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，程序性任务仍能以基于逻辑的声明式方式建模。本文聚焦于有限访问模式下的查询处理任务——这是数据库文献中一个经典问题。我们证明LIF非常适合建模该任务。为此，我们在一阶设置中引入LIF的一个变体，称为"前向"LIF（FLIF）。FLIF采用新颖的图导航方法，是一种类似XPath的语言，但被证明等价于Nash和Ludäscher定义的"可执行"一阶逻辑片段。FLIF表达式中的变量还可分类为输入和输出。当输入和输出不相交时（称为io-不相交FLIF表达式），这些表达式能特别清晰地翻译成遵守访问限制的代数查询计划。最后，我们证明通用FLIF表达式总可转换为io-不相交形式。