Regular Expression Containment with xs:all-like Operators

We discuss containment checking for regular expressions with operators like XML Schema's xs:all, that is, the operator that allows a sequence of letters to occur in arbitrary order. In this report, we model this operator by &, and give several algorithms of containment checking for regular expressions with &. Our algorithms are based on the notion of the permutability of word languages

Formalization and Analysis of Class Loading in Java

Since the Java security relies on the type-safety of the JVM, many formal approaches have been taken in order to prove the soundness of the JVM. This paper presents a new formalization of the JVM, which is enough to analyze the loading constraint scheme of Java2. The key notion required for proving the soundness of the new model is the augmented value typing, which is defined from the ordinary value typing combined with the loading constraint scheme. During proving the soundness of the model using the notion, we found three problems inside the current ocial implementation of the JVM with respect to our model. We also analyzed the newly introduced findClass scheme, and as a result, we can answer the old question why applets cannot cause Saraswat's problem. A new method to implement the loading constraint scheme efficiently is another outcome of the analysis

XML Validation for Context-Free Grammars

Abstract. String expression analysis conservatively approximates the possible string values generated by a program. We consider the validation of a context-free grammar obtained by the analysis against XML schemas and develop two algorithms for deciding inclusion L(G1) ⊆ L(G2) where G1 is a context-free grammar and G2 is either an XML-grammar or a regular hedge grammar. The algorithms for XML-grammars and regular hedge grammars have exponential and doubly exponential time complexity, respectively. We have incorporated the algorithms into the PHP string analyzer and validated several publicly available PHP programs against the XHTML DTD. The experiments show that both of the algorithms are efficient in practice although they have exponential complexity.

Complexity Results on Balanced Context-Free Languages

Abstract. Some decision problems related to balanced context-free languages are important for their application to the static analysis of programs generating XML strings. One such problem is the balancedness problem which decides whether or not the language of a given contextfree grammar (CFG) over a paired alphabet is balanced. Another important problem is the validation problem which decides whether or not the language of a CFG is contained by that of a regular hedge grammar (RHG). This paper gives two new results; (1) the balancedness problem is in PTIME; and (2) the CFG-RHG containment problem is 2EXPTIMEcomplete.

Efficient Decision Procedure for a Logic for XML

Abstract. In this paper, we investigate formal verification techniques to solve decision problems in the world of XML. Such problems can be uniformly modeled by formulas of a modal logic defined on XML trees and having general least and greatest fixpoint operators. This logic, called BTL, can be seen as a variation on alternating-free full µ-calculus. BTL sufficiently captures XPath, a path language for querying XML, and thus models type-checking problems for XPathbased XML transformation. We then give an efficient procedure that decides the satisfiability of a formula of this logic, which extends the procedure by Pan et al to handle both two-way modalities and fixpoints of BTL. Our experiment verifies its efficiency through real-world XPath containment and XSLT type-checking problems