A compatibility relation on letters induces a reflexive and symmetric relation on words of equal length. We consider these word relations with respect to the theory of variable length codes and free monoids. We define an -code and an -free monoid for arbitrary word relations and . Modified Sardinas-Patterson algorithm is presented for testing whether finite sets of words are -codes. Coding capabilities of relational codes are measured algorithmically by finding minimal and maximal relations. We generalize the stability criterion of Schützenberger and Tilson’s closure result for -free monoids. The -free hull of a set of words is introduced and we show how it can be computed. We prove a defect theorem for -free hulls. In addition, a defect theorem of partial words is proved as a corollary.
@article{ITA_2008__42_3_539_0, author = {K\"arki, Tomi}, title = {Compatibility relations on codes and free monoids}, journal = {RAIRO - Theoretical Informatics and Applications - Informatique Th\'eorique et Applications}, volume = {42}, year = {2008}, pages = {539-552}, doi = {10.1051/ita:2008016}, mrnumber = {2434034}, zbl = {1149.68069}, language = {en}, url = {http://dml.mathdoc.fr/item/ITA_2008__42_3_539_0} }
Kärki, Tomi. Compatibility relations on codes and free monoids. RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications, Tome 42 (2008) pp. 539-552. doi : 10.1051/ita:2008016. http://gdmltest.u-ga.fr/item/ITA_2008__42_3_539_0/
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