The paper analyzes and characterizes the algebraic and logical structure of the multiset semantics for SPARQL patterns involving AND, UNION, FILTER, EXCEPT, and SELECT. To do this, we align SPARQL with two well-established query languages: Datalog and Relational Algebra. Specifically, we study (i) a version of non-recursive Datalog with safe negation extended to support multisets, and (ii) a multiset relational algebra comprising projection, selection, natural join, arithmetic union, and except. We prove that these three formalisms are expressively equivalent under multiset semantics.

翻译：本文分析并刻画了涉及AND、UNION、FILTER、EXCEPT和SELECT的SPARQL模式在多重集语义下的代数与逻辑结构。为此，我们将SPARQL与两种成熟的查询语言——Datalog和关系代数——进行对齐。具体而言，我们研究了（i）一种扩展了安全否定并支持多重集的非递归Datalog版本，以及（ii）一种包含投影、选择、自然连接、算术并集和差集运算的多重集关系代数。我们证明这三种形式化系统在多重集语义下具有表达等价性。