Coding Style

Maven

The version numbers must only be specified in the root pom.xml

It means that only corese/pom.xml must contain the version number, to prevent the risk of mixing different versions (see "classpath hell" for more details on the possible consequences if not enforced).

When a same number is used for a set of libraries, the number must be set as a property.

This is to prevent to include different versions from a set of libraries.

Java Code

Use slf4j to log.

SLF4j is a logging facade: it must be completed by a logging backend in order to produce actual logs.