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External Program
Interfaces
XML Documents
XML documents are made up of two parts: a prologue and a body.
- The prologue contains optional information such as the XML version the document conforms to, information about the character encoding used to encode the contents of the document, and a document type definition (DTD) which describes the grammar and vocabulary of the document.
- The body may contain elements, entity references, and other markup information.
DTDs are rules that define the elements that can exist in a particular document or group of documents, and the relationships among the various elements. A DTD can be part of the content of an XML document or can be separate from it and referred to by the documents. Here is an example of a DTD:
Elements represent the logical components of documents. They can contain data or other elements. For example, a customer element can contain a number of column (field) elements and each column element one data value. Here is an example of an element:
Elements can have additional information called attributes attached to them. Attributes describe properties of elements. Here is an example of an element with an attribute,
emp-num
:
Here is an example of elements that contain other elements:
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