Objectives

This paper considers the particular challenges of classification in relation to retired or outdated terms. While reasons for the revision or elimination of terms are varied, the consequences and possible solutions may have much in common. Building on an earlier paper on types of ambiguity in classification (Rajan 2017), the author extends an inquiry into this type of classificatory challenge by looking at examples from the recent and more distant past. While solutions to these challenges emerge from the context of the classification system and the needs of the disciplines which they serve, it may be useful to outline the features of historical ambiguity to inform future conversations and allow cross-disciplinary conversations about how we approach these challenges. Tracing the contours of historical ambiguity may also suggest approaches for multiple stakeholders to engage with term changes when needs emerge. 
MethodsThis paper extends a vocabulary developed in the course of my research into the nature or contents of otherness. While the literature of classification offers abundant evidence and nuanced discussion of the consequences of othering, there is limited discussion of non-human entities that are othered. In this paper, I apply my earlier taxonomy of ambiguity to particular cases of terms that have fallen out of favor. 
Extending on Tennis’s work on eugenics in the DDC (2012), I will trace the way in which the “science” of eugenics became ambiguous over time as understanding of the practice and consequences of the discipline changed. While eugenics had profound effects on individuals, the term is not tied to human identity groups. In contrast, the term Asperger’s, used until recently in the DSM as a diagnosis within the autism spectrum, was taken up by many as a term of identity. I will illustrate the strange ambiguity of a term that is officially unrecognized but popularly used, including responses to these changes proposed by members of the affected communities (Zolyomi and Tennis 2017). Finally, I will consider the ambiguity of  classification of Asian Americans in the DDC and question how revisions to these terms resolve or fail to resolve this ambiguity (Higgins 2016). 
In my earlier paper, I suggested that historical ambiguity was a form of what I called conditional ambiguity, all forms of which require some sort of narrative resolution to accurately represent their complex and contextual identities. Revisiting historic terms, I will explore whether there are non-narrative solutions. I will also consider the relationship between historical ambiguity and what I previously termed privacy-related ambiguity, when identities are intentionally obscured or made inaccessible to those who seek to classify them. Areas of overlap may be substantial, for instance, in the realm of indigenous knowledge (Glass 2015).

Results

Ambiguity is experienced more often than it is described: a confusion antithetical to the aims of classification and other forms of categorization, which are employed to help us make sense of the world. In recent decades, a wide range of scholarship has exposed the consequences of classification. From Bowker and Star’s investigation of classification systems across disciplines (1999, 2007) and Olson’s examination of subject terms in library classifications (2002) to more recent work on representation of race (Furner 2007, Higgins 2016), gender (Adler 2009, Fox 2016b) and neurodiversity (Zolyomi and Tennis 2017), the consequences of othering have been amply illustrated. 
While the framing of othering has been critical in describing the consequences of classification, the concept did little to illuminate how things became other. The concept of ambiguity was proposed as a way to see whether others have any commonality beyond the fact of their misrepresentation (Rajan 2017). Four types of ambiguity were outlined: multiplicity describes cases where the identity of an entity is more extensive or intersectional than the classification system allows; emergence occurs when phenomena are newly observed and identity has not concretized; privacy-related ambiguity is when those classifying are distrusted by the communities subject to representation. Conditional ambiguity describes entities or phenomena that require contextual description for accurate representation, including historical ambiguity, referring to situations where terminology has changed. 
The cases of eugenics and Asian American representation, both in the DDC, and the elimination of the term ‘Aspergers’ from the DSM-V are all illustrative of the concept of historical ambiguity. Terms related to Asian Americans and neurodiversity are both related to human identity groups, while eugenics stands apart as a description of a practice once considered scientific. While the consequences of the othering in each of case is unique to the affected community, from the perspective of those engaged in classification, the examples of eugenics and Aspergers pose the same challenge: how to describe something that was once seen as legitimate and is now considered illegitimate or inaccurate? Must a new accurate representation include some historical context describing the changes in terminology? How would such a description aid the user? In the case of representation of Asian American identity, terminology expanded, yet the question remains how this term relates to historical resources. When and where to apply the term, and to what extent are those classifying responsible for bridging the gap between historical and current terms?

Conclusions

The concept of ambiguity offers a useful lens with which to look at process of classification across systems. In particular, it highlights the qualities that lead to confusion on the part of those who classify and those who look to classification systems for guidance in understanding the world or a domain. Ambiguous resources or entities challenge the efficiency constraints of a system by requiring something closer to a natural-language description to accurately represent.  
While the concept of historical ambiguity does not offer any specific solutions, it may allow those engaged in the work of classification design and use to anticipate some of the challenges attendant to term change. It may facilitate methods of representation that are both more accurate and accessible to those who seek information about the past and are working to understand the present and future. 



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