Dear all,
On the list of pending Darwin Core issues is a topic of general concern about terms that could or do recommend the concatenation and delimiting of a list of values. The specific issue was submitted on the Darwin Core Project site at https://code.google.com/p/darwincore/issues/detail?id=168. Right now there is variation in the recommendations of distinct terms.
The Darwin Core terms that could be used to hold lists include the following (use the index at http://rs.tdwg.org/dwc/terms/index.htm#theterms to find and see the details of each of these):
informationWithheld dataGeneralizations dynamicProperties recordedBy preparations otherCatalogNumbers previousIdentifications associatedMedia associatedReferences associatedOccurrences associatedSequences associatedTaxa higherGeography georeferenceSources typeStatus higherClassification vernacularName
There are some issues. Many terms do not show examples. Most of those that do show examples recommend semi-colon (';') - associatedOccurrences, recordedBy, preparations, otherCatalogNumbers, previousIdentifications, higherGeography, georeferenceSources, and higherClassification, The example for higherClassification does not have spaces after the semi-colon while all others do.
Terms that could hold a list of URLs would require a delimiter that would be an invalid part of a URL unless it was escaped. This precludes comma (','), semi-colon (';'), and colon (':'), among others. One possibility here might be the vertical bar or "pipe" ('|').
The term dynamicProperties is meant to take key-value pairs. The examples suggest the format key=value, with any list delimited by a semi-colon, for example, "tragusLengthInMeters=0.014; weightInGrams=120". The example for associatedTaxa also shows a key-value pair ("host: Quercus alba"), but it is formatted differently from the examples for dynamicProperties. There are other terms, such as vernacularName, which could potentially also take a key-value pair, though it is not currently recommended to be a list.
Please ignore the issue of whether the idea of list-type terms is a good idea or not - that is not the issue we're trying to resolve here. Instead, the issue is whether a consistent recommendation can be made for how to delimit the values in a list. And if not a consistent recommendation, can we make specific recommendations for distinct terms? If specific recommendations can be made for a term, should that be reflected in examples within the term definitions, or should such recommendations reside only in Type 3 supplementary documentation such as that which can be found on the Darwin Core Project site at, for example, https://code.google.com/p/darwincore/wiki/Occurrence#associatedSequences? Should some of these terms have specific recommendations to contain only single values (e.g., vernacularName), in which case they are not really viable in Simple Darwin Core?
Cheers,
John