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arXiv · 1906.06070

Complexity of Dependencies in Bounded Domains, Armstrong Codes, and Generalizations

Yeow Meng Chee·Hui Zhang·Xiande Zhang
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Abstract

The study of Armstrong codes is motivated by the problem of understanding complexities of dependencies in relational database systems, where attributes have bounded domains. A $(q,k,n)$-Armstrong code is a $q$-ary code of length $n$ with minimum Hamming distance $n-k+1$, and for any set of $k-1$ coordinates there exist two codewords that agree exactly there. Let $f(q,k)$ be the maximum $n$ for which such a code exists. In this paper, $f(q,3)=3q-1$ is determined for all $q\geq 5$ with three possible exceptions. This disproves a conjecture of Sali. Further, we introduce generalized Armstrong codes for branching, or $(s,t)$-dependencies, construct several classes of optimal Armstrong codes and establish lower bounds for the maximum length $n$ in this more general setting.

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BibTeXRIS

Yeow Meng Chee, Hui Zhang, Xiande Zhang. 2019-06-14. Complexity of Dependencies in Bounded Domains, Armstrong Codes, and Generalizations. https://arxiv.org/abs/1906.06070

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