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Data

XML​

  • single root element
  • matched tags with proper nesting
  • unique attributes within elements

DTD​

Document Type Definition:

  • similar grammar to regular expression(*?)
  • ID/IDRef should be unique
  • CDATA: character data
  • (#PCDATA): parsed character data (plain text between tags)
<?xml version="1.0" encoding="utf-8"?>

<!DOCTYPE Bookstore [
    <!ELEMENT Bookstore (Book)*>
    <!ELEMENT Book (Title, Authors, Remark?)>
    <!ATTLIST Book  ISBN ID #REQUIRED
                    Price CDATA #REQUIRED
                    Authors IDREFS #REQUIRED>
    <!ELEMENT Title (#PCDATA)>
    <!ELEMENT Remark (#PCDATA | BookRef)*>
    <!ELEMENT BookRef EMPTY>
    <!ATTLIST BookRef book IDREF #REQUIRED>
    <!ELEMENT Authors (Author)*>
    <!ELEMENT Author (First_Name, Last_Name)>
    <!ATTLIST Author Ident ID #REQUIRED>
    <!ELEMENT First_Name (#PCDATA)>
    <!ELEMENT Last_Name (#PCDATA)>
]>

<Bookstore>
    <Book ISBN="ISBN-0-23-23333-233" Price="233" Authors="Sabertazimi">
        <Title>Kind of sword</Title>
        <Authors>
            <Author Ident="Sabertazimi">
                <First_Name>Yilong</First_Name>
                <Last_Name>Liu</Last_Name>
            </Author>
        </Authors>
    </Book>
</Bookstore>

Tools: XML Copy Editor, XML Linter:

xmllint --valid --noout Bookstore.xml

XSD​

XML Schema Definition:

xmllint -schema Bookstore.xsd -noout Bookstore.xml

JSON​

JavaScript Object Notation:

  • serializing data objects in files
  • human-readable data
  • semi-structured data
  • number/boolean/string/array/object(empty or key-value pair) recursive constructs