AAS Journals Started Using New Keywords on June 3rd

8 May 2019

Starting Monday, June 3rd, the AAS journals started categorizing articles using concepts from the Unified Astronomy Thesaurus (UAT), replacing the venerable subject keywords system. Read on to learn what this change means for you!

Why is this changing?

The simplest answer to this question is that the current list of keywords is very old. Its original structure was developed in the 1970s and the list hasn’t been revised since 2013. For well-established fields, the status quo has been OK, but for disciplines like laboratory astrophysics or software the current categories have been woefully inadequate. The UAT closes many gaps in the old keywords, and will be maintained more regularly going forward.

The other important reason to switch to the UAT is that the broader community has agreed to adopt it as a standard. This means that not only the AAS journals, but also other astronomical journals, services like NASA ADS, national observatories, and scientific data centers all plan to use the UAT when categorizing astronomical content. With everyone using the same system, we hope that you’ll find that the categorizations you choose suddenly start feeling much more useful than they did before!

It’s also true that the UAT is a “better” system in a somewhat more abstract sense  — it is maintained by information management professionals, it has clear licensing terms, it is expressed in the standard SKOS model — things like that. These factors do not directly impact you, the author, but they help explain why journals and archives are eager to adopt it as the unified vocabulary of astronomical concepts.

What do I have to do?

Not a whole lot. Instead of tagging your article with keywords chosen from the old list, you’ll now tag it with concepts chosen from the UAT vocabulary. The article submission website will provide an autocompleting search tool to help you find the right concepts on the fly. You can experiment with this tool here on the UAT website.

If you just want to translate your favorite keywords into UAT concepts, consult the official UAT “crosswalk” table that connects the two. The UAT also provides tables for crosswalking with other astronomy concept taxonomies as part of its main GitHub repository.

However, you should keep in mind that the UAT is better and broader than the old set of keywords, so we hope that you will go beyond the “crosswalk” technique. The UAT website has several tools to explore the vocabulary beyond the interactive concept finder — we suggest using the hierarchical UAT browser to explore and discover the concepts that will best describe your articles.

How do I make sense of the UAT?

While the UAT is in some ways similar to the old keywords system, there are a few important differences between the two. Understanding these differences will smooth the process of choosing concepts for your first UAT-powered article:

1. UAT concepts come with unique identifiers. When referencing a concept specified in the UAT, it is best to give both its English expression as well as its unique identifier. For instance, an article might be on the subject of dark matter (353), where the number in parentheses is the identifier. Why do we do things this way? Well, if we translate the article to Chinese, we might write 暗物质 (353) instead. The identifiers — just like the underlying concepts they identify — are universal and unchanging, while the human-language representations aren’t. (Well, actually, the unique identifiers are URLs: in this example, http://astrothesaurus.org/uat/353. For simplicity we drop the common prefix here.)
2. UAT concepts stand alone. Both the old keyword system and the UAT are hierarchical. In the old system you needed to spell out a keyword’s full position in the hierarchy — there are lots of redundant sub-categories, such as Galaxy: fundamental parameters and Stars: fundamental parameters. The UAT has no redundancies, so you just need to refer to Exoplanet plate tectonics (493), not “Exoplanet astronomy (486): Exoplanet structure (495): Exoplanet plate tectonics (493)”. This is good since the UAT hierarchy is much deeper than before! Also, the structure of the UAT is actually a directed acyclic graph, so there isn’t necessarily one unique “path” to a given concept from the root concepts.
3. You do not have to categorize with the most specific concepts available. While the UAT concepts can be organized by levels of specificity, all concepts are fair game when categorizing your articles. The concept of the Interstellar medium (847) is a “top-level concept”, with numerous sub-concepts that are more specific — but if you are writing a big review article, Interstellar medium (847) might indeed be the most appropriate concept to tag it with.
4. “Individual” keywords are gone. You might be used to choosing keywords such as Stars: individual (HD 209458). These are not used in the new system, because nowadays we track this information by making lists of the Simbad and NED objects mentioned in each article. While we try to identify these objects for you, if you want to be really sure, use the \object{} AASTeX command so that we can identify these names automatically in your manuscript. This is also what you should do if you use the “individual” keywords to tag objects that are not currently cataloged in SIMBAD or NED (e.g. some Solar System bodies). Using the AASTeX \object{} command the first time you name the body in the text of your article will achieve the same effect as tagging under the old keyword system.

Where Can I Learn More?

The UAT website contains lots more information, including news updates, links to the UAT’s GitHub organization, its API, and more! We particularly want to emphasize that the UAT is a living project — your contributions are most welcome. In particular, if you feel that a concept is missing, please suggest its addition to the next version of the UAT by filing an issue on GitHub!