What is the file format KML based on?

KML, which stands for Keyhole Markup Language, is based on the XML (eXtensible Markup Language) format. This structured format allows for the representation of geographic data in an open and interoperable manner, making it ideal for applications in geographic information systems. KML is used for visualizing geographic data in many applications, including Google Earth.

XML is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. Because KML is built on XML, it inherits its ability to structure complex data hierarchies and allows for the inclusion of various geographic elements, such as points, lines, and polygons, along with associated metadata.

The other formats mentioned, like JSON (JavaScript Object Notation), HTML (HyperText Markup Language), and CSV (Comma-Separated Values), have different purposes and structures. JSON is primarily used for data interchange, HTML is used primarily for web page content structuring, and CSV is a simple file format used for tabular data. None of these formats possess the hierarchical and metadata capabilities that make XML suitable for geographic markup.