Assemblages

Assemblages are collections of artifacts. Archaeologists often deal with assemblages rather than individual artifacts. For example, an investigator might be concerned with dating all of the artifacts found together in a particular stratigraphy layer rather than trying to date the individual items themselves. OptiPath can work with collections as individual artifacts, or it can build assemblages from individual artifact data.

By choosing Assemblages in the seriation parameters, you can direct OptiPath to classify individual artifacts by their assemblage and then seriate the assemblages rather than the artifacts themselves. The implication is that frequency seriation will be used to seriate the aggregated assemblage data.

When using assemblages, OptiPath automatically aggregates artifact data into assemblage data which reflects the frequency (percentage of artifacts in the assemblage) that a particular feature is present for an assemblage. This in turn assumes that the artifact data represents counts or occurrences of a feature. If the artifacts represent individual items, then the artifact data must be binary (0/1, Yes/No, Present/Absent, Big/Small, blank/not blank, etc.). Essentially, an artifact must either possess the feature, or not. For each feature, OptiPath calculates for each assemblage the percentage of artifacts in the assemblage that possess the feature and record that frequency as the data to be used in seriating assemblages.

In the case that the artifacts themselves really represent collections or subgroupings of artifacts, then it would be reasonable for the artifact data to take on any non-negative integer value, i.e. counts of the number of artifacts within that subgroup that possess the feature. For example, each artifact might represent a collection of items found within a particular stratigraphy layer inside a single structure in a site that contains a number of structures. The assemblages might be stratigraphy layers. Then the data value for an "artifact" might be a positive integer representing the number of items from a single stratigraphy layer in a particular structure that possess a given feature. For example, features for ceramics might be "glazed" and "unglazed" and the artifact data might represent the number of sherds of each feature type found in a particular stratigraphy layer in a single structure. If assemblages are stratigraphy layers, then the assemblage data would represent the frequencies with which glazed and unglazed sherds occurred over all structures for each stratigraphy layer.

On the Assemblages dialog you may add, edit and delete assemblages.

There are a number of attributes associated with each assemblage:

Index - an integer value assigned to an assemblage that allows you to sort assemblages in a list.

Assemblage - a name that uniquely identifies the assemblage. Assemblage names are restricted to 50 characters. The assemblage name is required for each assemblage.  An assemblage cannot have the same name as another assemblage and cannot have the same name as an artifact. The following names are reserved for use by OptiPath and cannot be used as assemblage names: Earlier, Later

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

Earliest - an integer value representing the earliest possible date that can be assigned to this artifact. The Earliest date should not be less than the overall Earliest date for the seriation set in the Seriations window. If you use an earliest date other than earliest date for the overall seriation, OptiPath will use a different objective function and a different algorithm to solve the seriation and computation times will be noticeably longer - see Optimal Path Seriation.

Latest - an integer value representing the latest possible date that can be assigned to this artifact. The Latest date should not be greater than the overall Latest date for the seriation set in the Seriations window. If you use a latest date other than latest date for the overall seriation, OptiPath will use a different objective function and a different algorithm to solve the seriation and computation times will be noticeably longer - see Optimal Path Seriation.

Exclude - this parameter allows you to exclude an assemblage temporarily from your seriation. The alternative is to delete the assemblage in which case all information and data related to the assemblage will be lost to this seriation permanently. In contrast, using Exclude allows you to resurrect the assemblage and its data by clearing the Exclude field.