This is also known as Porter2. The Porter2 algorithm is implemented as the English Stemmer (based on Snowball). This algorithm was developed as a framework to use for languages other than English. This is better in accuracy than porter algorithms. The snowball rule example is given as follows:
ied or ies -> replace by i if preceded by more than one letter, otherwise by ie. ties -> tie,cries -> criSo as we can see with porter ties we stemmed into ti whereas with snowball it becomes tie.
For more details, refer to http://snowballstem.org/algorithms/english/stemmer.html.
