基于Web的达梦数据库交互式查询工具的实现

本系统主要功能：对用户输入的单句或多句SQL语句进行处理,及时返回查询结果或者操作信息。本系统具有以下特点：采用主流的Web设计语言JSP设计客户端界面,用JDBC实现对数据库的无缝连接;使用JDBC扩展包中的行集来缓存结果集;使用javacc工具自动生成语法分析器;这些后台操作大部分采用了JavaBeans进行封装。     

Grammar semantics, analysis and parsing by abstract interpretation

We study abstract interpretations of a fixpoint protoderivation semantics defining the maximal derivations of a transitional semantics of context-free grammars akin to pushdown automata. The result is a hierarchy of bottom-up or top-down semantics refining the classical equational and derivational language semantics and including Knuth grammar problems, classical grammar flow analysis algorithms and parsing algorithms.     

合成目标化合物析分系统

在化学反应处理的计算模型的基础上,完成了一个实验性的目标化合物析分系统（Target Parsing System,TPS）。目前它主要用于测试和优化反应规则的选择和表述方法。TPS的工作逻辑基本上模仿人的思维过程,它通过对目标分子析分找出谋略键。根据谋略键将目标分子分拆成前体,再通过对原料库的检索确定是否已是可得原料等3个步骤完成反合成分析。通过对一些小分子和天然产物的测试,表明它已能给出令人满意的反合成分析结果。由于TPS在知识量上的局限性,对复杂化合物的析分还不可能达到实用水平。但是,可以预见通过对知识库的扩充和对TPS的不断完善,它有望发展成为一个真正意义上的计算机辅助合成设计系统。     

On the correct elimination of chain productions from lr parsers

A criterion is formally described which guarantees the correctness of a variety of chain-free LR parsers including the case of grammars containing ?-nonterminals. Using the criterion Pager's algorithm for the elimination of chain productions is shown to produce correct parsers for any compatible merging relation. Also, a mildly restricted version of a claim concerning chain-free SLR parsers made in [K&S 79] is proved correct.     

A simple system for generating efficient lexical scans

A language for specifying lexical scans is described.The language uses the model of a finite state automation with a limited back-up facility.It is efficiently implementable and is machine independent except for one statement which depends on the machine's character set.     

Producing the left parse during bottom-up parsing

Schmeiser and Barnard described a method for producing the left parse at the end of the bottom-up parsing process. We improve their method in the sense that the left parse is actually produced during the bottom-up parsing process (i.e., with considerably less delay).     

Preprocessing embedded actions

Some parser generators allow the user to attach actions, consisting of executable code, to syntax rules. Actions are usually in the local programming language, so they are simply copied into the generated parser. However, we show two situations in which it is convenient to allow actions to be in a different notation. A preprocessor is used to translate such notations into the local programming language. A preprocessor must know where to find actions and how to translate them. We show how these two activities can be programmed separately. Often, the user only has to worry about the second part: once the parser generator is known, the placement of the actions is known as well, so routines for finding actions can be separately compiled and linked in. Examples in the paper are based on the parser generator Yacc, but the approach is not limited to Yacc, or even to parser generators. Certain compositions of syntax-directed translations can be implemented by preprocessing actions.     

Even faster lr parsing

Conventional LR parser generators create tables which are used to drive a standard parser procedure. Much faster parsers can be obtained by compiling the table entries into code that is directly executed. A possible drawback with a directly executable parser is its large size. In this paper, we introduce optimization techniques that increase the parsing speed even further while simultaneously reducing the size of the parser.     

HUHU: The Hebrew University Hebrew Understander

This paper describes a system of morphological and syntactic parsing of the Hebrew language. It contains an extensive morphological analyzer and an augmented transition network-based syntactic parser. The system has been written in the YLISP dialect of Lisp. A parallel effort for English (different grammars that use the same parsing software) has also been developed.