On the Regularity and Learnability of Ordered DAG Languages

  • Henrik BjörklundEmail author
  • Johanna Björklund
  • Petter Ericson
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 10329)


Order-Preserving DAG Grammars (OPDGs) is a subclass of Hyper-Edge Replacement Grammars that can be parsed in polynomial time. Their associated class of languages is known as Ordered DAG Languages, and the graphs they generate are characterised by being acyclic, rooted, and having a natural order on their nodes. OPDGs are useful in natural-language processing to model abstract meaning representations. We state and prove a Myhill-Nerode theorem for ordered DAG languages, and translate it into a MAT-learning algorithm for the same class. The algorithm infers a minimal OPDG G for the target language in time polynomial in G and the samples provided by the MAT oracle.


Directed Acyclic Graph Tree Automaton Membership Problem External Node Membership Query 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



We thank the anonymous reviewers for their careful reading of our manuscript and their helpful comments.


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Copyright information

© Springer International Publishing AG 2017

Authors and Affiliations

  • Henrik Björklund
    • 1
    Email author
  • Johanna Björklund
    • 1
  • Petter Ericson
    • 1
  1. 1.Department of Computing ScienceUmeå UniversityUmeåSweden

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