Abstract: Methods for efficiently obtaining answers to queries in a database (DB) environment include forming tree automata (TA), processing semi-structured data using the TA to provide indexed data, pruning the indexed data to obtain pruned data and performing a join operation to join either the pruned data or the semi-structured data to provide the answers. The queries relate to data stored as semi-structured data. In some embodiments, the TA is unordered.

Abstract: To answer one or more queries of semistructured data, an answer automaton is constructed, based at least in part on the queries and on a schema of the data. The answer automaton is applied to the data to answer the queries. Preferably, to construct the answer automaton, a schema automaton is constructed for the schema, a query automaton is constructed for the queries, and the schema automaton and the query automaton are merged. If there are more than one query, separate query automata are constructed for the different queries and then are united to provide a joint query automaton. Preferably, all the automata are deterministic finite automata. Most preferably, all the automata are isostate automata.

Abstract: A method of generating a parser of a source code file that references a syntactic dictionary, a method of compressing the file, and apparatuses that use the methods. The syntactic dictionary is converted into a corresponding plurality of expressions, of a context-free grammar, that are a grammar of the source code. The parser is constructed from the expressions. The source code is compressed using the parser. Preferably, the grammar of the source code file is a D-grammar and the expressions are regular expressions. Preferably, the parser is a deterministic pushdown transducer. An important case of the present invention is that in which the source code is XML code and the syntactic dictionary is the document type declaration of the XML code. Apparatuses that use a parser of the present invention include compressors, decompressors, validators, converters, editors, network devices and end-user/hand-held devices.