Unified representations for data that span relational, document, graph and other models. The MM-cat line uses category-theoretic abstractions to express schemas and transformations independently of a concrete DBMS.

• 2022A unified representation and transformation of multi‐model data using category theory
• 2021Categorical Modeling of Multi-Model Data: One Model to Rule Them All

Inference of implicit schemas, identifiers, references, redundancy, and integrity constraints from heterogeneous data. MM-infer focuses on common multi-model schema inference; FDepHunter studies reliable functional-dependency discovery using negative examples and human feedback.

• 2025FDepHunter: Harnessing Negative Examples to Expose Fakes and Reveal Ghosts
• 2022A Universal Approach for Multi-Model Schema Inference
• 2022Schema Inference for Multi-Model Data
• 2022A Comparative Analysis of JSON Schema Inference Algorithms.

Propagation of structural changes through stored data, mappings, application queries and persistence code. MM-evocat handles model-independent data evolution, MM-evoque synchronises queries, while ORMorpher extends the idea to application persistence frameworks.

• 2025ORMorpher: An Interactive Framework for ORM Translation and Optimization
• 2025Model-Agnostic Evolution Management
• 2024Modelling and Evolution Management of Multi-Model Data
• 2024MM-evoque: Query Synchronisation in Multi-Model Databases

Querying across heterogeneous models and languages while preserving semantics. MM-quecat provides a unified query layer and DortDB composes familiar native query languages over multi-model data ponds using a shared algebra.

• 2025DortDB: Bridging Query Languages for Multi-Model Data Ponds
• 2024A Universal Approach for Simplified Redundancy-Aware Cross-Model Querying
• 2023MM-quecat: A Tool for Unified Querying of Multi-Model Data

Automated selection of representations, mappings and indexes using workloads and empirical performance evidence. MM-mapsearch explores alternative multi-model mappings and estimates their performance; related work studies index selection and DBMS choice.

• 2026MM-mapsearch: Workload-Aware Mapping Selection
• 2026Refining storage strategy through index selection methods in multi-model database systems: A survey
• 2025SQL vs NoSQL: Six Systems Compared