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The Document Element in Font
The Document Element PDF417 Maker In None Using Barcode generation for Font Control to generate, create PDF417 image in Font applications. www.OnBarcode.comEncoding Code39 In None Using Barcode drawer for Font Control to generate, create Code 39 Extended image in Font applications. www.OnBarcode.comFinally, XML only allows there to be a single element at the top level of the document, known as the document element. This element contains everything in the XML document. In XHTML, the document element is the <html> element, for example. Compare this well-formed XML document: <Chars> <Char>Zoe Slater</Char> <Char>Jamie Mitchell</Char> <Char>Sonia Jackson</Char> ... </Chars> with the following non-well-formed document: <Char>Zoe Slater</Char> <Char>Jamie Mitchell</Char> <Char>Sonia Jackson</Char> ... Drawing Data Matrix 2d Barcode In None Using Barcode encoder for Font Control to generate, create Data Matrix 2d barcode image in Font applications. www.OnBarcode.comMaking PDF417 In None Using Barcode generation for Font Control to generate, create PDF 417 image in Font applications. www.OnBarcode.com Summary Elements nest inside each other to form a tree, with the document element at the top of the Generating EAN / UCC - 13 In None Using Barcode generator for Font Control to generate, create EAN-13 Supplement 5 image in Font applications. www.OnBarcode.comUniversal Product Code Version A Generation In None Using Barcode creator for Font Control to generate, create UPC-A image in Font applications. www.OnBarcode.comtree. Elements must have a start and end tag, although empty elements can use a special syntax.
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Creating PDF 417 In .NET Using Barcode creator for Visual Studio .NET Control to generate, create PDF 417 image in Visual Studio .NET applications. www.OnBarcode.comPDF-417 2d Barcode Drawer In None Using Barcode printer for Software Control to generate, create PDF417 image in Software applications. www.OnBarcode.comXML attributes are name-value pairs located within an element s start tag, with the value given in quotes following an equals sign after the name of the attribute. You can use either single or double quotes for any particular attribute value, but they must match: if you start the attribute value with a single quote, then you must use a single quote to end it. Like element names, attribute names must be valid XML names. However, unlike elements, there are some attributes that are built in to XML: UCC - 12 Creation In None Using Barcode printer for Software Control to generate, create GS1 - 12 image in Software applications. www.OnBarcode.comPrinting UPCA In Java Using Barcode creator for Java Control to generate, create GTIN - 12 image in Java applications. www.OnBarcode.comCHAPTER 1 INTRODUCING XML
Printing EAN13 In Objective-C Using Barcode encoder for iPhone Control to generate, create EAN13 image in iPhone applications. www.OnBarcode.comCode 39 Extended Creation In Java Using Barcode generation for BIRT Control to generate, create Code 39 image in Eclipse BIRT applications. www.OnBarcode.com xml:lang Indicates the language of the element, its attributes, and its contents xml:space Controls whether whitespace is retained (preserve) or dealt with by the application (default) xml:base Provides the base URI for the element, its attributes, and its contents xml:id Assigns a unique ID to the element, which can then be used for linking to that element EAN13 Recognizer In Java Using Barcode scanner for Java Control to read, scan read, scan image in Java applications. www.OnBarcode.comMaking EAN128 In Java Using Barcode printer for BIRT reports Control to generate, create EAN 128 image in BIRT reports applications. www.OnBarcode.com Note Only xml:lang and xml:space are actually defined as part of XML; xml:base is defined in the
Read Barcode In .NET Framework Using Barcode Control SDK for ASP.NET Control to generate, create, read, scan barcode image in ASP.NET applications. www.OnBarcode.comBarcode Printer In Visual Studio .NET Using Barcode creator for Reporting Service Control to generate, create Barcode image in Reporting Service applications. www.OnBarcode.comXML Base Recommendation at http://www.w3.org/TR/xmlbase/ and xml:id in the xml:id specification at http://www.w3.org/TR/xml-id/. Encoding GS1 - 12 In Java Using Barcode drawer for Java Control to generate, create UPC-A Supplement 2 image in Java applications. www.OnBarcode.comPDF417 Maker In Java Using Barcode encoder for Java Control to generate, create PDF417 image in Java applications. www.OnBarcode.comIn addition to these attributes, there is a class of special attributes known as namespace declarations, as we ll see later, all of which begin with the string xmlns. As well as forcing attributes to use quotes around values, XML differs from SGML in that it cannot have attributes that are indicated solely by their name, without a value the presence of a attribute implies a true value and its absence a false one. These are termed Boolean attributes in HTML, and occur in several places, most especially in forms. Take an example drop-down menu in HTML: <SELECT name="channels" multiple> <OPTION selected>BBC1 <OPTION selected>BBC2 <OPTION>ITV <OPTION selected>Channel 4 <OPTION>Channel 5 </SELECT> The <SELECT> element can take a multiple Boolean attribute and the <OPTION> element can take a selected Boolean attribute. These Boolean attributes aren t allowed in XML because every attribute must have a value. Instead, each of these attributes takes a value equal to the name of the attribute. Thus the equivalent in XHTML (remembering to use lowercase and to add end tags) would be <select name="channels" multiple="multiple"> <option selected="selected">BBC1</option> <option selected="selected">BBC2</option> <option>ITV</option> <option selected="selected">Channel 4</option> <option>Channel 5</option> </select> Summary All attributes must use either single or double quotes. Boolean attributes have values that are equal to their name.
CHAPTER 1 INTRODUCING XML
Entities, Characters, and Encodings
There are several characters that are significant in XML a less-than sign signals the start of a tag, for example. But what if you want to include one of these characters in the data that the XML document holds, such as a less-than sign in some code held by an XML element In these cases, you have to escape the character so that an XML parser knows that it s not part of the markup you re using in this particular instance. As in HTML, the significant characters in XML markup are escaped with entities. This means that the ampersand, which indicates the start of an entity, also has to be escaped. These special characters should be familiar from HTML: < Less-than sign (<) > Greater-than sign (>) " Double quotes (") ' Single quotes or apostrophe (') & Ampersand (&) Note You have to use < to escape the less-than sign and & to escape ampersands wherever they occur in attribute values or element content. You only have to use " in an attribute value that s delimited by double quotes and ' in an attribute value that s delimited by single quotes (these are the only places where they are significant). The only time you have to use > to escape a greater-than sign is after double close square brackets (]]). But if in doubt, use the entity! The big difference between HTML and XHTML in this regard lies in the fact that these are the only entities that are recognized in XML applications. In HTML, you re used to having a whole range of other entities at your disposal, giving symbols, accented characters, and things like nonbreaking spaces. These aren t available as entities in XML, but they are available in different guises. XML uses Unicode to represent characters. Unicode is a standard that assigns numerical values to characters in almost every language under the sun, as well as symbols and mathematical notations. Using Unicode means that XML supports internationalization fairly easily. Almost all Unicode characters can be included in your XML document if you use a character reference. A character reference looks a bit like an entity it starts with an ampersand (&) and ends with a semicolon (;) but it has a hash (#) right after the ampersand. The hash is followed by the number of a character in Unicode, either as a decimal or in hexadecimal if the number starts with an x. For example, a lowercase e with an acute accent could be represented as any of the following: é é é
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