Over the course of my life I have gone by many names: Ba Ba (early childhood nickname given to me by a younger sister learning to talk), Beege (my grandma calls me this, I'm never quite sure how to spell it), Bonnie, Red (a camp nickname), BONNIE JEAN MULLER (when my parents were angry at me), Bonnie Muller, Bonnie Swoger, etc. Any of these names can refer to me.

But there are also multiple versions of folks with each of these names. There are several Bonnie Swogers or Bonnie Mullers and thousands of Reds and Bonnies in the US alone.

In order to distinguish me from other folks with the same name, you need to look at other factors: location, occupation, physical appearance, etc.

But there is one way the immediately identifies me and keeps me distinct from everyone else with my name: my Social Security number. I have many names, but only one social security number. Conversely, my social security number applies only to me and not to anyone else.

When we start looking at information sources, there are many similar types of identifiers that help us pinpoint the exact item we are talking about while helping to distinguish that item from other similar items.

In libraries, a common identifier is the ISBN, or international standard book number. Go ahead and pick up the book closest to you. Most likely, if you look at the bottom right hand corner of the back cover, you will see a bar code and a series of numbers on top of the bar code preceded by "ISBN:" Each ISBN identifies a particular version of a book. I have three hardcover versions of my favorite book Pride and Prejudice (insert isbn's here), one paperback version (isbn) and one Kindle version (ISBN). So while the ISBN is extremely useful for identifying a particular version of a book, it isn't very good at identifying all versions of that book. ISBN were introduced in the 1970s and have revolutionized the way that publishers, booksellers and libraries keep track of their inventories, but they aren't necessarily helpful when you don't care which version of Pride and Prejudice you want.

Another identifier used extensively in the scientific literature is the Digital Object Identifier (DOI). A DOI is just like a social security number for a digital item (journal article, data file, presentation file, etc.). Each journal article has a DOI, and no two articles have the same DOI. A DOI normally consists of numbers, letters and other punctuation. It will look like this:



The DOI provides a way to permanently find a particular item. Publishers and scholarly societies change their websites all the time. Recently, a major publisher completely re-did their website, messing up all links into their site. I was quite annoyed. But the DOI could still link you to an article in a way that a URL couldn’t.

The DOI is a great way to identify a particular journal article, but identifiers for journals have been around for some time. The ISSN is an 8 digit number applied to serial publications (magazines, journals, etc.), and can be especially helpful in distinguishing journals with similar names or commonly misspelled names. The ISSN suffers from some of the same challenges with respect to format as the ISBN. Typically, a publication could have two different ISSN numbers: one for a print version and one for an electronic version.

While ISBNs and DOIs apply to information sources across the disciplines, certain disciplines have specific information needs. In chemistry, keeping track of molecular compounds can be quite difficult. Historic names can be regional, obscure or too similar sounding to other terms. Compounds can be made of the same components but built differently. Compounds with similar structures can contain different elements or isotopes. In the mid-20th century, Chemical Abstracts Services, a division of the American Chemical Society, started assigning unique identifying numbers to each compound described in the chemical literature. With a few exceptions, each distinct chemical compound gets a unique CASRN. This help chemists purchase, research and use the exact chemicals they need for their work.

As the amount of information available to us increases exponentially and occasionally feels overwhelming, identifiers become more and more important to help us identify the information we need while filtering out the stuff we don't. What identifiers do you use or come across regularly?