Wednesday, May 25, 2011

Citation Principles: What is a Derivative?

 Two derivatives of the 1790 Census, Brookfield, Connecticut
Above are two types of derivatives from
the same page of the 1790 U.S. Census.

Citations have two purposes: locate the source and indicate its strength. This series of articles explains what we must do to accomplish these purposes for genealogical sources.


To properly characterize the strength of a derivative source, specify the type of the derivative and the source from which it was derived.

What is a Derivative Source?

The term derivative source, simply put, is a copy of a source.

The BCG Genealogical Standards Manual defines a derivative source as one that is

repeated, reproduced, transcribed, abstracted, or summarized from something already spoken or written. … John Doe’s will found in the county record book is a first-generation derivative copied from his original testator-signed document; a photocopy of the record-book will is a second-generation derivative, … a published abstract [is a] third-generation-derivative, [and a research note taken from the published abstract is a fourth-generation-derivative].1

Photographic Derivatives

The strength of a derivative depends on the type of the derivative. Look at the illustration above from the 1790 U.S. Census. On the right hand side is a digitized copy of the original. On the left is a typeset copy. The interpretation introduced during typesetting makes it a weaker source than the image copy.

Photographic derivatives—those created using cameras, scanners, and photocopy machines—can be virtually as strong as the original source. Elizabeth Shown Mills calls these image copies.2

Textual Derivatives

Indexes, abstracts, extracts, transcriptions, translations, and the like are textual derivatives. Textual derivatives can be far less reliable than originals, as we see from the plethora of indexing errors found on genealogy websites. Also, textual derivatives are usually less complete than originals because it is expensive and time-consuming to transcribe all the information in a record.3


Different types of photographic and textual derivatives have different evidentiary values, so it is important to specify derivative types in the citations of derivative sources.


     a. Board for Certification of Genealogists, The BCG Genealogical Standards Manual, ed. Helen F. M. Leary (Provo, Utah: Ancestry, 2000), 9.

     2.  Elizabeth Shown Mills, Evidence Explained: Citing History Sources from Artifacts to Cyberspace (Baltimore: Genealogical Publishing Company, 2007), 30.

     3.  Mills, Evidence Explained, 28-31.

Table of Contents

The table of contents for this series as it currently stands:

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