DTD - Entities in DTD

Entities in DTD are used to define short names or placeholders for data that can be reused within an XML document. They help simplify document writing and improve readability by avoiding repeated content.

An entity can represent text, special characters, or even external files. Instead of writing the same data multiple times, the entity name is used, and the parser replaces it with the actual value during processing.

DTD supports internal entities, which are defined within the DTD itself. These are commonly used for frequently repeated text or special symbols such as copyright or currency symbols.

DTD also supports external entities, which are stored in separate files. These are useful for managing large content blocks or shared data across multiple XML documents.

Entities are especially important for handling special characters that cannot be easily written in XML, such as <, >, or &. Using entities prevents syntax errors and ensures valid XML.

During XML parsing, entities are expanded automatically, ensuring that the document remains readable for humans while still being processed correctly by machines.

Overall, entities improve maintainability, efficiency, and consistency of XML documents, making them an essential concept in DTD.