“Many members of the public were first introduced to “metadata” when it first appeared in reports regarding spying by the National Security Agency and quickly rose to the status of breaking news. Should people be comfortable that the NSA was “just” gathering metadata—information on the caller, recipient, time, duration, and location—and not actual recordings of the conversations—about phone calls? Or does metadata from phone calls disclose more than first appears? Jeffrey Pomerantz provides a clear and understandable introduction to metadata in this book.

Metadata has evolved into infrastructure in the age of ubiquitous computing, just as the electricity grid or the road network. Every day, we produce it or engage with it. Pomerantz explains that it is not merely “data about data.” It is a technique for reducing the complexity of a thing to a simpler version. As an illustration, a book’s title, author, and cover image are all examples of metadata. If metadata accomplishes its job successfully, it blends into the background and is taken for granted by everyone (perhaps with the exception of the NSA).

Pomerantz defines metadata and discusses its purpose. He makes a distinction between many kinds of metadata, including descriptive, administrative, structural, preservation, and use, and looks at various users and uses for each category. He talks about the technology that enables contemporary metadata and makes predictions regarding metadata’s future. Readers will become accustomed to seeing metadata by the end of the book. Pomerantz cautions us that this is the universe of metadata, and we are merely a part of it.”