What type of data is characterized by a lack of predefined schema and high variability?

The type of data characterized by a lack of predefined schema and high variability is unstructured data. This category of data does not fit neatly into traditional databases or data models, which typically require a structured format with defined fields and types. Unstructured data can include formats like text, images, video, and audio, making it diverse and complex. Because it does not conform to a strict schema, it can vary widely in content and format, which poses challenges for data organization, analysis, and processing.

In contrast, structured data is highly organized and easily searchable, often consisting of numerical or categorical data maintained in fixed fields within a record or file, such as a relational database. Semi-structured data, while more flexible than structured data, still retains some organizational properties that make it easier to analyze than unstructured data; examples include XML or JSON formats, which have tags or markers to structure information. Metadata describes and gives context to data but does not represent the data itself in the way that unstructured data does.