On Structures of Sign‐Boundary and Diagonal Vacancy‐Type Standard Contradictions

ABSTRACT Automated deduction based on contradiction separation extends the binary resolution principle, offering a novel approach to deductive inference rules. Constructing standard contradictions is essential for its efficiency. This paper systematically investigates two new types of standard contradictions in propositional and first‐order logic, enriching the library of standard contradictions and enhancing its effectiveness. First, we define two types of standard contradictions: sign‐boundary contradictions and diagonal vacancy‐type contradictions. Next, we propose the corresponding construction methods and present their properties related to contradiction composition and literal addition. Furthermore, we explore the transformations between these two types of contradictions and analyze the conditions necessary to construct standard contradictions. Finally, we extend these findings to first‐order logic, demonstrating their applicability in more complex logical systems.