a special processing branch, the model gives them a continuous proxy representation, a learned placeholder that stands in for the absent description. This preserves a unified multimodal pathway, so the rest of the architecture never has to special-case the missing entities. The token is trained end to end, meaning it can absorb whatever statistical regularities the model needs to compensate for the absent modality, from typical entity types to the kinds of relations such entities tend to participate in.

A learnable placeholder alone, however, is a blunt instrument. The second component, structure-guided retrieval, adds a more targeted form of compensation. For each entity lacking text, the system searches among structurally similar entities that do have complete descriptions and extracts candidate textual residuals, essentially textual hints drawn from graph neighbors. The key insight, and the key caution, is that structural similarity does not guarantee that the retrieved text is actually relevant to the query at hand. Two entities may sit in similar neighborhoods for entirely different reasons. The researchers therefore treat the retrieved information as potentially useful but uncertain auxiliary evidence rather than as a trustworthy substitute for the missing description.

That caution motivates the third and arguably most important component: a guarded hierarchical probabilistic semantic adaptive calibration strategy, abbreviated HPSAC. Rather than blindly trusting retrieval-enhanced predictions, HPSAC performs validation-guided, group-specific score calibration under explicit safety constraints. Groups of queries are calibrated only when validation evidence is sufficient, and a hierarchical fallback mechanism reverts to the uncalibrated prediction whenever the evidence is weak. In experiments on the MKG-Y dataset, for example, an average of about 59 of 86 calibration groups adopted non-default configurations while roughly 27 retained the conservative fallback, showing that the mechanism applies its adjustments selectively rather than indiscriminately rewriting scores across the board.

The evaluation design is unusually thorough for this field. The researchers constructed multiple controlled missingness scenarios: nested random missingness on the MKG-W benchmark, degree-dependent missingness on MKG-Y, where text was removed from the lowest-degree entities, and relation-dependent missingness on both datasets. Under nested random missingness on MKG-W, MMA-HNS improved the mean reciprocal rank, or MRR, over the DHNS baseline by 1.4, 1.5, and 1.9 percentage points at missing rates of 10, 30, and 50 percent respectively. Under 30 percent relation-dependent missingness, the gains were 1.87 percentage points on MKG-W and 0.35 on MKG-Y. The fact that improvements grow as missingness worsens suggests the framework is doing genuine work precisely where it is needed most.

Perhaps the most scientifically interesting findings come from the ablation analysis, which dissects which components actually drive performance. The team compared a representation-only baseline, retrieval added on top, and the full model with calibration. Strikingly, neither KNN-based retrieval nor random-neighbor retrieval alone consistently improved overall MRR over the baseline, even though the KNN retrieval demonstrably found structurally more relevant neighbors, with markedly higher top-k similarity and relation overlap than random sampling. The performance gains emerged only when the calibration layer was in place. Retrieval, in other words, is informative but noisy, and its value is unlocked by reliability-controlled calibration rather than by direct injection of retrieved features.

The study also probed generalization beyond the training distribution. Models trained with only 10 percent text missingness were evaluated at 30 and 50 percent test-time missingness. All methods degraded as the distribution shift grew, but the retrieval-enhanced variants consistently outperformed the missing-text-token-only model, and the full model achieved the best overall MRR in both cross-rate settings, exceeding the baseline by 2.04 and 3.27 percentage points respectively. Sensitivity analyses showed the calibration threshold had limited effect on results, while the effect of locking missing-text groups against calibration varied by dataset, supporting its role as a conservative safeguard. Seed-level paired t-tests confirmed the improvements were statistically significant at the 0.05 level.

Why does this matter beyond the benchmarks? Knowledge graphs underpin biomedical discovery, enterprise search, and the factual grounding of large language models, and in all of these domains textual descriptions are unevenly available. Long-tail entities, from rare chemicals to newly coined products, are exactly the ones most likely to lack rich descriptions and most likely to be involved in the missing links users care about. A framework that degrades gracefully, and even improves, as text disappears moves the field closer to systems that survive contact with messy real-world data. The authors have released their code, missing-text masks, and full seed-level results in a public repository, an openness that should make replication straightforward. The deeper lesson of the work may be its discipline: when auxiliary evidence is uncertain, the winning strategy is not to trust it more, but to build a safety net that decides, query by query, how much to believe.

Subject of Research: Robust multimodal knowledge graph completion when textual entity descriptions are missing

Article Title: Robust multimodal knowledge graph completion under missing text modality

Article References: Li, S., Li, S., Pan, J., Li, Y., & Wang, P. (2026). Robust multimodal knowledge graph completion under missing text modality. International Journal of Data Science and Analytics, 22(1), Article 338. https://doi.org/10.1007/s41060-026-01315-2

Image Credits: AI Generated

DOI: 10.1007/s41060-026-01315-2

Keywords: knowledge graphs, knowledge graph completion, multimodal learning, missing modality, negative sampling, retrieval-augmented learning, machine learning, link prediction, embeddings, score calibration, MMA-HNS, data science