255,495 research outputs found
Empowering Knowledge Bases: a Machine Learning Perspective
The construction of Knowledge Bases requires quite often
the intervention of knowledge engineering and domain experts, resulting
in a time consuming task. Alternative approaches have been developed
for building knowledge bases from existing sources of information such
as web pages and crowdsourcing; seminal examples are NELL, DBPedia,
YAGO and several others. With the goal of building very large sources of
knowledge, as recently for the case of Knowledge Graphs, even more complex
integration processes have been set up, involving multiple sources of
information, human expert intervention, crowdsourcing. Despite signi -
cant e orts for making Knowledge Graphs as comprehensive and reliable
as possible, they tend to su er of incompleteness and noise, due to the
complex building process. Nevertheless, even for highly human curated
knowledge bases, cases of incompleteness can be found, for instance with
disjointness axioms missing quite often. Machine learning methods have
been proposed with the purpose of re ning, enriching, completing and
possibly raising potential issues in existing knowledge bases while showing
the ability to cope with noise. The talk will concentrate on classes
of mostly symbol-based machine learning methods, speci cally focusing
on concept learning, rule learning and disjointness axioms learning problems,
showing how the developed methods can be exploited for enriching
existing knowledge bases. During the talk it will be highlighted as, a
key element of the illustrated solutions, is represented by the integration
of: background knowledge, deductive reasoning and the evidence coming
from the mass of the data. The last part of the talk will be devoted
to the presentation of an approach for injecting background knowledge
into numeric-based embedding models to be used for predictive tasks on
Knowledge Graphs
Report on the Workshop on Personal Knowledge Graphs (PKG 2021) at AKBC 2021
The term personal knowledge graph (PKG) has been broadly used to refer to structured representation of information about a given user, primarily in the form of entities that are personally related to the user. The potential of personal knowledge graphs as a means of managing and organizing personal data, as well as a source of background knowledge for personalizing downstream services, has recently gained increasing attention from researchers in multiple fields, including that of Information Retrieval, Natural Language Processing, and the Semantic Web. The goal of the PKG’21 workshop was to create a forum for researchers and practitioners from diverse areas to present and discuss methods, tools, techniques, and experiences related to the construction and use of personal knowledge graphs, identify open questions, and create a shared research agenda. It successfully brought about a diverse workshop program, comprising an invited keynote, paper presentations, and breakout discussions, as a half-day event at the 3rd Automated Knowledge Base Construction (AKBC’21) conference. The workshop demonstrated that while the concept and research field of personal knowledge graphs is still in its early stages, there are many promising avenues of future development and research that already, and independently, have attracted the interest of several different communities.publishedVersio
Substructure Discovery Using Minimum Description Length and Background Knowledge
The ability to identify interesting and repetitive substructures is an
essential component to discovering knowledge in structural data. We describe a
new version of our SUBDUE substructure discovery system based on the minimum
description length principle. The SUBDUE system discovers substructures that
compress the original data and represent structural concepts in the data. By
replacing previously-discovered substructures in the data, multiple passes of
SUBDUE produce a hierarchical description of the structural regularities in the
data. SUBDUE uses a computationally-bounded inexact graph match that identifies
similar, but not identical, instances of a substructure and finds an
approximate measure of closeness of two substructures when under computational
constraints. In addition to the minimum description length principle, other
background knowledge can be used by SUBDUE to guide the search towards more
appropriate substructures. Experiments in a variety of domains demonstrate
SUBDUE's ability to find substructures capable of compressing the original data
and to discover structural concepts important to the domain. Description of
Online Appendix: This is a compressed tar file containing the SUBDUE discovery
system, written in C. The program accepts as input databases represented in
graph form, and will output discovered substructures with their corresponding
value.Comment: See http://www.jair.org/ for an online appendix and other files
accompanying this articl
Information extraction
In this paper we present a new approach to extract relevant information by knowledge graphs from natural language text. We give a multiple level model based on knowledge graphs for describing template information, and investigate the concept of partial structural parsing. Moreover, we point out that expansion of concepts plays an important role in thinking, so we study the expansion of knowledge graphs to use context information for reasoning and merging of templates
Investigating the use of background knowledge for assessing the relevance of statements to an ontology in ontology evolution
The tasks of learning and enriching ontologies with new concepts and relations have attracted a lot of attention in the research community, leading to a number of tools facilitating the process of building and updating ontologies. These tools often discover new elements of information to be included in the considered ontology from external data sources such as text documents or databases, transforming these elements into ontology compatible statements or axioms. While some techniques are used to make sure that statements to be added are compatible with the ontology (e.g. through conflict detection), such tools generally pay little attention to the relevance of the statement in question. It is either assumed that any statement extracted from a data source is relevant, or that the user will assess whether a statement adds value to the ontology. In this paper, we investigate the use of background knowledge about the context where statements appear to assess their relevance. We devise a methodology to extract such a context from ontologies available online, to map it to the considered ontology and to visualize this mapping in a way that allows to study the intersection and complementarity of the two sources of knowledge. By applying this methodology on several examples, we identified an initial set of patterns giving strong indications concerning the relevance of a statement, as well as interesting issues to be considered when applying such techniques
Using Description Logics for Recognising Textual Entailment
The aim of this paper is to show how we can handle the Recognising Textual
Entailment (RTE) task by using Description Logics (DLs). To do this, we propose
a representation of natural language semantics in DLs inspired by existing
representations in first-order logic. But our most significant contribution is
the definition of two novel inference tasks: A-Box saturation and subgraph
detection which are crucial for our approach to RTE
25 years development of knowledge graph theory: the results and the challenge
The project on knowledge graph theory was begun in 1982. At the initial stage, the goal was to use graphs to represent knowledge in the form of an expert system. By the end of the 80's expert systems in medical and social science were developed successfully using knowledge graph theory. In the following stage, the goal of the project was broadened to represent natural language by knowledge graphs. Since then, this theory can be considered as one of the methods to deal with natural language processing. At the present time knowledge graph representation has been proven to be a method that is language independent. The theory can be applied to represent almost any characteristic feature in various languages.\ud
The objective of the paper is to summarize the results of 25 years of development of knowledge graph theory and to point out some challenges to be dealt with in the next stage of the development of the theory. The paper will give some highlight on the difference between this theory and other theories like that of conceptual graphs which has been developed and presented by Sowa in 1984 and other theories like that of formal concept analysis by Wille or semantic networks
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