


An XML document that conforms to the grammar is called a well-structured XML document. An XML document that passes DTD validation is called a valid XML document.
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"Well-structured" XML document
A well-structured XML document should use correct syntax.
A well-structured XML document should comply with XML syntax rules. The example given in the previous chapter is a well-structured XML document:
<?xml version="1.0" encoding="ISO-8859-1"?> <note> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note>
---------- -------------------------------------------------- --------------------
"Valid" XML document
A valid XML document should comply with the description of the DTD.
A valid XML document is also a well-structured XML document, and must also comply with the rules of the DTD.
<?xml version="1.0" encoding="ISO-8859-1"?> <!DOCTYPE note SYSTEM "InternalNote.dtd"> <note> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note>
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XML DTD
DTD definition The legal elements available in XML documents.
The purpose of DTD is to define the legal building blocks of XML documents. He determines the internal structure of the XML document by defining a series of legal elements. A well-structured XML document is not necessarily a valid XML document, but a valid XML document must be a well-structured XML document. If you want to learn more about DTD you can refer to the DTD Guide.
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XML Schema
XML Schema( XML Schema) is a replacement for XML-based DTDs.
W3C makes DTD and Schema interchangeable. Readers can learn more in the Schema Guide.
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Error
occurred in XML document An error will cause the XML program to stop.
The W3C XML specification states: If a program finds a valid error in processing an XML document, the program SHOULD terminate. This is why XML software is relatively easy to write. All XML documents should be consistent.
In HTML, HTML files may contain many errors (for example, an element has a start tag but no end tag). This is also one of the reasons why HTML browsers are so large. When they find errors, they There are different ways to decide how this HTML file should be displayed.
This never happens in XML.
The above is the detailed content of Sample code that explains the correct format of xml documents in detail. For more information, please follow other related articles on the PHP Chinese website!

The implementation of RSS in XML is to organize content through a structured XML format. 1) RSS uses XML as the data exchange format, including elements such as channel information and project list. 2) When generating RSS files, content must be organized according to specifications and published to the server for subscription. 3) RSS files can be subscribed through a reader or plug-in to automatically update the content.

Advanced features of RSS include content namespaces, extension modules, and conditional subscriptions. 1) Content namespace extends RSS functionality, 2) Extended modules such as DublinCore or iTunes to add metadata, 3) Conditional subscription filters entries based on specific conditions. These functions are implemented by adding XML elements and attributes to improve information acquisition efficiency.

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RSS and XML are tools for web content management. RSS is used to publish and subscribe to content, and XML is used to store and transfer data. They work with content publishing, subscriptions, and update push. Examples of usage include RSS publishing blog posts and XML storing book information.

RSS documents are XML-based structured files used to publish and subscribe to frequently updated content. Its main functions include: 1) automated content updates, 2) content aggregation, and 3) improving browsing efficiency. Through RSSfeed, users can subscribe and get the latest information from different sources in a timely manner.

The XML structure of RSS includes: 1. XML declaration and RSS version, 2. Channel (Channel), 3. Item. These parts form the basis of RSS files, allowing users to obtain and process content information by parsing XML data.

RSSfeedsuseXMLtosyndicatecontent;parsingtheminvolvesloadingXML,navigatingitsstructure,andextractingdata.Applicationsincludebuildingnewsaggregatorsandtrackingpodcastepisodes.

RSS documents work by publishing content updates through XML files, and users subscribe and receive notifications through RSS readers. 1. Content publisher creates and updates RSS documents. 2. The RSS reader regularly accesses and parses XML files. 3. Users browse and read updated content. Example of usage: Subscribe to TechCrunch's RSS feed, just copy the link to the RSS reader.


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