Access Restriction

Author Colazzo, Dario ♦ Ghelli, Giorgio ♦ Sartiani, Carlo
Source CiteSeerX
Content type Text
File Format PDF
Language English
Subject Domain (in DDC) Computer science, information & general works ♦ Data processing & computer science
Subject Keyword Extended Re ♦ Ptime Inclusion Algorithm ♦ Important Use ♦ Human-defined Supertype ♦ Expressive Power ♦ Binary Intersection ♦ Asymmetric Inclusion ♦ Subtype Checking ♦ Subtype Position ♦ Candidate Subtype ♦ Excellent Complexity Behaviour ♦ Cubic Inclusion Algorithm ♦ Efficient Asymmetric Inclusion ♦ Linear Membership ♦ Regular Expression Type ♦ Xml Application ♦ Xml Manipulation Languges ♦ Symmetric Case ♦ Vast Majority ♦ Generalized Algorithm ♦ Conflict-free Limitation ♦ Type Checker Work ♦ Regular Expression ♦ Xml Schema Language ♦ Declared Supertypes ♦ Conflict-free Restriction ♦ Inferred Subtype ♦ Unrestricted Re ♦ Conflict-free Re ♦ Subtype Checking Algorithm ♦ Type-checking Algorithm ♦ Inferred Subtypes ♦ Content Model
Description In International Conference on Database Theory (ICDT
The inclusion of Regular Expressions (REs) is the kernel of any subtype checking algorithm for XML schema languages. XML applications would benefit from the extension of REs with interleaving and counting, but this is not feasible in general, since inclusion is EXPSPACE-complete for such extended REs. In [9] we introduced a notion of “conflict-free REs”, which are extended REs with excellent complexity behaviour, including a cubic inclusion algorithm [9] and linear membership [10]. Conflict-free REs have interleaving and counting, but the complexity is tamed by the “conflict-free” limitations, which have been found to be satisfied by the vast majority of the content models published on the Web. However, the most important use of subtype checking is in the context of type-cheching of XML manipulation languges. A type checker works by testing the inclusion of inferred subtypes in declared supertypes. The conflict-free restriction, while quite harmless for the human-defined supertype, is far too restrictive for the inferred subtype, whose shape is difficult to constrain. We show here that the PTIME inclusion algorithm can be actually extended to deal with totally unrestricted REs with counting and interleaving in the subtype position, provided that the supertype is conflict-free. This is exactly the expressive power that we need in order to use subtyping inside type-checking algorithms, and the cost of this generalized algorithm is only quadratic, which is as good as the best algorithm we have for the symmetric case (see [5]). The result is extremely surprising, since we had previously found that asymmetric inclusion becomes NP-hard as soon as the candidate subtype is enriched with binary intersection, a generalization that looked much more innocent than what we achieve here.
Educational Role Student ♦ Teacher
Age Range above 22 year
Educational Use Research
Education Level UG and PG ♦ Career/Technical Study
Learning Resource Type Article
Publisher Date 2009-01-01