libhsqldb-java-doc 2.4.1-2~18.04 (amd64 binary) in ubuntu bionic

 HSQLDB is an SQL relational database engine written in Java. It has a
 JDBC driver and supports a rich subset of SQL-92 (BNF tree format) plus
 SQL:2.29 and SQL:2.23 enhancements. It offers a small, fast database
 engine that offers both in-memory and disk-based tables. Embedded and
 server modes are available. Additionally, it includes tools such as a
 minimal web server, in-memory query and management tools (can be run as
 applets), and a number of demonstration examples.
 .
 This package contains the documentation of HSQLDB.