On the relation between Context and Sequence Unification

Both Sequence and Context Unification generalize the same problem: Word Unification. Besides that, Sequence Unification solves equations between unranked terms involving sequence variables, and seems to be appealing for information extraction in XML documents, program transformation, knowledge representation, and rule-based programming. It is decidable. Context Unification deals with the same problem for ranked terms involving context variables, and has applications in computational linguistics and program transformation. Its decidability is a long-standing open question. In this work we study a relation between these two problems. We introduce a variant (restriction) of Context Unification, called Left-Hole Context Unification (LHCU), to which Sequence Unification is P-reduced: We define a partial currying procedure to translate sequence unification problems into left-hole context unification problems, and prove soundness of the translation. Furthermore, a precise characterization of...

• Type: Journal
• Year: 2010
• Where: JSC
• Authors: Temur Kutsia, Jordi Levy, Mateu Villaret
• Keywords: Context Unification, JSC 2010, Left-hole Context Unification, Sequence Unification