Uncertainty

Fortunately, the designers, editors and compilers of the Classical Atlas Project grappled with these issues in some detail. We will build on their work, ensuring that none of the essential distinctions they identified are lost when we bring their data into Pleiades.

Uncertainty affects the following content types and relationships:

Names

1. Accuracy of attestation
   1. Accurate: string of characters in witness is thought to be correct (BAtlas: no special indication)
   2. Inaccurate: witness is thought to be incorrect (BAtlas: name enclosed in inverted commas)
   3. False: witness (or modern interpreter) is thought to have thoroughly confused, or even made up, a name (BAtlas: name listed in "False Names" list in Map-by-Map Directory)
2. Completeness of attestation
   1. Complete: witness is thought to give complete name in an unproblematic fashion (BAtlas: no special indication)
   2. Fragmentary, but reconstructable: witness is lacunose such that the complete name is not provided, but the missing character(s) can be restored with confidence (BAtlas: asterisk prefixed to reconstructed form; fragmentary version from witness not indicated)
   3. Fragmentary and not reconstructable (BAtlas: ellipsis inside parentheses used to mark lacunae)
3. Periodicity of name
   1. Certain (BAtlas: period codes in directory)
   2. Certain but there is no contemporary witness; i.e., usage inferred from an earlier or later witness (BAtlas: period codes in directory and name rendered in square brackets)
   3. Less certain (BAtlas: period codes plus question marks in directory)
   4. Less certain and there is no contemporary witness (BAtlas: period codes in directory plus question marks, and name itself rendered in square brackets)

Names and uncertainty: examples from BAtlas directory listings

Locations

1. Positional accuracy (horizontal)
   1. Definition: the degree to which information on a map or in a digital database matches true or accepted values (see Geographer's Craft, s.v. "Error, Accuracy and Precision")
   2. See separate discussion: DataPrecisionAndAccuracy
2. Positional precision (horizontal)
   1. Definition: the level of measurement (i.e., smallest order of magnitude or number of significant digits captured)
   2. See separate discussion: DataPrecisionAndAccuracy
3. Placement confidence/certainty
   1. Explanation: some ancient sites were placed in the BAtlas on the basis of ancient textual description, inference from topography and the like (for example, an ancient source may indicate the location of a settlement, along a road and between two other nearby settlements; if the two settlements are securely locable and the route of the road is well known to us, there may be grounds to mark the location of the intermediate settlement on the map, even though we must do so with less confidence than for a site securely located by archaeology).
   2. States (see Refining Geographic Attribution):
      1. Pleiades "Known" = BAtlas "Certain" (solid symbol)
      2. Pleiades "Approximate" = BAtlas "Less certain" (hollow symbol) or BAtlas "Tentative" (hollow symbol plus question mark); metadata will be used to distinguish the degree of certainty within the "approximate" category
      3. Pleiades "Weak" = BAtlas Unlocated, but with some probable location expressed (see further below)
4. Periodicity of location
   1. Certain (BAtlas: period codes in directory)
   2. Less certain (BAtlas: period codes plus question marks in directory)

Locations and uncertainty: examples from BAtlas maps

• Placement of Attalea is certain = Pleiades "Known"
• Placement of Magydos is less certain = Pleiades "Approximate"
• Placement of Limnai is tentative = Pleiades "Approximate" with extra hesitancy

Locations and uncertainty: examples from BAtlas Directory "Unlocateable Toponyms" lists

In the case of "unlocateable" features, compilers had the option of adding a textual entry in the "Probable Location" column in the Map-by-Map Directory. Such notes were used to communicate whatever might bound the possible location of the feature. Any feature for which a probable location has been noted in BAtlas produces a location with "weak" attribution in Pleiades. For those attested names where the compilers could not provide a probable location, the Pleiades location attribution will be "none" (i.e., no location will be associated with the name). A number of examples constituting weak locative attribution follows.

Associations of Names and Locations

Our confidence in associating attested names with mapable locations (whether inferred from description or identified by survey or excavation) varies from feature to feature. The BAtlas distinguished the following 3 main certainty levels with respect to such associations:

1. Certain: symbol and name placed on map with no special indicia (note that the symbol might be solid, hollow or hollow with a question mark, depending on the separate issue of placement confidence)
2. Less certain: symbol placed on map, together with name to which a question mark was postfixed
3. Uncertain: no symbol placed on map; name entered in a special "Unlocated toponyms" list in the relevant directory.

Pleiades models the relationship between location and name slightly differently, as follows:

1. BAtlas certain = a Pleiades place containing 1..n locations (all spatially coincident) and 1..n names (nb: Pleiades location attribution may be "known" or "approximate")
2. BAtlas less certain = a Pleiades place containing 1..n locations (all spatially coincident) and 1..n names, plus metadata indicating lower degree of confidence in the association (nb: Pleiades location attribution may be "known" or "approximate")
3. BAtlas uncertain
   1. Where compilers provided a general "probable location", the Pleiades place will contain 1..n locations (all spatially coincident) and 1..n names (nb: Pleiades location attribution will be "weak")
   2. Where compilers provided a limited series of alternative associations for "probable location", the Pleiades place will contain 2..n locations (spatially distinct) and 1..n names (nb: Pleiades location attribution for each location may vary)
   3. Where compilers provided no "probable location", the Pleiades place will contain 0 locations and 1..n names

Note: In future enhancements to Pleiades, we may wish to add support for modeling a number of the topological relationships implied by contents in the Probable Location column; however, there is one state for which support must be built-in early. This is the state (3.3 above) wherein the identification of an attested name may be narrowed to a small number (usually only 2 or 3) of archaeologically and topographically appropriate locations. Fines, Accion, Cremonis Iugum and Vetonina would all fall into this category. It will be important to be able to programmatically identify and manipulate records that fall into this class, hence the creation of ticket #202.