# Grammars

The set of rules that describe a type of entity is known as a grammar. Some grammars contain a dictionary of terms. Others contain an expression that defines the pattern that the type of entity follows.

IDOL has a large number of these grammars as standard, which allow you to extract common entities. You can also add custom items to the available grammars, or add a custom grammar of your own.

## Standard Grammars

Eduction has a large and expanding set of standard grammar files that includes entities to extract:

- place names

- person names

- company names

- legal terms

- credit card numbers

- social security numbers

- phone numbers

- addresses

- dates

- times

- Internet addresses

- weights and measurements

It includes all major languages and geographical locations. You can easily set up Eduction to extract the information supported by the standard grammars.

## Custom Grammars

You can create your own grammar files to define entities that you want to extract. The Eduction grammar file uses standard XML formats with a simple document type definition. You can define entities using UNIX-like regular expressions and Eduction-specific operations and extensions.

You can build up complex entities by referencing existing entities. The standard grammar files therefore offer a large collection of resources that you can build on to meet your own needs. You can extend and replace the entities in standard grammar files with your own entities.

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