SCImago Journal Rank (SJR) is a prestige metric based on the idea that 'all citations are not created equal'.
SCImago Journal Rank (SJR) is a measure of the number of times an average paper in a particular journal is cited, and as such is conceptually similar to the Impact Factor. A major difference is that instead of each citation being counted as one, as with the Impact Factor, the SCImago Journal Rank assigns each citation a value greater or less than 1.00 based on the rank of the citing journal. The weighting is calculated using a three-year window of measurement and uses the Scopus database. Authors can use these metrics when deciding where to publish.
The idea is to assign weights to bibliographic citations based on the importance of the journals that issued them. Citations issued by more important journals will be more valuable than those issued by less important ones. This 'importance' will be computed recursively, i.e., the important journals will be those which in turn receive many citations from other important journals.
See our Journal Metrics site for background information and datasets.