1,999 research outputs found
Context-Free Path Querying with Structural Representation of Result
Graph data model and graph databases are very popular in various areas such
as bioinformatics, semantic web, and social networks. One specific problem in
the area is a path querying with constraints formulated in terms of formal
grammars. The query in this approach is written as grammar, and paths querying
is graph parsing with respect to given grammar. There are several solutions to
it, but how to provide structural representation of query result which is
practical for answer processing and debugging is still an open problem. In this
paper we propose a graph parsing technique which allows one to build such
representation with respect to given grammar in polynomial time and space for
arbitrary context-free grammar and graph. Proposed algorithm is based on
generalized LL parsing algorithm, while previous solutions are based mostly on
CYK or Earley algorithms, which reduces time complexity in some cases.Comment: Evaluation extende
Comparing and evaluating extended Lambek calculi
Lambeks Syntactic Calculus, commonly referred to as the Lambek calculus, was
innovative in many ways, notably as a precursor of linear logic. But it also
showed that we could treat our grammatical framework as a logic (as opposed to
a logical theory). However, though it was successful in giving at least a basic
treatment of many linguistic phenomena, it was also clear that a slightly more
expressive logical calculus was needed for many other cases. Therefore, many
extensions and variants of the Lambek calculus have been proposed, since the
eighties and up until the present day. As a result, there is now a large class
of calculi, each with its own empirical successes and theoretical results, but
also each with its own logical primitives. This raises the question: how do we
compare and evaluate these different logical formalisms? To answer this
question, I present two unifying frameworks for these extended Lambek calculi.
Both are proof net calculi with graph contraction criteria. The first calculus
is a very general system: you specify the structure of your sequents and it
gives you the connectives and contractions which correspond to it. The calculus
can be extended with structural rules, which translate directly into graph
rewrite rules. The second calculus is first-order (multiplicative
intuitionistic) linear logic, which turns out to have several other,
independently proposed extensions of the Lambek calculus as fragments. I will
illustrate the use of each calculus in building bridges between analyses
proposed in different frameworks, in highlighting differences and in helping to
identify problems.Comment: Empirical advances in categorial grammars, Aug 2015, Barcelona,
Spain. 201
Parameter Learning of Logic Programs for Symbolic-Statistical Modeling
We propose a logical/mathematical framework for statistical parameter
learning of parameterized logic programs, i.e. definite clause programs
containing probabilistic facts with a parameterized distribution. It extends
the traditional least Herbrand model semantics in logic programming to
distribution semantics, possible world semantics with a probability
distribution which is unconditionally applicable to arbitrary logic programs
including ones for HMMs, PCFGs and Bayesian networks. We also propose a new EM
algorithm, the graphical EM algorithm, that runs for a class of parameterized
logic programs representing sequential decision processes where each decision
is exclusive and independent. It runs on a new data structure called support
graphs describing the logical relationship between observations and their
explanations, and learns parameters by computing inside and outside probability
generalized for logic programs. The complexity analysis shows that when
combined with OLDT search for all explanations for observations, the graphical
EM algorithm, despite its generality, has the same time complexity as existing
EM algorithms, i.e. the Baum-Welch algorithm for HMMs, the Inside-Outside
algorithm for PCFGs, and the one for singly connected Bayesian networks that
have been developed independently in each research field. Learning experiments
with PCFGs using two corpora of moderate size indicate that the graphical EM
algorithm can significantly outperform the Inside-Outside algorithm
Pattern matching in compilers
In this thesis we develop tools for effective and flexible pattern matching.
We introduce a new pattern matching system called amethyst. Amethyst is not
only a generator of parsers of programming languages, but can also serve as an
alternative to tools for matching regular expressions.
Our framework also produces dynamic parsers. Its intended use is in the
context of IDE (accurate syntax highlighting and error detection on the fly).
Amethyst offers pattern matching of general data structures. This makes it a
useful tool for implementing compiler optimizations such as constant folding,
instruction scheduling, and dataflow analysis in general.
The parsers produced are essentially top-down parsers. Linear time complexity
is obtained by introducing the novel notion of structured grammars and
regularized regular expressions. Amethyst uses techniques known from compiler
optimizations to produce effective parsers.Comment: master thesi
Rascal: From Algebraic Specification to Meta-Programming
Algebraic specification has a long tradition in bridging the gap between
specification and programming by making specifications executable. Building on
extensive experience in designing, implementing and using specification
formalisms that are based on algebraic specification and term rewriting (namely
Asf and Asf+Sdf), we are now focusing on using the best concepts from algebraic
specification and integrating these into a new programming language: Rascal.
This language is easy to learn by non-experts but is also scalable to very
large meta-programming applications.
We explain the algebraic roots of Rascal and its main application areas:
software analysis, software transformation, and design and implementation of
domain-specific languages. Some example applications in the domain of
Model-Driven Engineering (MDE) are described to illustrate this.Comment: In Proceedings AMMSE 2011, arXiv:1106.596
Maude: specification and programming in rewriting logic
Maude is a high-level language and a high-performance system supporting executable specification and declarative programming in rewriting logic. Since rewriting logic contains equational logic, Maude also supports equational specification and programming in its sublanguage of functional modules and theories. The underlying equational logic chosen for Maude is membership equational logic, that has sorts, subsorts, operator overloading, and partiality definable by membership and equality conditions. Rewriting logic is reflective, in the sense of being able to express its own metalevel at the object level. Reflection is systematically exploited in Maude endowing the language with powerful metaprogramming capabilities, including both user-definable module operations and declarative strategies to guide the deduction process. This paper explains and illustrates with examples the main concepts of Maude's language design, including its underlying logic, functional, system and object-oriented modules, as well as parameterized modules, theories, and views. We also explain how Maude supports reflection, metaprogramming and internal strategies. The paper outlines the principles underlying the Maude system implementation, including its semicompilation techniques. We conclude with some remarks about applications, work on a formal environment for Maude, and a mobile language extension of Maude
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