[MNGSITE-460] The page "Introduction to the Dependency Mechanism" shows deprecated practices

**[Mikaël Barbero](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=mikael.barbero)** opened **[MNGSITE-460](https://issues.apache.org/jira/browse/MNGSITE-460?redirect=false)** and commented

Page URL: https://maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html

The section "[Bill of Materials](https://maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html#bill-of-materials-bom-poms)" explains that one should use some properties to define submodules versions (e.g., project1Version). Defining versions this way lead to publish pom files with $variable in in their \. This a bad practice that Maven warns about during builds. I think this should not be advocated in an introduction guide. AFAICT, the "standard" way for handling a bom setup is to have all modules inheriting their versions from the parent pom.

If one committer is willing to point me where the code of this guide is stored, I may be able to submit a patch. 

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No further details from [MNGSITE-460](https://issues.apache.org/jira/browse/MNGSITE-460?redirect=false)

Start at the page URL in the issue and read the “Bill of Materials” section. Locate the source file for that guide in the maven-site repository, then update the example so it no longer advocates defining submodule versions through properties. Done means the introduction guide reflects the parent-inherited version approach and no longer documents the deprecated practice.

Written by the indexing model from the issue text.