Learning tree patterns for syntactic parsing

This paper presents a method for parsing Hungarian texts using a machine learning approach. The method collects the initial grammar for a learner from an annotated corpus with the help of tree shapes. The PGS algorithm, an improved version of the RGLearn algorithm, was developed and applied to learning tree patterns with various phrase types described by regular expressions. The method also calculates the probability values of the learned tree patterns. The syntactic parser of learned grammar using the Viterbi algorithm performs a quick search for finding the most probable derivation of a sentence. The results were built into an information extraction pipeline

Parsing and reflective printing, bidirectionally

Language designers usually need to implement parsers and printers. Despite being two intimately related programs, in practice they are often designed separately, and then need to be revised and kept consistent as the language evolves. It will be more convenient if the parser and printer can be unified and developed in one single program, with their consistency guaranteed automatically.Furthermore, in certain scenarios (like showing compiler optimisation results to the programmer), it is desirable to have a more powerful reflective printer that, when an abstract syntax tree corresponding to a piece of program text is modified, can reflect the modification to the program text while preserving layouts, comments, and syntactic sugar.To address these needs, we propose a domain-specific language BIYACC, whose programs denote both a parser and a reflective printer for an unambiguous context-free grammar. BIYACC is based on the theory of bidirectional transformations, which helps to guarantee by construction that the pairs of parsers and reflective printers generated by BIYACC are consistent. We show that BIYACC is capable of facilitating many tasks such as Pombrio and Krishnamurthi's "resugaring", simple refactoring, and language evolution.We would like to thank reviewers for their valuable comments. This work was partially supported by the Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for Scientific Research (A) No. 25240009

Unifying parsing and reflective printing for fully disambiguated grammars

Language designers usually need to implement parsers and printers. Despite being two closely related programs, in practice they are often designed separately, and then need to be revised and kept consistent as the language evolves. It will be more convenient if the parser and printer can be unified and developed in a single program, with their consistency guaranteed automatically. Furthermore, in certain scenarios (like showing compiler optimisation results to the programmer), it is desirable to have a more powerful reflective printer that, when an abstract syntax tree corresponding to a piece of program text is modified, can propagate the modification to the program text while preserving layouts, comments, and syntactic sugar. To address these needs, we propose a domain-specific language BiYacc, whose programs denote both a parser and a reflective printer for a fully disambiguated context-free grammar. BiYacc is based on the theory of bidirectional transformations, which helps to guarantee by construction that the generated pairs of parsers and reflective printers are consistent. Handling grammatical ambiguity is particularly challenging: we propose an approach based on generalised parsing and disambiguation filters, which produce all the parse results and (try to) select the only correct one in the parsing direction; the filters are carefully bidirectionalised so that they also work in the printing direction and do not break the consistency between the parsers and reflective printers. We show that BiYacc is capable of facilitating many tasks such as Pombrio and Krishnamurthi's 'resugaring', simple refactoring, and language evolution.We thank the reviewers and the editor for their selflessness and effort spent on reviewing our paper, a quite long one. With their help, the readability of the paper is much improved, especially regarding how several case studies are structured, how theorems for the basic BiYacc and theorems for the extended version handling ambiguous grammars are related, and how look-alike notions are `disambiguated'. This work is partially supported by the Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for Scientific Research (S) No. 17H06099; in particular, most of the second author's contributions were made when he worked at the National Institute of Informatics and funded by the Grant

A survey of compiler development aids

A theoretical background was established for the compilation process by dividing it into five phases and explaining the concepts and algorithms that underpin each. The five selected phases were lexical analysis, syntax analysis, semantic analysis, optimization, and code generation. Graph theoretical optimization techniques were presented, and approaches to code generation were described for both one-pass and multipass compilation environments. Following the initial tutorial sections, more than 20 tools that were developed to aid in the process of writing compilers were surveyed. Eight of the more recent compiler development aids were selected for special attention - SIMCMP/STAGE2, LANG-PAK, COGENT, XPL, AED, CWIC, LIS, and JOCIT. The impact of compiler development aids were assessed some of their shortcomings and some of the areas of research currently in progress were inspected

Nachweis des entfernten Nachbargruppeneffekts in Glykosylierungen durch kalte Infrarotspektroskopie

Controlling the stereochemistry during glycosynthesis is usually achieved by using elaborate protecting group techniques. For example, 1,2-trans-glycosidic bonds are formed by the introduction of participating protecting groups at the neighboring C2-position. This reaction is believed to proceed via a glycosyl cation, where the protecting group interacts with the positive charge at the anomeric carbon, effectively shielding the cis-side from nucleophilic attack, leading to the concept of neighboring group participation. The formation of 1,2-cis-glycosidic bonds remains, however, a major hurdle to date. Empirical studies have shown that their formation can be aided by the introduction of participating protecting groups at the remote C4- or C6-positions, leading to the phenomenon of remote participation. Due to the short-lived nature of glycosyl cations, they cannot be studied readily in the condensed phase. The gas-phase environment inside a mass spectrometer, however, can be used to isolate them. In a recent publication, cryogenic infrared spectroscopy was used to unravel the structure of glycosyl cations. Evidence for the existence of neighboring group participation was found in various monosaccharide building blocks, as the acetyl protecting group at the C2-position forms a covalent bond with the anomeric carbon. While these results enable a better understanding of neighboring group participation, the structural motifs underlying remote participation remain poorly understood. Their study would help optimizing reaction conditions aiding the formation of 1,2-cis-glycosidic bonds. Here, a combination of first-principles theory and cryogenic infrared spectroscopy in the low-temperature environment of superfluid helium droplets (0.4 K) is used to decipher the structure of galactose building blocks exhibiting remote participation. Galactose building blocks carrying an acetyl protecting group at the C4-position form α-selective dioxolenium-type structures, exhibiting a covalent bond between the anomeric carbon and the oxygen atom of the carbonyl group of the acetyl protecting group. Contrary, galactose carrying an acetyl group solely at the C6-position does not exhibit remote participation and forms non-selective oxocarbenium-type structures. Furthermore, a novel type of interaction between benzyl protecting groups and the anomeric carbon, leading to α-selective oxonium-type structures, is observed. The recorded data can be used by algorithms based on artificial intelligence to predict the best reaction conditions for performing glycosylation reactions with a defined stereochemical outcome

A programming language and compiler based on an augmentation of the ACM model

Call number: LD2668 .T4 CMSC 1987 S54Master of ScienceComputing and Information Science

Distributed management: implementation issues

Management processes have to react on time to the new challenges put by a crescent movement of the computing world to the Internet paradigm. The enormous base of legacy knowledge and legacy systems leads the SNMP management framework to a necessary choice in nowadays management scenarios. However, even with the recent SNMPv3, its services correspond roughly to low-level operations for setting or retrieving network equipment parameters. The IETF Distributed Management working group have been producing normalization documents that intent to apply to the enrichment of SNMP semantics, especially in what concerns the processing of management information. This paper will present the recent outcome of this WG and will discuss an implementation project that aims to apply mobile agent technology in these scenarios