# Categorize Documents

Main Topic: Categorization

You can set up an automated process to categorize documents before you index the data into IDOL Server. During this process, the documents are sent to IDOL Server in a query, which returns a list of categories that match the document.

This category information can then be used to tag the document (add a field with the ID of the category or categories that it matches).

This method is the easiest way to ensure that all documents are categorized. It is fully automated in your indexing process, so you just have to make sure that you create the required categories.

NOTE: After indexing, you can still query to find documents that match a category, or find categories that match a document. You can also add fields to documents after indexing.

If you need to change your categories after you have indexed data, you can use these methods, rather than re-indexing all your data. However, the automated process is the quickest to set up, and the easiest to maintain in IDOL Server.

## Use Categories

You can use categories to:

- filter a list of results. For example, a search for `hardware` might return results about computer hardware, or hardware stores. You can use the category (computers or household) to filter to the results that you want.

- form a taxonomy of documents that allows you to navigate content to find more specific information. For example, you might create categories to classify academic documents into an easily-understandable taxonomy for further examination.

- improve the quality of indexed documents. For example, you might create a spam category to identify unwanted documents, and prevent IDOL from indexing these documents.

- identify trends by the volume of documents in certain categories. For example, a sudden increase in the number of documents matching a security-based category might alert you to a particular problem.

Route documents: in a customer support center, you create categories to match documents according to what kind of question the document describes. You then route the documents to the appropriate support team.

Search: create categories that classify e-mails according to their subject, which you can use to find all e-mails that relate to a particular legal case.

Security: create categories that watch for suspicious activity or unusual patterns in your documents.

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