The recently introduced series of description logics under the common moniker
DL-Lite has attracted attention of the description logic and semantic web
communities due to the low computational complexity of inference, on the one
hand, and the ability to represent conceptual modeling formalisms, on the
other. The main aim of this article is to carry out a thorough and systematic
investigation of inference in extensions of the original DL-Lite logics along
five axes: by (i) adding the Boolean connectives and (ii) number restrictions
to concept constructs, (iii) allowing role hierarchies, (iv) allowing role
disjointness, symmetry, asymmetry, reflexivity, irreflexivity and transitivity
constraints, and (v) adopting or dropping the unique same assumption. We
analyze the combined complexity of satisfiability for the resulting logics, as
well as the data complexity of instance checking and answering positive
existential queries. Our approach is based on embedding DL-Lite logics in
suitable fragments of the one-variable first-order logic, which provides useful
insights into their properties and, in particular, computational behavior.

本文通过五个方面来深入系统地研究原始 DL-Lite 逻辑的扩展中的推理，分别是添加布尔连接符和数字限制到概念构造中，允许角色层次结构，允许角色的互斥、对称性、非对称性、自反性、反自反性和传递性约束，并接受或放弃同一性假设，同时分析了语言的可满足复杂性，验证数据复杂性和回答反面存在性查询的数据复杂性。

DL-Lite 家族与关系

The DL-Lite Family and Relations

So-called combined approaches answer a conjunctive query over a description
logic ontology in three steps: first, they materialise certain consequences of
the ontology and the data; second, they evaluate the query over the data; and
third, they filter the result of the second phase to eliminate unsound answers.
Such approaches were developed for various members of the DL-Lite and the EL
families of languages, but none of them can handle ontologies containing
nominals. In our work, we bridge this gap and present a combined query
answering approach for ELHO---a logic that contains all features of the OWL 2
EL standard apart from transitive roles and complex role inclusions. This
extension is nontrivial because nominals require equality reasoning, which
introduces complexity into the first and the third step. Our empirical
evaluation suggests that our technique is suitable for practical application,
and so it provides a practical basis for conjunctive query answering in a large
fragment of OWL 2 EL.

提出了一种用于 OWL 2 EL 子集内的联合查询应答的方法，该方法是基于一种称为 combined approaches 的方法实现的，该方法包括材料化本体和数据的某些后果、在数据上评估查询以及过滤第二阶段的结果以消除不合理的答案。该方法有助于在 OWL 2 EL 大片段中进行联合查询应答。

将名词引入联合查询方法以解决 EL 问题

Introducing Nominals to the Combined Query Answering Approaches for EL

We consider the setting of ontological database access, where an Abox is
given in form of a relational database D and where a Boolean conjunctive query
q has to be evaluated against D modulo a Tbox T formulated in DL-Lite or Linear
Datalog+/-. It is well-known that (T,q) can be rewritten into an equivalent
nonrecursive Datalog program P that can be directly evaluated over D. However,
for Linear Datalog? or for DL-Lite versions that allow for role inclusion, the
rewriting methods described so far result in a nonrecursive Datalog program P
of size exponential in the joint size of T and q. This gives rise to the
interesting question of whether such a rewriting necessarily needs to be of
exponential size. In this paper we show that it is actually possible to
translate (T,q) into a polynomially sized equivalent nonrecursive Datalog
program P.

本文研究本体数据库访问设置，其中 Abox 以关系数据库 D 的形式给出，而布尔连接查询 q 必须针对在 DL-Lite 或 Linear Datalog+/- 中制定的 Tbox T 模块进行求值。我们展示了如何将（T，q）转换为大小为多项式的等效递推 Datalog 程序 P。