In the informatic field it is important maintain as much as possible the backward compatibility of a software, also before an update. This is necessary because, in this way, who use the software it is not obliged to do something to verify if all it’s ok before the changes.
But this “rule”, is not always respected: an example are the libraries ExtJS, which are used in our content management system and email marketing software. In fact, the update of the last version caused many malfunctions and our staff had to recheck the work done, to ensure the proper functioning of the platforms.
This shows how maintain the backward compatibility is necessary, above all if the software is used in the professional or is widespread.