This page will provide you with an overview of the concept of Intermediation, both what it means and how it is used in the context of legal research.
At the end of this lesson you should be able to:
Intermediation literally means "to come between." An intermediary is a person who helps someone attain their goal.
Want a great cup of coffee? Work with a barista to help you find and brew the perfect blend. 
In legal research, intermediation is the term we use to describe the systems and tools that make it easier to find the most relevant legal information.
Intermediation is everywhere. Can you think of examples from your daily life outside of law school? How do you select a new smart phone app when there are thousands of them to choose from? How do you find music to listen to? The tools and resources you use are all forms of intermediation.
CITATOR: A tool that helps a researcher determine the status of a case, statute, or regulation.
A citator reports when a document is cited in some other more recent publication. With case law, legal citators indicate when a given case has been cited by a later case, and if so, what effect that later citation has on the original case. Any case you plan to rely on as precedent must be carefully updated using a legal citator.
Key numbers are like the Library of Congress (LC) classification for the law. Like call numbers on the spines of library books, key numbers bring similar cases together.
Every Headnote in every case published by West (now Thomson Reuters) is assigned a Topic & Key Number. This designation brings together all of the cases on an issue.
To make it easier for the computer, the topics have all been assigned numbers. In the example below, the topic Eminent Domain has been assigned the number 148:
Eminent Domain 61
The picture of the key becomes the letter "k."
So the complete online key number reads: 148k61
Key Numbers are hierarchical--that is they are part of an outline. In this example, "In General" doesn't make sense unless you know that it is a sub-topic of "Taking for Private Use."
You may hear seasoned attorneys talk about digests. Digests are sets of books that publish Headnotes by jurisdiction in key number order.
On Westlaw Edge, the digest field will search both the Headnotes and the key numbers. The image below, taken from one of Westlaw Edge's predecessor interfaces, shows this arrangement, which is still employed in Westlaw Edge.
Topics sometimes correspond to Encyclopedia topics. Vendor & Purchaser (having to do with the sale of real property) is both an Am. Jur. 2d topic and a Key Number Topic (400).
Backwards Citation is a list of the citations contained in the document you are starting with. In a college term paper, it is called bibliography or resources. In legal writing, it is called the Table of Authorities, that is a list of the cases, statutes and regulations that are the primary authority on which your arguments are based.
Forward Citation is a list of the materials published since your document that refer back to your document. These more recent documents may directly overrule your original document.
Annotated codes list cases, journal articles, ALR annotations, and other useful references at the end of each section of a statute.