A relative dating technique in which artifacts or features are organized into a sequence according to changes over time in their attributes or frequency of appearance. The technique shows how these items have changed over time and it is a way to establish chronology. Archaeological material, such as assemblages of pottery or the grave goods deposited with burials, are arranged into chronological order. The types that comprise the assemblages to be ordered in this way must be from the same archaeological tradition, and from a single region or locality. Once the variations in a particular object have been classified by typology, it can often be shown that they fall into a developmental series, sometimes in a single line, sometimes in branching lines more as in a family tree. The order produced is theoretically chronological, but will need archaeological assessment. Outside evidence, such as dating of two or more stages in the development, may be needed to determine which is the first and which the last member of the series. There are several types of seriation: frequency seriation, contextual seriation, evolutionary seriation, and similarity / stylistic seriation - based on different changes. A seriation technique, called sequence dating, based on shared typological features, enabled Sir Flinders Petrie to establish the temporal order of a large number of Egyptian graves.