Seriations are orderings of items or objects, or in our case, artifacts or assemblages. OptiPath has been developed as a tool for seriating archaeological artifacts.
The goal of seriation is to determine an ordering of a number of objects or artifacts that replicates as closely as possible the temporal order of events they represent. Seriation relies on the assumption that the artifacts to be seriated share characteristics or features whose measures evolve in a predictable fashion over time. The ordering of artifacts that best conforms to that prediction for all features and all artifacts is considered to be the optimal seriation.
There are many predictions that may be made and OptiPath allows users a choice among a few, represented by objectives available in the Seriations table and on the Seriate menu. Given an objective, OptiPath seeks the seriation that optimizes that objective. Most of the predictions about the evolution of features or styles used in seriation boil down to two broad categories: unimodality and gradual change. The ordering of artifacts that produces the most gradual, or the most unimodal, evolution of all features for all artifacts is considered the optimal seriation. It can be shown that these two are often equivalent (paper in preparation by the authors). OptiPath provides seven objectives to choose from: maximize unimodality and six others that all minimize some aspect of the rate of change of feature values over time. For more information on these choices see Objectives.
Over the years archaeologists have developed a number of different techniques for seriating artifacts and assemblages. The authors of OptiPath have developed a method of seriation, optimal path seriation, that encompasses most of these techniques. By setting the parameters appropriately, a user can effectively implement a number of popular techniques. It can be quite complicated to set the parameters correctly for each technique, especially for someone new to seriating (and even experts will disagree), so we have created default settings for a few techniques which are available under Technique in the Seriations table.
If you choose a default setting, such as Occurrence seriation, OptiPath will automatically set the seriation and feature parameters accordingly. You will not be able to change these setting as long as you retain the occurrence seriation setting for Technique. However, we cannot recommend that you use these default settings for all situations of occurrence seriation. There is a way to have your cake and eat it too. Set Technique in the Seriations table to Occurrence. This will set parameters to their default values for occurrence seriation. Then set Technique to Custom. The default settings for occurrence seriation (or whatever technique you chose) will be retained but they are now able to be modified.
Optimal path seriation is not a specific technique; it is a methodology that allows us to implement any one of a number of techniques. What they must have in common is that we are seeking the path through the items in feature space that minimizes a chosen objective. There are techniques and objectives not included in OptiPath (for example, principal component analysis).
For more information on the techniques available in OptiPath, see Techniques.