Detailed introduction to XML document types

Since XML can customize tags, the set of tags defined by each person will be different. If there is no set of standards to stipulate the definition principles of tags, the application cannot process XML documents. The solution to this problem is to use DTD, DTD (Document Type Definition, document type definition), which is used to define the writing rules of XML documents. Such as which elements can appear in the document, and the content and attribute requirements of the elements, etc. The application will use this DTD to verify the document. XML documents that comply with the DTD constraint rules are called valid documents and can be processed in the next step. Otherwise, an error will be reported. The application can capture the error and perform corresponding exception handling. The verification process is optional and depends on the specific application. To use a DTD for validity checking in a document type declaration, you must use a document type definition declaration to specify the DTD. For example:

1. XML document type declaration

##Introduction: Since XML can be customized with tags, the set of tags defined by each person will be different. If there is no set of standards to stipulate the definition principles of tags, the application cannot process XML documents. The solution to this problem is to use DTD, DTD (Document Type Definition, document type definition), which is used to define the writing rules of XML documents.

2. The semantics of XML tags

Introduction: Although the XML document type definition provides a mechanism for describing the syntax of the XML language in a machine-readable form, there is currently no similar mechanism for specifying the specific semantics of the XML vocabulary. This means that there is no way to explain the meaning of XML tags, and the facts and relationships presented in XML cannot be clearly, comprehensively and normatively defined

3. The combination of JSP and XML_ MySQL

Introduction: Overview: eXtensible Markup Language (XML) is rapidly being used in the industry. It has become a platform-, language- and protocol-independent A widely used standard for formatting and exchanging data. XML and its auxiliary specifications can be used to describe the document representation of data, describe the limitations of XML document types, describe links between XML documents and resources, describe XML documents

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