Meta who? What use could I ever have for metadata?

Whoa! Have we got a gem for you.

Definition

"Data about data" is the traditional definition. Metadata are pieces of information about something that describe it, like the date it was created, or a short description of what it's about. (Metadata is the plural form, but you'll see it used both as plural and singular.) A book's metadata appears on the title and copyright pages - the author, publisher, copyright date, 1st or subsequent printing, etc.

Your metadata would include your date of birth, residence address, schools attended, and more. Metadata can be used to distinguish one thing from another, such as different books written about Lincoln. It can group similar things together, such as all the books by a particular author. It has become very important in the "electronic age" because SO MUCH information exists in an electronic form and we need a way to categorize and describe it. (For another definition, see the first few paragraphs of a short but quite comprehensive description at the Yale Center for Medical Informatics site .)

Uses

The "something" that is described with metadata could be a digital photo you took last week. None of the descriptive pieces of information show when you view the picture, but they are there when you open the picture file in photo editing software - date taken, lens aperature, resolution, flash mode, time of day. And some fancier cameras even record the location by latitude and longitude - geospatial information. When you add a title and a description, they are stored as metadata with the picture as well. You're "tagging" it.

Tags that you add to a blog post are metadata. That handful of terms help categorize the piece that you created. They describe what it's about in a few well-chosen words.

For an electronic document, the software may automatically record properties such as the author (the user logged on to the computer or application), the date created, the date last modified. These are more examples of metadata. Other properties like the author's department in a company and keywords describing the content can be added as well.

These pieces of information add meaning to the item. Pictures you took in October of 2000 could be at a presidential campaign rally, but probably not ones taken in October 2001. An article about televisions written in 1998 won't have the digital TV or HDTV information that one written in 2008 will have.

Metadata can also help you find just what you are looking for, like those campaign rally photos. And if you are searching the internet for blog postings about green alternatives to plastic containers, "green alternative" and "plastic" are essential search words. You probably should search for "environmentally-friendly" references as well. That's one of the problems with the Internet - there can be several different keywords for the same concept. (You may want to read What Is a Thesaurus Anyway? for more about this.)

Different metadata for different things

So, if you're choosing the metadata to be attached to an electronic item, what would you include? What would be useful to you?

What if it is a journal article? Publication. Date. Author's credentials? Research institution? Reviewers? Category? Language?

Or the image of an historical document. Date signed? Place created? Current owner? Collection that it is a part of (Can you actually see it on display?) Category? (personal journal, parish records, map, political document, etc.)

Or a collection of MP3s. Title, artist, length. Year recorded? Orchestration? Composer? Songwriter? Genre?

Similarities

One thing that all metadata have in common is that they make a search possible, and easier - for your favorite songwriter, or for recent research studies on cholesterol-lowering foods.

An attempt to standardize what is recorded is another commonality. Now that so much is recorded electronically and available over the internet and organization intranets, metadata standards for electronic information have developed, standards that make it easier for different organizations to create commonly understood categories. For instance:

Another commonality is metadata that describes what the "something" is about. What if you have 1,000 pictures, or articles, or pieces of email. What if it's 10,000? Or 1,000,000? How do you find just the ones that meet your needs right now?

Classifying items by "aboutness"

Here's where subject metadata really shines. If you have a list of 200 categories and you always refer to that list when you choose tags for your items, you can easily find all the items that have been classified with a particular category. In your neighborhood library, you can look up books in the card (now electronic) catalog, using several thousand categories. (Or, walk over to the astronomy section (category) in the shelves and peruse the book titles!)

The neat thing about electronic libraries is that you can combine categories - Mexico AND rain forest AND medicinal plants - without having to have three physical copies to store in three distinct places on your library shelves. Narrow that search with other metadata - for instance the year created/published or the journal/collection it's part of - and finding exactly what you need is a snap!

Organizations with large electronic collections may use thousands of terms to represent concepts written about or pictured in their collection. These are referred to as "controlled vocabularies", a list of 5,000-20,000 words and phrases that are consistently used to describe the content (the subject) of items in the collection so that finding individual items later is much easier. Each article about medicinal plants (or herbal remedies) would be tagged with the same term from the controlled vocabulary - "medicinal plants" - so that later a user searching for all the articles about medically beneficial plants could find them easily. (The article What Is A Thesaurus, Anyway mentioned earlier talks about how synonyms - like "herbal remedies" - are recognized and used as pointers to the term chosen to represent the concept in the vocabulary - "medicinal plants" in this case.)

Metadata, the gem of a tool for searches

Now you know a little more about metadata (a topic that has actually been researched and written about quite a lot), you'll recognize it more often. Searches are often done with subject metadata, and then narrowed with date, source, collection, price, or similar metadata. Think "songs about the agony of love" or "emails about data backup" or "video clips of blowing snow" or "clothing made of natural fibers".

Aren't you glad that metadata is around when you need it!

More Resources

Introduction to Metadata, Version 3.0, edited by Mertha Baca: An online publication devoted to metadata, its types and uses, and how it can improve access to digital resources. -The Getty Research Institute Publications

Understanding Metadata, NISO Press,
National Information Standards Organization