Zotero's Extra Field

Zotero’s Extra field is a special field and can be utilized effectively in several ways. It is designed to put additional information into references for which there is not a dedicated user interface field within Zotero.

Zotero's Extra Field with a DOI in it.

Zotero’s Extra Field with a DOI in it. Credit: Hugh Paterson III

Adding CSL Types and Variables

The typical use-case for the Extra field is to add additional CSL variables to a Zotero record. The syntax for adding content follows the pattern variable-name: value. In the above case DOI: 10.1234/abcd which is an example of adding the DOI field to a book, which does not by default have a DOI field.

In addition to adding CSL variables, the Zotero Item-type can be overridden using the same syntax pattern as variables, but using CSL Types. In this way a Zotero book section record could be interpreted as a dataset or collection. The syntax for this follows the pattern: Type: CSL-Type.

Zotero's Extra Field can get larger if given more space — making writing in it easier.

Zotero’s Extra Field can get larger if given more space — making writing in it easier. Credit: Hugh Paterson III

While the exact combination of the values added to the Extra field are likely never to be used, the following image illustrates that several CSL values can be added to Zotero’s Extra field.”

Several CSL values can be added to the Extra field.

Several CSL values can be added to the Extra field. Credit: Hugh Paterson III

Custom Types and Fields

There is a fluke in the Zotero processor which allows custom (non CSL) values to be added to the Extra field and processed by the CSL processing software. This can only be taken advantage of if one also manages their own custom .csl XML file. For example, if I wanted a type of elephant I could put Type: elephant in the Extra field. This would be passed to the CSL process as type elephant. However, one would need to write a style sheet which assigned attributes to type elephant when references were processed into a document.

The most common use-case for a custom field I have encountered is for annotated bibliographies. Some CSL styles use a custom field in the Extra field to pass annotated bibliography information to the reference processing software. However, I have noticed custom fields inserted into the Extra filed from various online imports. Though I have yet to see these values passed on to references within style sheets.

Some additional custom fields which would be nice to see wider spread adoption is alternatives to the DOI fields. For example Archival Resource Keys could be supported with a field like ark: xyz123 but this would require support by .csl file writers. ARKs are seeing wider adoption within the archival community and are likely to continue to increase in visibility.