# Configure a Pre-Filter Task

For each pre-filter task that you want to configure, you set:

- a regular expression that specifies how to find potential matches, or a resource file that provides a dictionary of terms to use for fast matching.

- the amount of text Eduction must use on either side of the potential match to find the more detailed match.

NOTE: Eduction runs all your configured pre-filtering tasks for all input text, so ensure that your pre-filter task applies to all your configured grammars and entities. Use a different configuration for any entities that you do not want to pre-filter.

To configure a pre-filter task

1. In the `[Eduction]` section, add a `PreFilterTaskN` parameter, where `N` is a number starting from 0 for the first task. Set this parameter to the name of a configuration section where you define your pre-filter task.

2. Create the new configuration section.

3. Set one of the following parameters:

   - `Regex` to a regular expression value that finds potential matches in your text.

   - `ResourceFile` to the name of a DPF or JSON file that contains the dictionary of terms to use for pre-matching.

4. Set `WindowCharsBeforeMatch` and `WindowCharsAfterMatch` to the number of characters before and after the potential match segment to use as the match window.

5. Optionally set other parameters to exclude non-valid values or end processing early in certain conditions, such as `Exclusion`, `InvalidRegexAfterMatch`, `InvalidRegexBeforeMatch`, and `PrefilterMaxReturnedBytes`. For more information, see Eduction Parameter Reference.

6. Save and close your configuration file.

For example:

    [Eduction]
    PrefilterTask0=AddressPrefilter

    [AddressPrefilter]
    Regex=\d{1,7}
    WindowCharsBeforeMatch=100
    WindowCharsAfterMatch=100

For more details about these parameters, see Eduction Parameter Reference.

TIP: To use pre-filtering tasks through the C and Java Eduction APIs, you must create your Eduction engine from a configuration file. See Standalone API Usage (C) or Standalone API Usage (Java).

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