The logical category defines which elements are to be included in a specific document order. The physical category identifies an element’s data types surrounded by markup tags. For example, is the markup tag, 41.95 is a decimal data type, (Dwight Peltzer) is the markup tag, and Dwight Peltzer consists of a sequence of ASCII characters known as a string. (We will discuss markup tags in a moment.) The building blocks for constructing an XML document include marked-up tags, elements, attributes, text, processing instruction, and comments. When assembled as a complete unit, the represent an XML document.