# Actively Learning Concepts and Conjunctive Queries under ELr-Ontologies

arXiv: https://arxiv.org/abs/2105.08326 · HTML: https://mlsanity.com/paper/2105.08326/

## Key facts

- Cited by 3 papers in the map (data through 14 Oct 2026).
- Builds on 4 of its 45 references that are in the map.
- First posted on arXiv 18 May 2021.

## Builds on (most cited first, 4 of 4)

- [Learning Description Logic Ontologies. Five Approaches. Where Do They Stand?](https://mlsanity.com/paper/2104.01193/) (2021)
- [Exact Learning of Lightweight Description Logic Ontologies](https://mlsanity.com/paper/1709.07314/) (2017)
- [Conjunctive Queries: Unique Characterizations and Exact Learnability](https://mlsanity.com/paper/2008.06824/) (2020)
- [Learning Query Inseparable ELH Ontologies](https://mlsanity.com/paper/1911.07229/) (2019)

## Built on by (most cited first, 3 of 3)

- [From Subsumption to Satisfiability: LLM-Assisted Active Learning for OWL Ontologies](https://mlsanity.com/paper/2604.16672/) (2026)
- [Unique Characterisability and Learnability of Temporal Queries Mediated by an Ontology](https://mlsanity.com/paper/2306.07662/) (2023)
- [Model Change for Description Logic Concepts](https://mlsanity.com/paper/2603.05562/) (2026)

## Abstract (arXiv)

We consider the problem to learn a concept or a query in the presence of an ontology formulated in the description logic ELr, in Angluin's framework of active learning that allows the learning algorithm to interactively query an oracle (such as a domain expert). We show that the following can be learned in polynomial time: (1) EL-concepts, (2) symmetry-free ELI-concepts, and (3) conjunctive queries (CQs) that are chordal, symmetry-free, and of bounded arity. In all cases, the learner can pose to the oracle membership queries based on ABoxes and equivalence queries that ask whether a given concept/query from the considered class is equivalent to the target. The restriction to bounded arity in (3) can be removed when we admit unrestricted CQs in equivalence queries. We also show that EL-concepts are not polynomial query learnable in the presence of ELI-ontologies.