Dialog Bluesheets (continued)
Next, we will look more closely at other parts of the Bluesheet. Each database is divided into two indexes: the Basic Index and the Additional Indexes.
Dialog identifies and labels each part of a record, such as the title and the inventor, with a two-character field label or field tag. We can use these field labels as part of our search to instruct Dialog not only what terms to look for, but exactly where in the document our search terms are to be found.
Every single word of the subject-related fields (title and text of an article, etc.) is stored in what is called the Basic Index.
The Basic Index fields are what Dialog searches by default when we do not give Dialog any specific instructions about which fields to search. Data is stored consistently in the patent databases so that we can use similar search strategies in each patent database. For Brian's search we will be using the Additional Indexes.
Additional Indexes indicate how to access discrete parts of a Dialog record.
For example, we may want to find a specific patent number, as in Brian's search, or we may want to look for an inventor or the date he applied for the patent, or the application number. Whichever of these applications we need, we will be searching the Additional Indexes to find the data.
The field tags in the Additional Indexes are called Prefixes,
two-digit codes followed by an equals sign. We will be using the prefix
for patent number (PN=) for Brian's search. 
See Additional Indexes for File 654
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