Aiming at ontology-based data access to temporal data, we design two-dimensional temporal ontology and query languages by combining logics from the (extended) DL-Lite family with linear temporal logic LTL over discrete time (Z,<). Our main concern is first-order rewritability of ontology-mediated queries (OMQs) that consist of a 2D ontology and a positive temporal instance query. Our target languages for FO-rewritings are two-sorted FO(<) - first-order logic with sorts for time instants ordered by the built-in precedence relation < and for the domain of individuals - its extension FOE with the standard congruence predicates t \equiv 0 mod n, for any fixed n > 1, and FO(RPR) that admits relational primitive recursion. In terms of circuit complexity, FOE- and FO(RPR)-rewritability guarantee answering OMQs in uniform AC0 and NC1, respectively. We proceed in three steps. First, we define a hierarchy of 2D DL-Lite/LTL ontology languages and investigate the FO-rewritability of OMQs with atomic queries by constructing projections onto 1D LTL OMQs and employing recent results on the FO-rewritability of propositional LTL OMQs. As the projections involve deciding consistency of ontologies and data, we also consider the consistency problem for our languages. While the undecidability of consistency for 2D ontology languages with expressive Boolean role inclusions might be expected, we also show that, rather surprisingly, the restriction to Krom and Horn role inclusions leads to decidability (and ExpSpace-completeness), even if one admits full Booleans on concepts. As a final step, we lift some of the rewritability results for atomic OMQs to OMQs with expressive positive temporal instance queries. The lifting results are based on an in-depth study of the canonical models and only concern Horn ontologies.
翻译:以基于科学的数据为目的获取时间数据,我们设计了二维时间信息学和查询语言,将(扩展的)DL-Lite家族的逻辑与离散时间(Z, <)的线性时间逻辑LTLL(T)相结合。我们的主要关切是,由2D肿瘤和积极的时间实例查询组成的本科学中介查询(OMQs)的一阶重写性。我们FO-refrict的目标语言是双分解 FO( < ) - 一阶逻辑,由(扩展的)DL-Lite家族的立体关系和(个人域)的直线性-直线性直线性逻辑结合逻辑(LT)的逻辑和线性时间逻辑(LL)的逻辑。从电路的复杂性、FOE-和FO(RPR)的易变异性(FO-LLT)的立体(OFOR-LLT)的直线性、OFO-LLLL的直径预测(OLL)的直径直径直径直径直径直径直径直径直径直径直径(O-LL)的直径、O-LLLLL)的直径直径直径直径直径直径直判的直判(O-LLL)的直判的直径直径直判)的直判(O)的直径直径直径直径直判)的直判(O)的直判)的直判)的直判(O。