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TreeBased Picture Generation
 Theoretical Computer Science
, 2000
"... . The concept of treebased picture generation is introduced. It is shown that there are equivalent treebased definitions of four picturegenerating devices known from the literature, namely collage grammars, mutually recursive function systems, contextfree chaincode grammars, and 0Lsystems with ..."
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. The concept of treebased picture generation is introduced. It is shown that there are equivalent treebased definitions of four picturegenerating devices known from the literature, namely collage grammars, mutually recursive function systems, contextfree chaincode grammars, and 0Lsystems with turtle interpretation. Furthermore, generalisations of each of these systems are discussed. 1 Introduction During the last two decades picture generation has become a large field whose manyfold aspects are studied in mathematics as well as in practical and theoretical computer science. It attracts the interest of numerous researchers from diverse directions, which is no surprise because one can find in this area a great number of intellectually appealing mathematical and computational problems, interesting applications like the modelling of plant development and, one should not forget to mention this, an astonishing variety of beautiful pictures. In this paper picture generation is studied...
Relating Accumulative and NonAccumulative Functional Programs
 In Rewriting Techniques and Applications, Proceedings, volume 2051 of LNCS
, 2001
"... We study the problem to transform functional programs, which intensively use append functions (like inefficient list reversal), into programs, which use accumulating parameters instead (like efficient list reversal). We give an (automatic) transformation algorithm for our problem and identify a clas ..."
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Cited by 14 (6 self)
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We study the problem to transform functional programs, which intensively use append functions (like inefficient list reversal), into programs, which use accumulating parameters instead (like efficient list reversal). We give an (automatic) transformation algorithm for our problem and identify a class of functional programs, namely restricted 2modular tree transducers, to which it can be applied. Moreover, since we get macro tree transducers as transformation result and since we also give the inverse transformation algorithm, we have a new characterization for the class of functions induced by macro tree transducers.
Learning ktestable tree sets from positive data
, 1993
"... A kTestable tree set in the Strict sense (kTS) is essentially defined by a finite set of patterns of "size " k that are permitted to appear in the trees of the tree language. Given a positive sample S of trees over a ranked alphabet, an algorithm is proposed which obtains the sma ..."
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A kTestable tree set in the Strict sense (kTS) is essentially defined by a finite set of patterns of &quot;size &quot; k that are permitted to appear in the trees of the tree language. Given a positive sample S of trees over a ranked alphabet, an algorithm is proposed which obtains the smallest kTS tree set containing S. The proposed algorithm is polynomial on the size of S and identifies the class of kTS tree languages in the limit from positive data. I.
Semantic Parsing with Bayesian Tree Transducers
"... Many semantic parsing models use tree transformations to map between natural language and meaning representation. However, while tree transformations are central to several stateoftheart approaches, little use has been made of the rich literature on tree automata. This paper makes the connection ..."
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Cited by 10 (1 self)
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Many semantic parsing models use tree transformations to map between natural language and meaning representation. However, while tree transformations are central to several stateoftheart approaches, little use has been made of the rich literature on tree automata. This paper makes the connection concrete with a tree transducer based semantic parsing model and suggests that other models can be interpreted in a similar framework, increasing the generality of their contributions. In particular, this paper further introduces a variational Bayesian inference algorithm that is applicable to a wide class of tree transducers, producing stateoftheart semantic parsing results while remaining applicable to any domain employing probabilistic tree transducers. 1
TREEBAG  A TreeBased Generator for Objects of Various Types
 Bericht Nr. 1/98, Universitat Bremen, Fachbereich Mathematik und Informatik
, 1998
"... . A software system called TreebagTreeBased Generatoris presented. The aim behind Treebag is to allow for the generation and visualization of objects of all kinds: pictures, trees, graphs, strings, numbers, etc. The basic principle is that tree generators like, for instance, regular tree gram ..."
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Cited by 9 (4 self)
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. A software system called TreebagTreeBased Generatoris presented. The aim behind Treebag is to allow for the generation and visualization of objects of all kinds: pictures, trees, graphs, strings, numbers, etc. The basic principle is that tree generators like, for instance, regular tree grammars, generate terms over symbols that are interpreted by appropriate algebras as operations on the domain of objects under consideration. Thus, every term is viewed as an expression that denotes one of the objects of interest. These objects can be visualized using appropriate displays. 1 Introduction In mathematics and computer science, one of the most natural and universal ways to denote elements of a given data space is to use expressions over a suitable set of operations, like p 3=7 + 5. The usefulness of this concept is even strengthened by the fact that such an expression may contain variablesin which case it does not denote a particular, single object, but a set of objects or a ...
Tree Transducer Composition as Deforestation Method for Functional Programs
, 2001
"... We demonstrate that composition techniques for tree transducers are suitable to eliminate intermediate results in functional programs. We consider two composition techniques, which view special functional programs as (restricted) macro tree transducers: The first uses composition techniques for macr ..."
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Cited by 8 (2 self)
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We demonstrate that composition techniques for tree transducers are suitable to eliminate intermediate results in functional programs. We consider two composition techniques, which view special functional programs as (restricted) macro tree transducers: The first uses composition techniques for macro tree transducers directly. The second is indirect in that it (i) translates macro tree transducers into attributed tree transducers, (ii) uses a composition technique for attributed tree transducers, and (iii) translates the composition result back into a macro tree transducer. We informally compare these techniques with the deforestation technique of Wadler. In particular we show that the composition techniques eliminate intermediate results for certain kinds of function definitions, for which classical deforestation fails.
Formal Efficiency Analysis for Tree Transducer Composition
, 2004
"... We study the question of efficiency improvement or deterioration for a semanticspreserving program transformation technique for (lazy) functional languages, based on composition of restricted macro tree transducers. By annotating programs to reflect the intensional property ``computation time' ..."
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Cited by 7 (1 self)
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We study the question of efficiency improvement or deterioration for a semanticspreserving program transformation technique for (lazy) functional languages, based on composition of restricted macro tree transducers. By annotating programs to reflect the intensional property ``computation time'' explicitly in the computed output and by manipulating such annotations, we formally prove syntactic conditions under which the composed program is guaranteed to be not less efficient than the original program with respect to the number of callbyname reduction steps required to reach normal form. Under additional conditions the guarantee also holds for callbyneed semantics. The criteria developed can be checked automatically and efficiently, and thus are suitable for integration into an optimizing compiler.
A Pumping Lemma for Output Languages of Macro Tree Transducers
"... The concept of macro tree transducer is a formal model for studying properties of syntaxdirected translations and of functional languages which are based on primitive recursion. In this paper, for output languages of producing and nondeleting macro tree transducers, we introduce and prove a pumping ..."
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Cited by 7 (1 self)
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The concept of macro tree transducer is a formal model for studying properties of syntaxdirected translations and of functional languages which are based on primitive recursion. In this paper, for output languages of producing and nondeleting macro tree transducers, we introduce and prove a pumping lemma. We apply this pumping lemma to gain two results: (1) there is no producing and nondeleting macro tree transducer which computes the set of all monadic trees with double exponential height as output and (2) there are hierarchies of producing and nondeleting macro tree transducers with respect to their number of functions.
A Characterization of the Sets of Hypertrees Generated by HyperedgeReplacement Graph Grammars
 Theory of Computing Systems
, 1997
"... . A characterization of the sets of hypertrees generated by hyperedgereplacement graph grammars is given. The characterization says that these sets are exactly those which have the form val(T ), where T , a set of terms over hyperedgereplacement operations, is the output language of a finitecopying ..."
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Cited by 7 (2 self)
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. A characterization of the sets of hypertrees generated by hyperedgereplacement graph grammars is given. The characterization says that these sets are exactly those which have the form val(T ), where T , a set of terms over hyperedgereplacement operations, is the output language of a finitecopying topdown tree transducer. Furthermore, the terms in T may be required to consist of hyperedgereplacement operations whose underlying hypergraphs are hypertrees. The result is closely related to a similar characterization that was obtained for the case of string graphs by Engelfriet and Heyker some years ago. In fact, the results of this paper also yield a new proof for the characterization by Engelfriet and Heyker. 1 Introduction Hyperedgereplacement graph grammars, also called contextfree hypergraph grammars, are wellstudied devices for the generation of graph and hypergraph languages (see, e.g., [Hab92, Eng97, DHK97]). Their basic operation is the replacement of a nonterminal hypered...
The Equivalence of BottomUp and TopDown TreetoGraph Transducers
 J. COMPUT. SYST. SCI
, 1996
"... We introduce the bottomup treetograph transducer, which is very similar to the usual (total deterministic) bottomup tree transducer except that it translates trees into hypergraphs rather than trees, using hypergraph substitution instead of tree substitution. If every output hypergraph of the tr ..."
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Cited by 7 (4 self)
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We introduce the bottomup treetograph transducer, which is very similar to the usual (total deterministic) bottomup tree transducer except that it translates trees into hypergraphs rather than trees, using hypergraph substitution instead of tree substitution. If every output hypergraph of the transducer is a jungle, i.e., a hypergraph that can be unfolded into a tree, then the treetograph transducer is said to be treegenerating and naturally defines a treetotree translation. We prove that bottomup treetograph transducers define the same treetotree translations as the previously introduced topdown treetograph transducers. This is in contrast with the wellknown incomparability of the usual bottomup and topdown tree transducers.