27,457 research outputs found
kLog: A Language for Logical and Relational Learning with Kernels
We introduce kLog, a novel approach to statistical relational learning.
Unlike standard approaches, kLog does not represent a probability distribution
directly. It is rather a language to perform kernel-based learning on
expressive logical and relational representations. kLog allows users to specify
learning problems declaratively. It builds on simple but powerful concepts:
learning from interpretations, entity/relationship data modeling, logic
programming, and deductive databases. Access by the kernel to the rich
representation is mediated by a technique we call graphicalization: the
relational representation is first transformed into a graph --- in particular,
a grounded entity/relationship diagram. Subsequently, a choice of graph kernel
defines the feature space. kLog supports mixed numerical and symbolic data, as
well as background knowledge in the form of Prolog or Datalog programs as in
inductive logic programming systems. The kLog framework can be applied to
tackle the same range of tasks that has made statistical relational learning so
popular, including classification, regression, multitask learning, and
collective classification. We also report about empirical comparisons, showing
that kLog can be either more accurate, or much faster at the same level of
accuracy, than Tilde and Alchemy. kLog is GPLv3 licensed and is available at
http://klog.dinfo.unifi.it along with tutorials
Relational Foundations For Functorial Data Migration
We study the data transformation capabilities associated with schemas that
are presented by directed multi-graphs and path equations. Unlike most
approaches which treat graph-based schemas as abbreviations for relational
schemas, we treat graph-based schemas as categories. A schema is a
finitely-presented category, and the collection of all -instances forms a
category, -inst. A functor between schemas and , which can be
generated from a visual mapping between graphs, induces three adjoint data
migration functors, -inst-inst, -inst -inst, and -inst -inst. We present an algebraic query
language FQL based on these functors, prove that FQL is closed under
composition, prove that FQL can be implemented with the
select-project-product-union relational algebra (SPCU) extended with a
key-generation operation, and prove that SPCU can be implemented with FQL
A graph-theoretic account of logics
A graph-theoretic account of logics is explored based on the general
notion of m-graph (that is, a graph where each edge can have a finite
sequence of nodes as source). Signatures, interpretation structures and
deduction systems are seen as m-graphs. After defining a category freely
generated by a m-graph, formulas and expressions in general can be seen
as morphisms. Moreover, derivations involving rule instantiation are also
morphisms. Soundness and completeness theorems are proved. As a consequence of the generality of the approach our results apply to very different
logics encompassing, among others, substructural logics as well as logics
with nondeterministic semantics, and subsume all logics endowed with an
algebraic semantics
A knowledge representation meta-model for rule-based modelling of signalling networks
The study of cellular signalling pathways and their deregulation in disease
states, such as cancer, is a large and extremely complex task. Indeed, these
systems involve many parts and processes but are studied piecewise and their
literatures and data are consequently fragmented, distributed and sometimes--at
least apparently--inconsistent. This makes it extremely difficult to build
significant explanatory models with the result that effects in these systems
that are brought about by many interacting factors are poorly understood.
The rule-based approach to modelling has shown some promise for the
representation of the highly combinatorial systems typically found in
signalling where many of the proteins are composed of multiple binding domains,
capable of simultaneous interactions, and/or peptide motifs controlled by
post-translational modifications. However, the rule-based approach requires
highly detailed information about the precise conditions for each and every
interaction which is rarely available from any one single source. Rather, these
conditions must be painstakingly inferred and curated, by hand, from
information contained in many papers--each of which contains only part of the
story.
In this paper, we introduce a graph-based meta-model, attuned to the
representation of cellular signalling networks, which aims to ease this massive
cognitive burden on the rule-based curation process. This meta-model is a
generalization of that used by Kappa and BNGL which allows for the flexible
representation of knowledge at various levels of granularity. In particular, it
allows us to deal with information which has either too little, or too much,
detail with respect to the strict rule-based meta-model. Our approach provides
a basis for the gradual aggregation of fragmented biological knowledge
extracted from the literature into an instance of the meta-model from which we
can define an automated translation into executable Kappa programs.Comment: In Proceedings DCM 2015, arXiv:1603.0053
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