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Motivated by formal models recently proposed in the context of XML, we study automata and logics on strings over infinite alphabets. These are conservative extensions of classical automata and logics defining the regular languages on finite alphabets. Specifically, we consider register and pebble automata, and extensions of first-order logic and monadic(More)
The common abstraction of XML Schema by unranked regular tree languages is not entirely accurate. To shed some light on the actual expressive power of XML Schema, intuitive semantical characterizations of the Element Declarations Consistent (EDC) rule are provided. In particular, it is obtained that schemas satisfying EDC can only reason about regular(More)
Motivated by a recent conjecture concerning the expressiveness of declarative networking, we propose a formal computation model for "eventually consistent" distributed querying, based on relational transducers. A tight link has been conjectured between coordination-freeness of computations, and monotonicity of the queries expressed by such computations.(More)
The advent of XML initiated a symbiosis between document research, databases and formal languages (see, e.g., the survey by Vianu [38]). This symbio-sis resulted, for instance, in the development of un-ranked tree automata [3]. In brief, unranked trees are finite labeled trees where nodes can have an ar-bitraxy number of children. So, there is no fixed rank(More)
We survey some recent developments in the broad area of automata and logic which are motivated by the advent of XML. In particular , we consider unranked tree automata, tree-walking automata, and automata over infinite alphabets. We focus on their connection with logic and on questions imposed by XML.
We consider the problem to infer a concise Document Type Definition (DTD) for a given set of XML-documents, a problem which basically reduces to learning of concise regular expressions from positive example strings. We identify two such classes: single occurrence regular expressions (SOREs) and chain regular expressions (CHAREs). Both classes capture the(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. We restrict attention to the most common XPath expressions which navigate along the child and/or descendant axis. In addition to basic expressions using only node(More)
Motivated by the need to export relational databases as XML data in the context of the Web, we investigate the <i>typechecking</i> problem for transformations of relational data into tree data (XML). The problem consists of statically verifying that the output of every transformation belongs to a given output tree language (specified for XML by a DTD), for(More)
The presence of a schema offers many advantages in processing, translating, querying, and storage of XML data. Basic decision problems like equivalence, inclusion, and non-emptiness of intersection of schemas form the basic building blocks for schema optimization and integration, and algorithms for static analysis of transformations. It is thereby paramount(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:(More)