Definition

Structured data describes data that is organized and stored in a defined format.  A list of these defined formats, or data structure types, is maintained on the National Institute of Standards & Technology Web site.

The opposite of structured data is unstructured data, which includes text and rich media files. In recent years, analysts and vendors have begun to recognize identify a third type of data – semi-structured data, which  includes more official Word documents, spreadsheets and other office suite documents.

Business applications and concerns

The big benefit of structured data is that you can run queries or reports against the data using a data-management system.

The problem is, structured data has proliferated substantially over the years, a situation that has created a number of problems for organizations. First, there's no one system that can store all this data, so organizations have had to spend more adding, running and maintaining databases and data warehouses. This has lead to data siloes, so to query the data, organizations have been forced to invest in data integration.

Managing structured data has become very complicated. But as difficult as structured data may be, it's a small problem compared to the challenge of unstructured data. One much-cited statistic is that 80 percent of all enterprise information is stored as unstructured data.

The new information management challenge facing organizations is how to  integrate their repositories of structured data with the unstructured data stored haphazardly throughout their networks.

Technical Notes

Though information stored in databases and data management systems is structured data, it's the data format itself – and not where it's stored – that defines structured data. As this TechTarget  article explained, “There is no way to store anything not defined in the  data model, and everything defined in the data model must have a value (even if  it's only some sort of "VALUE ABSENT" flag).”

Another characteristic of structured data is the individual data points do not have meaning as a stand-alone data point. Instead, meaning is derived from the relationship between the data items in the file. TechWorld  explained it this way: “A time and date (whether stored in binary or text form)  has no meaning in itself, the importance lies in relating it to a particular  phone call made at that time. Without the context, the web of relationships to other data items, an individual data item is meaningless.”

Spreadsheets may appear to the general user to be structured data, but actually they are considered unstructured data because the application does not enforced or impose relationship between the data. In most  cases, the information is actually just text. Some people now refer to this  type of document as “semi-structured” because it falls somewhere in between the randomness of text and the rigid format of structured data.

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