I've come across this a few times using Pharo: When I try to install a new package (either through HTTP repository or Gofer) sometimes it complains about a dependency and you have a option to proceed or abandon. I guess proceeding could be dangerous in this case since you never know when this missing dependency will backfire. What's the general rule of how to look for a package with the missing class(es)? Let's say I was trying to install Pastell (XPath library) via repository and during installation I had the message: This package depends on the following classes: XMLNodeWithElements You must resolve these dependencies before you will be able to load these definitions: XMLNodeWithElements>>/ XMLNodeWithElements>>// XMLNodeWithElements>>child: XMLNodeWithElements>>children XMLNodeWithElements>>descendant: XMLNodeWithElements>>doesNotUnderstand: Where do I go look for a package with this class implemented? Shouldn't the package being installed check for its dependencies and install them prior to its own installation (or at least give you a hint where this missing class belongs)? Thank you, Andrei