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- Wouter Gelade, Wim Martens, Frank Neven
- SIAM J. Comput.
- 2007

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)

- Geert Jan Bex, Wouter Gelade, Wim Martens, Frank Neven
- SIGMOD Conference
- 2009

Whether beloved or despised, XML Schema is momentarily the only industrially accepted schema language for XML and is unlikely to become obsolete any time soon. Nevertheless, many nontransparent restrictions unnecessarily complicate the design of XSDs. For instance, complex content models in XML Schema are constrained by the infamous unique particle… (More)

Inferring an appropriate DTD or XML Schema Definition (XSD) for a given collection of XML documents essentially reduces to learning <i>deterministic</i> regular expressions from sets of positive example words. Unfortunately, there is no algorithm capable of learning the complete class of deterministic regular expressions from positive examples only, as we… (More)

- Wouter Gelade, Frank Neven
- ACM Trans. Comput. Log.
- 2008

We study the succinctness of the complement and intersection of regular expressions. In particular, we show that when constructing a regular expression defining the complement of a given regular expression, a double exponential size increase cannot be avoided. Similarly, when constructing a regular expression defining the intersection of a fixed and an… (More)

- Wouter Gelade, Marc Gyssens, Wim Martens
- SIAM J. Comput.
- 2009

We study deterministic regular expressions extended with the counting operator. There exist two notions of determinism, strong and weak determinism, which almost coincide for standard regular expressions. This, however, changes dramatically in the presence of counting. In particular, we show that weakly deterministic expressions with counting are… (More)

- Wouter Gelade
- Theor. Comput. Sci.
- 2008

Studying the impact of operations, such as intersection and interleaving, on the succinctness of regular expressions has recently received renewed attention [12–14]. In this paper, we study the succinctness of regular expressions (REs) extended with interleaving, intersection and counting operators. We show that in a translation from REs with interleaving… (More)

- Henrik Björklund, Wouter Gelade, Wim Martens
- ACM Trans. Database Syst.
- 2009

Incremental view maintenance for XPath queries asks to maintain a materialized XPath view over an XML database. It assumes an underlying XML database <i>D</i> and a query <i>Q</i>. One is given a sequence of updates <i>U</i> to <i>D</i>, and the problem is to compute the result of <i>Q</i>(<i>U</i>(<i>D</i>)): the result of evaluating query <i>Q</i> on… (More)

- Wenfei Fan, Floris Geerts, Wouter Gelade, Frank Neven, Antonella Poggi
- PODS
- 2008

The paper investigates fundamental decision problems and composition synthesis for Web services commonly found in practice. We propose a notion of <i>synthesized Web services</i> (ASTs) to specify the behaviors of the services. Upon receiving a sequence of input messages, an AST issues multiple queries to a database and generates actions, in parallel; it… (More)

- Wouter Gelade, Marcel Marquardt, Thomas Schwentick
- STACS
- 2009

The article investigates the power of the dynamic complexity classes D<scp>yn</scp>FO, D<scp>yn</scp>QF, and D<scp>yn</scp>PROP over string languages. The latter two classes contain problems that can be maintained using quantifier-free first-order updates, with and without auxiliary functions, respectively. It is shown that the languages maintainable in… (More)

- Wouter Gelade, Tomasz Idziaszek, Wim Martens, Frank Neven
- PODS
- 2010

XML Schema Definitions (XSDs) can be adequately abstracted by the single-type regular tree languages. It is well-known, that these form a strict subclass of the robust class of regular unranked tree languages. Sadly, in this respect, XSDs are not closed under the basic operations of union and set difference, complicating important tasks in schema… (More)