Theoretical Computer Science
Finding Regular Simple Paths in Graph Databases
SIAM Journal on Computing
A lower bound technique for the size of nondeterministic finite automata
Information Processing Letters
Intractability of decision problems for finite-memory automata
Theoretical Computer Science - Special issue on universal machines and computations
Introduction to the Theory of Computation
Introduction to the Theory of Computation
Automata theory for XML researchers
ACM SIGMOD Record
Finite state machines for strings over infinite alphabets
ACM Transactions on Computational Logic (TOCL)
ACM Transactions on Database Systems (TODS) - Special Issue: SIGMOD/PODS 2004
Journal of Computer and System Sciences
Regular Expressions for Languages over Infinite Alphabets
Fundamenta Informaticae
Survey of graph database models
ACM Computing Surveys (CSUR)
XPath evaluation in linear time
Proceedings of the twenty-seventh ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
LTL with the freeze quantifier and register automata
ACM Transactions on Computational Logic (TOCL)
Satisfiability of downward XPath with data equality tests
Proceedings of the twenty-eighth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Graph Reachability and Pebble Automata over Infinite Alphabets
LICS '09 Proceedings of the 2009 24th Annual IEEE Symposium on Logic In Computer Science
Expressive languages for path queries over graph-structured data
Proceedings of the twenty-ninth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Automata vs. logics on data words
CSL'10/EACSL'10 Proceedings of the 24th international conference/19th annual conference on Computer science logic
An Extension of Data Automata that Captures XPath
LICS '10 Proceedings of the 2010 25th Annual IEEE Symposium on Logic in Computer Science
Two-variable logic on data words
ACM Transactions on Computational Logic (TOCL)
On the use of guards for logics with data
MFCS'11 Proceedings of the 36th international conference on Mathematical foundations of computer science
Automata and logics for words and trees over an infinite alphabet
CSL'06 Proceedings of the 20th international conference on Computer Science Logic
Variable automata over infinite alphabets
LATA'10 Proceedings of the 4th international conference on Language and Automata Theory and Applications
Regular path queries on graphs with data
Proceedings of the 15th International Conference on Database Theory
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In data words, each position carries not only a letter form a finite alphabet, as the usual words do, but also a data value coming from an infinite domain. There has been a renewed interest in them due to applications in querying and reasoning about data models with complex structural properties, notably XML, and more recently, graph databases. Logical formalisms designed for querying such data often require concise and easily understandable presentations of regular languages over data words. Our goal, therefore, is to define and study regular expressions for data words. As the automaton model, we take register automata, which are a natural analog of NFAs for data words. We first equip standard regular expressions with limited memory, and show that they capture the class of data words defined by register automata. The complexity of the main decision problems for these expressions (nonemptiness, membership) also turns out to be the same as for register automata. We then look at a subclass of these regular expressions that can define many properties of interest in applications of data words, and show that the main decision problems can be solved efficiently for it.