Senior Software Engineer, Ontology & Reasoning Systems (819)

New York · 5+ years experience · Full-time · Hybrid · Posted Oct 14, 2026

At a glance

Protegrity is seeking a Senior Software Engineer, Ontology & Reasoning Systems to design and build the ontology and reasoning layer connecting structured sources, semi-structured metadata, and unstructured documents.
You will formalize complex domains into entities, relationships, constraints, and rules to allow the system to derive conclusions from underlying facts while ensuring explainability and traceability.
The role requires working closely with product and research teams to define formal models, improve reasoning quality, and build production services that support accurate, reviewable outputs.

Own the ontology and rule layer that unifies structured, semi-structured, and unstructured enterprise data into a single reasoning model.
Model entities, relationships, events, and constraints across heterogeneous sources, and develop rules that derive conclusions from combinations of facts.
Use LLMs at the ingestion boundary for extraction, normalization, and categorization, with appropriate validation of model-generated outputs.
Make system findings traceable by connecting each conclusion to the source facts and rules that produced it.
Build retrieval capabilities, including vector search, keyword search, and graph traversal, to support reasoning workflows.
Improve quality through entity resolution, constraint modeling, and structured handling of conflicting or overlapping sources.
Ship production services and research prototypes with a focus on correctness, reliability, and maintainability.

5+ years of experience building backend systems in a modern language such as Python, Go, Java, Scala, Rust, or similar, or equivalent practical experience.
A strong formal and mathematical foundation, including discrete mathematics, logic, and graph theory.
The ability to reason about soundness, completeness, and tractability, and to express complex domains as formal rules and constraints.
Hands-on experience with declarative, logic-based, or rule-based reasoning systems such as Datalog, Answer Set Programming, constraint logic programming, Prolog, production rule engines, SMT solvers, or similar.
Practical experience building LLM-powered systems, including structured extraction, RAG, or classification pipelines, with sound judgment about where model outputs require validation.
Deep experience with knowledge graphs and graph data, including RDF, SPARQL, property graphs, or graph databases such as Neo4j.
Experience designing systems whose outputs trace back to their inputs, including provenance, derivation chains, or evidence trails.
Strong debugging, testing, and validation practices, with attention to correctness.

Experience with constraint satisfaction or deductive reasoning, including CSP, unification, fixpoint or closure computation, or constraint propagation.
Experience with formal ontology and semantics, including OWL, SHACL, description logics, or reasoners.
Experience with LLM evaluation, entity resolution, citation validation, or hallucination reduction.
Experience with symbolic computation, theorem proving, model checking, or formal verification.

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