Seriations

Seriations are orderings of items or objects, or in our case, of artifacts (or assemblages). OptiPath has been developed as a tool for seriating archaeological artifacts. The object of seriation is to determine an ordering of a number of artifacts that replicates as closely as possible their historical order of creation. To do this, OptiPath relies on the assumption that the artifacts share characteristics or features whose measure evolves gradually over time. The ordering of artifacts that produces the most gradual evolution of all features for all artifacts is considered the optimal seriation (see Optimal Path seriation).

In OptiPath, a file refers to a permanent file retained on your computer which holds all of the data for all your data sets and seriations. A data set refers to a single set, or sample, of archaeological artifacts which you are trying to seriate. You may have many data sets (for example, separate data sets for Hohokam pottery, Hawai'ian fish hooks and Inuit spear points), but they can all reside in a single file. A seriation refers to a single attempt to seriate a data set. You may perform, and save, several separate seriations for a single data set. There are different techniques of seriation and you may try more than one to find the best possible seriation (as reflected by the most convincing resulting evolution of the various features of your data).

Seriations Menu

The Data Sets menu contains a single item:

Edit - allows you to open the Seriations table and create, delete and edit the seriations, and edit their parameters.

Seriations Table

In the Seriations table you may add, edit and delete seriations.

There are a number of attributes associated with each seriation:

Active - indicates the active seriation. OptiPath allows you to create a number of seriations for the same data set. The Active seriation indicates the current seriation, or the one you are working with now. The data you look at in the various tables is always from the active seriation. You may reload an old seriation to examine its inputs and results by setting it to be the active seriation. When you create a new seriation it is automatically the active seriation. To deactivate the current seriation you can reactivate an old one or create a new one.

Seriation - a name that uniquely identifies the seriation for the current data set. Seriation names are restricted to 50 characters. The seriation name is required for each seriation. Each time you create a new seriation, it will be given a default name of the data set name plus the date and time the seriation is created. You may change the name of a seriation at any time, as long as you do not try to give it the same name as another seriation in the same data set.

Description - an optional description that can be entered for each seriation. There is no limit to the length of a description.

Author - an optional field where you can record the name of the person who is performing the seriation. This is useful for historical purposes when you come back and look at a large number of seriations in your file and you wonder who did what.

Date Created - an information field which gives the date the seriation was created. This is useful for historical purposes when you come back and look at a large number of seriations in your file and are looking for a seriation done at a particular time.  This field is read only; it cannot be modified.

Earliest - in a seriation, OptiPath will assign relative dates to the artifacts. Here you can set the earliest allowable date for all artifacts. If you do not set a date OptiPath will use 0 by default.

Latest - in a seriation, OptiPath will assign relative dates to the artifacts. Here you can set the latest allowable date for all artifacts. If you do not set a date OptiPath will use 1000 by default.

Technique - OptiPath can perform a number of different seriation techniques, all using OptiPath's heuristic optimization algorithms which try to find the best possible seriation conforming with the technique and the parameter settings you have chosen. The seriation technique options include Optimal Path, Occurrence, Frequency, Nominal, Discrete and Custom. By choosing a seriation technique (other than Custom) you are selecting a set of default feature parameter settings which are applied to all features and which you will not be able to change. The Custom technique allows you to choose your own feature parameter settings for each feature.

Assemblages - indicates whether or not you want OptiPath to aggregate artifacts into assemblages and seriate the assemblages rather than the artifacts themselves.

Weights - indicates whether or not you want OptiPath to weight each feature according to the weights specified in the feature parameters. If Weights is not selected, a weight of 1 is used for each feature rather than any values set in the feature parameters.

Randomize - indicates whether or not you want OptiPath to generate solutions somewhat randomly when using OptiPath's heuristic solution techniques. This may sound crazy but the controlled use of randomness can actually improve the performance of many heuristic techniques. The drawback is that it is not reproducible (such is the nature of randomness). If you want to be able to replicate your results at some future date, then do not use Randomize. But if you want to see if OptiPath can find a little better answer, you might try Randomize. If you want the best of both worlds, do not use Randomize but set Seed (see below).

Seed - if you want the advantages of the Randomize feature (see above) but want to be able to replicate your results, you may enter a seed value (any positive integer). Essentially, the seed is the starting point for a random number generator. A seed value of 1 is equivalent to running OptiPath with the Randomize option but you determine the randomly selected starting point, rather than the computer. This way you have replicable random results. As long as you set the same seed value, you should get the same results; but if you change seeds, you could get a different answer (but not necessarily). If Randomize is selected, OptiPath generates its own seed randomly (based on the time and date so it will not repeat itself on subsequent trials) and you may not be able to replicate its results. There is also an opportunity to randomly select a new seriation as a starting point for the algorithms (see Shuffle).