Papers by Reza Kurniawan chandra
XPath is a simple language for navigating an XML tree and returning a set of answer nodes. The fo... more XPath is a simple language for navigating an XML tree and returning a set of answer nodes. The focus in this paper is on the complexity of the containment problem for various fragments of XPath. In addition to the basic operations (child, descendant, filter, and wildcard), we consider disjunction, DTDs and variables. W.r.t. variables we study two semantics: (1) the value of variables is given by an outer context; (2) the value of variables is defined existentially. We establish an almost complete classification of the complexity of the containment problem w.r.t. these fragments. Definition 2. A DTD is a tuple (d, S d , Σ d) where Σ d is a finite subset of Σ, S d ∈ Σ d is the start symbol, and d is a mapping from Σ d to the set of regular expressions over Σ d. A tree t matches a DTD d iff lab t (ε) = S d and for every u ∈ dom(t) with n children, lab t (u1) • • • lab t (un) ∈ L(d(lab(u))). We denote by L(d) the set of all trees that satisfy d. Note that DTDs do not constrain the value of attributes in any way. We usually refer to a DTD by d rather than (d, S d , Σ d). We next define the core fragment of XPath that we will consider in Sections 3 and 4.
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Papers by Reza Kurniawan chandra