In the modern data-driven world, answering queries over heterogeneous and semantically inconsistent data remains a significant challenge. Modern datasets originate from diverse sources, such as relational databases, semi-structured repositories, and unstructured documents, leading to substantial variability in schemas, terminologies, and data formats. Traditional systems, constrained by rigid syntactic matching and strict data binding, struggle to capture critical semantic connections and schema ambiguities, failing to meet the growing demand among data scientists for advanced forms of flexibility and context-awareness in query answering. In parallel, the advent of Large Language Models (LLMs) has introduced new capabilities in natural language interpretation, making them highly promising for addressing such challenges. However, LLMs alone lack the systematic rigor and explainability required for robust query processing and decision-making in high-stakes domains. In this paper, we propose Soft Query Answering (Soft QA), a novel hybrid approach that integrates LLMs as an intermediate semantic layer within the query processing pipeline. Soft QA enhances query answering adaptability and flexibility by injecting semantic understanding through context-aware, schema-informed prompts, and leverages LLMs to semantically link entities, resolve ambiguities, and deliver accurate query results in complex settings. We demonstrate its practical effectiveness through real-world examples, highlighting its ability to resolve semantic mismatches and improve query outcomes without requiring extensive data cleaning or restructuring.

Deductive rules over graph data are a commonly accepted way to address complex reasoning tasks; among them, we mention the company control problem, which consists of determining who exercises control - directly or indirectly, through aggregation and recursion - over ownership graphs. Solving this and similar problems is crucial for the Central Bank of Italy; the Bank uses Vadalog, a state-of-the-art proprietary reasoner based on an extended Datalog, to routinely manage changes (insertions and deletions) of ownership in large graphs covering all Italian companies. However, at a smaller scale, similar activities are also relevant in more targeted activities, e.g., for financial intelligence tasks in the public and private sectors. In this paper, we present a general scheme for generating active rules that correctly handle recursion, aggregation, and stratified negation, so as to deploy reactive reasoners over graph data managers. We show how to convert high-level reasoning rules expressed in Datalog into triggers as Cypher statements, the most aligned language with the recently standardized Graph Query Language. We discuss how Cypher triggers can be managed by a dedicated controller that replicates the reasoning capabilities of a deductive reasoner engine within a graph database system. We implement the controller within Neo4j, the most widespread open-source graph database, demonstrating that our implementation achieves adequate performance over small-to-medium property graphs. We also show that our approach is general and applicable to other domains (e.g., laws), directly allowing reasoning with deductive rules over graph databases. Finally, we discuss how the translation process from Datalog to Cypher can be facilitated by state-of-the-art pre-trained Large Language Models, capable of accurately performing the translation task.

Languages, namely, fragments, of the Datalog+/- family are attracting interest in both academia and industry because of their possibility to balance high expressive power and computational complexity. However, understanding the differences among the fragments, mastering them to achieve scalable industrial applications, and communicating their peculiarities to a non-expert audience is challenging for researchers, developers, logicians, and educators. In this demo, we introduce Vadacode, an IDE for Datalog+/- designed to support a broad category of users. The tool offers advanced features, including fragment detection, syntax highlighting, code completion, error diagnostics, schema inference, debugging support, and AI-assisted coding capabilities. Thanks to our experience in the financial context, our demo will guide the audience in modeling financial Datalog+/- programs, showcasing a seamless and effective coding experience.

Over the past years, there has been a growing demand for ontological reasoning systems based on languages of the Datalog+/- family, such as Vadalog, for their ability to effectively model a wide range of real-world problems with powerful features such as existential quantification. As the scale and complexity of data analysis tasks continue to grow, the ability to distribute the computational workload across multiple non-communicating processors has become vital for these systems to achieve scalable performance. The joint presence of existential quantification and recursion poses new challenges, currently unsolved by existing distributed systems, which only concentrate on Datalog and are therefore unsuitable for ontological reasoning. When working across multiple processors, generating all the facts to answer a specific reasoning query, avoiding duplication, and guaranteeing termination are non-trivial tasks as infinitely many new symbols and facts can be generated by existential quantification and recursion. In this paper, we address such challenges and introduce the first distributed framework in the Datalog+/- space. We propose the condition of homomorphic decomposability, which identifies sets of Datalog+/- rules with good distribution properties. We put homomorphic decomposability into action with a distributed reasoning algorithm for Warded Datalog+/-, the core of Vadalog. We implement Vadalog Parallel, a distributed reasoner for Vadalog and provide experimental evaluation against state-of-the-art systems.

The Company Control Problem consists in understanding who exerts decision power in companies. Central banks, financial intelligence units, and market regulators are all interested in this problem, which is crucial for their core goals. In the context where these actors operate, changes in company control call for immediate reactions.Yet, computing control relationships is a computationally expensive problem that involves traversing the entire shareholding structure and aggregating shares over multiple paths.In the context of the joint European banking supervision, the Bank of Italy will soon handle the shareholding graph of all European companies, which comprises hundreds of millions of entities (firms and individuals) and billions of edges and properties. This graph is highly volatile as the Bank continuously receives updates about shareholding relationships with unpredictable high frequency. This makes the straightforward bulk solution, where all the company control relationships are computed and materialized whenever a change occurs, unaffordable in practice.In this work, we present an incremental rule-based formalization of the problem, adopting the Vadalog fragment of the Datalog+/- families of languages. Our approach analyzes the specific change, singles out the portions of the graph that are affected by it, and selectively updates them. This allows one both to timely evaluate the impact of ownership variations on an extensive European-scale shareholding graph and to enable economists to perform the so-called "what-if analysis", i.e., simulation scenarios to proactively study the consequences of potential share acquisition operations, that currently are prohibitively time expensive. We provide an extensive experimental evaluation on very large company graphs, comparatively confirming the scalability of our technique in a real production setting.

Logic-based Knowledge Graphs (KGs) are gaining momentum in academia and industry thanks to the rise of expressive and efficient languages for Knowledge Representation and Reasoning (KRR). These languages accurately express business rules, through which valuable new knowledge is derived. A versatile and scalable backend reasoner, like Vadalog, a state-of-the-art system for logic-based KGs---based on an extension of Datalog---executes the reasoning. In this demo, we present KG-Roar, a web-based interactive development and navigation environment for logical KGs. The system lets the user augment an input graph database with intensional definitions of new nodes and edges and turn it into a KG, via the metaphor of reasoning widgets---user-defined or off-the-shelf code snippets that capture business definitions in the Vadalog language. Then, the user can seamlessly browse the original and the derived nodes and edges within a "Virtual Knowledge Graph", which is reasoned upon and generated interactively at runtime, thanks to the scalability and responsiveness of Vadalog. KG-Roar is domain-independent but domain aware, as exploration controls are contextually generated based on the intensional definitions. We walk the audience through KG-Roar showcasing the construction of certain business definitions and putting it into action on a real-world financial KG, from our work with the Bank of Italy.

DatalogMTL is an extension of the fundamental rule language Datalog with metric temporal operators over rational numbers, whose adoption is soaring within an increasing number of communities (semantic web, databases, stream data processing, temporal logic, knowledge graphs, etc.), which are more and more willing to handle temporal data and deal with temporal database queries as a consequence. Despite the rising research efforts towards new extensions of DatalogMTL, such as the fundamental support for aggregations, and the uprising systems, we still lack a corpus of benchmarks for temporal reasoning. This paper contributes iTemporal, an extensible generator of temporal benchmarks. Our system is able to generate a very broad set of benchmarks, thanks to a white-box configuration mechanism to control and stimulate the theoretical underpinnings of DatalogMTL and its extensions, such as temporal operators in the presence of full recursion and aggregations. We provide a comprehensive presentation of the system as well as an empirical evaluation of the benchmarks within two reference reasoners.

Equality-generating dependencies (EGDs) allow to fully exploit the power of existential quantification in ontological reasoning settings modeled via Tuple-Generating Dependencies (TGDs), by enabling value-assignment or forcing the equivalence of fresh symbols. These capabilities are at the core of many common reasoning tasks, including graph traversals, clustering, data matching and data fusion, and many more related real-world scenarios. However, the interplay of TGDs and EGDs is known to lead to undecidability or intractability of query answering in tractable Datalog+/- fragments, like Warded Datalog+/-, for which, in the sole presence of TGDs, query answering is PTIME in data complexity. Restrictions of equality constraints, like separable EGDs, have been studied, but all achieve decidability at the cost of limited expressive power, which makes them unsuitable for the mentioned tasks. This paper introduces the class of "harmless" EGDs, that subsume separable EGDs and allow to model a very broad class of tasks. We contribute a sufficient syntactic condition for testing harmlessness, an undecidable task in general. We argue that in Warded Datalog+/- with harmless EGDs, ontological reasoning is decidable and PTIME. From such theoretical underpinnings, we develop novel chase-based techniques for reasoning with harmless EGDs and present an implementation within the Vadalog system, a state-of-the-art Datalog-based reasoner. We provide full-scale experimental evaluation and comparative analysis.

The Company Control Problem is of central importance to banks, financial intermediaries, financial intelligence units, regulatory and supervisory authorities such as the Central Banks. It consists in understanding who takes decisions in a large company network, that is, who controls the majority of votes for each single company. This has an impact on a large number of business areas, with examples including evaluation of creditworthiness, economic analysis of the control dispersion, anti-money laundering, prevention of potentially hostile takeovers, evaluation of risks, and shock propagation.This paper is based on our experience with the Central Bank of Italy and presents an approach to the solution of the company control problem in distributed settings, especially relevant, as large and distributed ownership graphs reflect European-size applications where scalability is paramount.In particular, we formalize the problem as query answering on a large distributed database. We study how independent subqueries can be executed in each partition and the partial results assembled at a master site to produce the answer. We study the formal properties of the problem, that is not easily parallelizable, and then present a method that supports parallelism at best.We present a thorough experimental evaluation of our approach with the Italian company graph of the Bank of Italy and the European Register of Financial Intermediaries and Affiliates as well as many artificial graphs to fully assess scalability.

Motivated by our experience in building the Enterprise Knowledge Graph of Italian companies for the Central Bank of Italy, in this paper we present an in-depth case analysis of company ownership graphs, graphs having company ownership as a central concept. In particular, we study and introduce three industrially relevant problems related to such graphs: company control, asset eligibility and detection of personal links. We formally characterize the problems and present Vada-Link, a framework based on state-of-the-art approaches for knowledge representation and reasoning. With our methodology and system, we solve the problems at hand in a scalable, model-independent and generalizable way. We illustrate the favourable architectural properties of Vada-Link and give experimental evaluation of the approach.

Adopting a mature AI strategy is fundamental for modern knowledge companies to govern the proliferation of smart AI-driven applications and to coordinate them within coherent knowledge workflows. We propose knowledge graphs as the reference technology for the enterprise AI context, i.e., the complex of entities, properties and relationships that shape a business domain and constitute a common backbone for all AI-driven applications. We contribute and discuss principles to design software architectures for AI-driven applications based on knowledge graphs. We focus on the Vadalog system, a successful knowledge graph middleware from the University of Oxford and show knowledge graphs in action in a number of use cases from the financial domain.

The definition of mappings between heterogeneous schemas is a critical activity of any database application. Existing tools provide high level interfaces for the discovery of correspondences between elements of schemas, but schema mappings need to be manually specified every time from scratch, even if the scenario at hand is similar to one that has already been addressed. The problem is that schema mappings are precisely defined over a pair of schemas and cannot directly be reused on different scenarios. We tackle this challenge by generalizing schema mappings as meta-mappings: formalisms that describe transformations between generic data structures called meta-schemas. We formally characterize schema mapping reuse and explain how meta-mappings are able to: (i) capture enterprise knowledge from previously defined schema mappings and (ii) use this knowledge to suggest new mappings. We develop techniques to infer meta-mappings from existing mappings, to organize them into a searchable repository, and to leverage the repository to propose to users mappings suitable for their needs. We study effectiveness and efficiency in an extensive evaluation over real-world scenarios and show that our system can infer, store, and search millions of meta-mappings in seconds.

Over the past years, there has been a resurgence of Datalog-based systems in the database community as well as in industry. In this context, it has been recognized that to handle the complex knowledge-based scenarios encountered today, such as reasoning over large knowledge graphs, Datalog has to be extended with features such as existential quantification. Yet, Datalog-based reasoning in the presence of existential quantification is in general undecidable. Many efforts have been made to define decidable fragments. Warded Datalog+/- is a very promising one, as it captures PTIME complexity while allowing ontological reasoning. Yet so far, no implementation of Warded Datalog+/- was available. In this paper we present the Vadalog system, a Datalog-based system for performing complex logic reasoning tasks, such as those required in advanced knowledge graphs. The Vadalog system is Oxford's contribution to the VADA research programme, a joint effort of the universities of Oxford, Manchester and Edinburgh and around 20 industrial partners. As the main contribution of this paper, we illustrate the first implementation of Warded Datalog+/-, a high-performance Datalog+/- system utilizing an aggressive termination control strategy. We also provide a comprehensive experimental evaluation.

Data processing is the core of any statistical information system. Statisticians are interested in specifying transformations and manipulations of data at a high level, in terms of entities of statistical models such as time series. We illustrate here an experience at the Bank of Italy where (i) a language, EXL, has been defined for the declarative specification of statistical programs, (ii) an approach for the translation of EXL code into executables in various target systems has been developed, and (iii) a concrete implementation, EXLEngine, has been carried out. The approach leverages on schema mappings as an intermediate specification step, in order to facilitate the translation from EXL towards several target systems.

A runtime approach to model-generic translation of schema and data is proposed.