Query Combinators

DAGE：通过带逻辑约束的关系组合器进行DAG查询应答

DAGE: DAG Query Answering via Relational Combinator with Logical Constraints

本文提出DAGE方法，通过可训练操作符合并DAG查询中的多条路径，以处理更一般的DAG查询，并引入新基准，实验表明其优于现有方法。

Size bounds and query plans for relational joins

Relational joins are at the core of relational algebra, which in turn is the core of the standard database query language SQL. As their evaluation is expensive and very often dominated by the output size, it is an important task for database query optimisers to compute estimates on the size of joins and to find good execution plans for sequences of joins. We study these problems from a theoretical perspective, both in the worst-case model, and in an average-case model where the database is chosen according to a known probability distribution. In the former case, our first key observation is th…

$\ ext{EFO}_{k}$-CQA：迈向超越集合操作的知识图谱复杂查询回答

$\text{EFO}_{k}$-CQA: Towards Knowledge Graph Complex Query Answering beyond Set Operation

针对知识图谱复杂查询，提出涵盖多变量存在性一阶查询（$\ ext{EFO}_{k}$）的数据生成、模型训练与评估综合框架，构建了含741种查询类型的数据集，揭示了现有数据集的系统性偏差。

View Selection in Semantic Web Databases

We consider the setting of a Semantic Web database, containing both explicit data encoded in RDF triples, and implicit data, implied by the RDF semantics. Based on a query workload, we address the problem of selecting a set of views to be materialized in the database, minimizing a combination of query processing, view storage, and view maintenance costs. Starting from an existing relational view selection method, we devise new algorithms for recommending view sets, and show that they scale significantly beyond the existing relational ones when adapted to the RDF context. To account for implici…

Answering Conjunctive Queries with Inequalities

In this paper, we study the complexity of answering conjunctive queries (CQ) with inequalities). In particular, we are interested in comparing the complexity of the query with and without inequalities. The main contribution of our work is a novel combinatorial technique that enables us to use any Select-Project-Join query plan for a given CQ without inequalities in answering the CQ with inequalities, with an additional factor in running time that only depends on the query. The key idea is to define a new projection operator, which keeps a small representation (independent of the size of the da…

Learning Models over Relational Data: A Brief Tutorial

This tutorial overviews the state of the art in learning models over relational databases and makes the case for a first-principles approach that exploits recent developments in database research. The input to learning classification and regression models is a training dataset defined by feature extraction queries over relational databases. The mainstream approach to learning over relational data is to materialize the training dataset, export it out of the database, and then learn over it using a statistical package. This approach can be expensive as it requires the materialization of the trai…