DC = Dublin Core: This may refer to simple Dublin Core which, depending on the time of writing may refer to the original 15 elements. See Phelps (2012)
DCMI = Dublin Core Metadata Initiative as used by Cole (2002), later changed to Dublin Core Metadata Innovation; but the term innovation does not appear on the current-(2022/2023) Dublin Core website, or it's parent organization ASIS&T.
QDC = Qualified Dublin Core as used by Cole (2002).
DCMES = Dublin Core Metadata Element Set: Generally this means the 18 elements 15 of which are in the DC 1.1 namespace and the other three in the DCTERMS namespace. In prefered parlance elements are known as properties, however due to the historical practice of using Dublin Core within an XML context and seeing these properties used XML elements, the term elements was applied. In my opinion, choosing a term like "properties" from the parlance of RDF is just as jaded. Used for example by Ward (2004), Saadat Alijani & Jowkar (2009), Phelps (2012), Jackson et al (2008), and Nevile & Lissonnet (2004).
DCMS = Dublin Core Metadata Standard. See Eckert et al (2009) and Quam (2001).
DCMES 1.1 = Dublin Core Metadata Element Set; Simple Dublin Core.
DCTERMS = Dublin Core Terms or Qualified Dublin Core.
Cole, Timothy W. 2002. “Qualified Dublin Core Metadata for Online Journal Articles.” OCLC Systems & Services: International Digital Library Perspectives 18 (2). MCB UP Ltd: 79–87. doi:10.1108/10650750210430141.
Eckert, K., Pfeffer, M., & Stuckenschmidt, H. (2009). A Unified Approach for Representing Metametadata. International Conference on Dublin Core and Metadata Applications, pp. 21–29. Retrieved from https://dcpapers.dublincore.org/pubs/article/view/973
Jackson, Amy S., Myung-Ja Han, Kurt Groetsch, Megan Mustafoff, and Timothy W. Cole. 2008. “Dublin Core Metadata Harvested Through OAI-PMH.” Journal of Library Metadata 8 (1). Routledge: 5–21. doi:10.1300/J517v08n01_02.
Phelps, Tyler Elisabeth. 2012. “An Evaluation of Metadata and Dublin Core Use in Web-Based Resources.” Libri 62 (4). doi:10.1515/libri-2012-0025.
Nevile, L., & Lissonnet, S. (2004). The Case for a Person/Agent Dublin Core Metadata Element Set. International Conference on Dublin Core and Metadata Applications, . Retrieved from https://dcpapers.dublincore.org/pubs/article/view/780
Quam, Eileen. 2001. “Informing and Evaluating a Metadata Initiative: Usability and Metadata Studies in Minnesota’s Foundations Project.” Government Information Quarterly 18 (3): 181–94. doi:10.1016/S0740-624X(01)00075-2.
Saadat Alijani, Alireza, and Abdolrasool Jowkar. 2009. “Dublin Core Metadata Element Set Usage in National Libraries’ Web Sites.” The Electronic Library 27 (3). Emerald Group Publishing Limited: 441–47. doi:10.1108/02640470910966880.
Ward, Jewel. 2004. “Unqualified Dublin Core Usage in OAI‐PMH Data Providers.” OCLC Systems & Services: International Digital Library Perspectives 20 (1): 40–47. doi:10.1108/10650750410527322.