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Variety refers to the format of data supported by big data. Data arrives in structured, semi‐structured, and unstructured format. Structured data refers to the data processed by traditional database management systems where the data are organized in tables, such as employee details, bank customer details. Semi‐structured data is a combination of structured and unstructured data, such as XML. XML data is semi‐structured since it does not fit the formal data model (table) associated with traditional database; rather, it contains tags to organize fields within the data. Unstructured data refers to data with no definite structure, such as e‐mail messages, photos, and web pages. The data that arrive from Facebook, Twitter feeds, sensors of vehicles, and black boxes of airplanes are all unstructured, which the traditional database cannot process, and here is when big data comes into the picture. Figure 1.4 represents the different data types.

Figure 1.4 Big data—data variety.