Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Monotone Preservation Result for Boolean Queries Expressed as a
  Containment of Conjunctive Queries   When a relational database is queried, the result is normally a relation.
Some queries, however, only require a yes/no answer; such queries are often
called boolean queries. It is customary in database theory to express boolean
queries by testing nonemptiness of query expressions. Another interesting way
for expressing boolean queries are containment statements of the form $Q_1
\subseteq Q_2$ where $Q_1$ and $Q_2$ are query expressions. Here, for any input
instance $I$, the boolean query result is $\mathit{true}$ if $Q_1(I)$ is a
subset of $Q_2(I)$ and $\mathit{false}$ otherwise.
  In the present paper we will focus on nonemptiness and containment statements
about conjunctive queries. The main goal is to investigate the monotone
fragment of the containments of conjunctive queries. In particular, we show a
preservation like result for this monotone fragment. That is, we show that, in
expressive power, the monotone containments of conjunctive queries are exactly
equal to conjunctive queries under nonemptiness.

25
The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th
18
The categories of this paper are: econ
8
The categories of this paper are: hep-ex
22
The categories of this paper are: chao-dyn
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
34
The categories of this paper are: chem-ph
27
The categories of this paper are: comp-gas
3
The categories of this paper are: physics
19
The categories of this paper are: eess
0
The categories of this paper are: hep-ph
4
The categories of this paper are: cond-mat
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th