Automata Approach to XML Data Indexing: Selecting Unknown Nodes

Tato práce je součástí projektu "Indexování XML dokumentů pomocí automatů". Popisuje existující metody pro indexování XML dokumentů, které jsou založeny na teorii automatů, a jejich rozšíření, za účelem umožnění efektivního zpracování XPath dotazů skládajících se z libovolné kombinace child (/), descendant-or-self (//) os a asterisk (*) a nodename node testů, sloužících k navigaci v XML dokumentu. Ke konstrukci indexu pro daný XML dokument D s n elementy je využít odpovídající XML stromový model T. Zpracování dotazu Q o velikosti m proběhne v čase O(m) nezávislém na n. Tato práce obsahuje též diskuzi ohledně časové a paměťové složitosti pro každou z navržených metod. Všechny nově popsané algoritmy jsou implementovány a otestovány na reálních datech.Being a part of the "Automata Approach to XML Data Indexing" project, this thesis is concerned with studying the existing methods of indexes creation algorithms based on the automata theory and extending them to deal with more significant fragment of XPath queries. The presented methods allow us to construct XML data indexes that support evaluation of all XPath queries using any combinations of child (/), descendant-or-self (//) axes, asterisk (*) and nodename node tests. Given an XML document D and its corresponding XML tree model T with n nodes, the tree is preprocessed and the index for the document D is constructed. The searching phase time of each of the constructed indexes for a query Q is bounded by O(m), where m is size of the query Q, and does not depend on the indexed XML document size n. Moreover, the space and time complexities for each of the proposed indexes are discussed, all the introduced algorithms are implemented and tested over the real-life datasets

Automata Approach to XML Data Indexing: Implementation and Experimental Evaluation

Tato práce se zabývá implementací a experimentálním vyhodnocením metod pro indexování XML dokumentů. Konkrétně se jedná o metody Tree String Path Automaton (TSPA), Tree String Path Subsequence Automaton (TSPSA) a Tree Path Automaton (TPA). Tyto metody jsou založeny na teorii konečných automatů a umožňují nalezení odpovědi pro omezenou podmnožinu XPath dotazů (obsahující pouze ${/,//}$ přechody a jejich kombinaci) v lineárním čase délky dotazu. Jednotlivé metody jsou v této práci implementovány jako Java knihovna. K předzpracování XML dokumentu je použita knihovna SAX. Hlavní část práce se venuje popisu, implementaci a podmínkám behu experimentu. V práci jsou prezentovány provedené experimenty. Tyto experimenty zkoumají, jak závisí vlastnosti indexu na velikosti (hloubce, šírce) vstupního XML souboru. Při tvorbě indexu měříme spotřebu RAM a čas. Proto XML dokumenty použity pro experimenty tvoří set s navzájem různými klíčovými parametry (např. průměrná hloubka, maximální hloubka, velikost, počet listů). V závěru práce jsou graficky prezentovány výsledky experimentů. Ve výsledné knihovně je zabudována podpora pro spuštění výše zmíněného experimentálního prostředí.This thesis deals with implementation and an experimental evaluation of some XML data indexing methods. The methods are as follows:Tree String Path Automaton (TSPA), Tree String Path Subsequence Automaton (TSPSA) and Tree Path Automaton (TPA). All of these methods are based on the theory of finite automata and answer a limited subset of XPath query (limited to ${/,//}$ transitions and their combination) in linear time to the length of the query. They are implemented as a Java library. SAX library is used to preprocess an XML document. The main part of the thesis is dedicated to a description, an implementation and conditions under which experiments are conducted. In the thesis experiments are run to clarify relations between Size/Depth/Width of an XML document and RAM consumption/Time to build an index. The chosen XML documents, which are presented in this thesis, form a set of mutually different documents in crucial aspects (average depth, maximal depth, size, number of leaves). Results of the conducted experiments are described in the end of the thesis. There is built-in support for experimental environment in the resulting Java library

Automata Approach to XML Data Indexing

The internal structure of XML documents can be viewed as a tree. Trees are among the fundamental and well-studied data structures in computer science. They express a hierarchical structure and are widely used in many applications. This paper focuses on the problem of processing tree data structures; particularly, it studies the XML index problem. Although there exist many state-of-the-art methods, the XML index problem still belongs to the active research areas. However, existing methods usually lack clear references to a systematic approach to the standard theory of formal languages and automata. Therefore, we present some new methods solving the XML index problem using the automata theory. These methods are simple and allow one to efficiently process a small subset of XPath. Thus, having an XML data structure, our methods can be used efficiently as auxiliary data structures that enable answering a particular set of queries, e.g., XPath queries using any combination of the child and descendant-or-self axes. Given an XML tree model with n nodes, the searching phase uses the index, reads an input query of size m, finds the answer in time O ( m ) and does not depend on the size of the original XML document

Automata Approach to XML Data Indexing

The internal structure of XML documents can be viewed as a tree. Trees are among the fundamental and well-studied data structures in computer science. They express a hierarchical structure and are widely used in many applications. This paper focuses on the problem of processing tree data structures; particularly, it studies the XML index problem. Although there exist many state-of-the-art methods, the XML index problem still belongs to the active research areas. However, existing methods usually lack clear references to a systematic approach to the standard theory of formal languages and automata. Therefore, we present some new methods solving the XML index problem using the automata theory. These methods are simple and allow one to efficiently process a small subset of XPath. Thus, having an XML data structure, our methods can be used efficiently as auxiliary data structures that enable answering a particular set of queries, e.g., XPath queries using any combination of the child and descendant-or-self axes. Given an XML tree model with n nodes, the searching phase uses the index, reads an input query of size m, finds the answer in time O ( m ) and does not depend on the size of the original XML document