The logic of information flows (LIF) has recently been proposed as a general framework in the field of knowledge representation. In this framework, tasks of procedural nature can still be modeled in a declarative, logic-based fashion. In this paper, we focus on the task of query processing under limited access patterns, a well-studied problem in the database literature. We show that LIF is well-suited for modeling this task. Toward this goal, we introduce a variant of LIF called "forward" LIF (FLIF), in a first-order setting. FLIF takes a novel graph-navigational approach; it is an XPath-like language that nevertheless turns out to be equivalent to the "executable" fragment of first-order logic defined by Nash and Lud\"ascher. One can also classify the variables in FLIF expressions as inputs and outputs. Expressions where inputs and outputs are disjoint, referred to as io-disjoint FLIF expressions, allow a particularly transparent translation into algebraic query plans that respect the access limitations. Finally, we show that general FLIF expressions can always be put into io-disjoint form.

翻译：信息流逻辑（LIF）最近被提出作为知识表示领域的一个通用框架。在该框架中，过程性任务仍能以声明式、基于逻辑的方式建模。本文聚焦于受限访问模式下的查询处理任务——这是数据库文献中一个研究充分的问题。我们证明LIF非常适合对该任务进行建模。为此，我们在一阶逻辑设定下引入LIF的变体——"前向"信息流逻辑（FLIF）。FLIF采用新颖的图导航方法，是一种类似XPath的语言，但事实证明其等价于Nash和Ludäscher定义的一阶逻辑"可执行"片段。FLIF表达式中的变量还可被分类为输入和输出。输入与输出不相交的表达式（称为io-不相交FLIF表达式）能够特别清晰地翻译为遵守访问限制的代数查询计划。最后，我们证明一般FLIF表达式总可转化为io-不相交形式。