@misc{Meliou-diploma,
    Abstract = {The XML Language is becoming the new standard for storing and
    exchanging knowledge through the internet. XML data incorporate structure
    and data in one entity. The data model of XML is a graph representation of
    a collection of atomic and complex objects. Under certain conditions, the
    XML data model becomes a schema tree. Schema trees are rooted ordered
    labeled trees that express the structural relationships between the nodes
    of an XML document. Schema trees are used to represent not only XML
    documents, but also complex data. The main purpose of this thesis is to
    explore the algebraic properties of hierarchical structures. Given two or
    more trees we define new trees by applying operators like union,
    intersection, difference. These operators are defined in such a way that
    they obey laws similar to the ones of set theory. We study the conditions
    under which these operators are applicable, and we present algorithms to
    implement the operators and check their validity.},
    Author = {Meliou, Alexandra},
    Howpublished = {Diploma thesis, National Technical University of Athens},
    Title = {\href{http://www.dblab.ece.ntua.gr/pubs/uploads/DIPL-2003-07.pdf}{Modeling and Exploring the Algebraic Properties of Hierarchical Structures}},
    Venue = {BSc},
    address = {Athens, Greece},
    month = may,
    Year = {2003}
}