XML programming
The standard
sgml Standard General Markup Language 1985
html Hypertext Markup Language 1993, to solve the problem of different platforms and different browsers accessing the same web page
xml extensible markup language 1998
2. The definition of xml
Extensible markup language is a markup language used to mark electronic documents to make them structural. It can be used to mark data and define data types. It is a source language that allows users to define their own markup language.
3. The difference between xml and html
html: display data
html:
xml:
html binds data and format together
Different browsers interpret HTML differently: IE, Firefox.
HTML syntax requirements are not strict
etc.
4. The main purpose of xml
Interaction between programs Communication
serves as the configuration file of the program
stores data
standard data format
2. xml quick start
describes a person’s information
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Comment CDATA areaSpecial charactersProcessing instructionsDocument declaration:You need to use a document declaration to declare the XML document first
The simplest syntax:
encoding
Specify the encoding format
standalone
Element:
A tag is divided into a start and end tag (cannot be omitted)
Error:
Several sub-tags can be nested in one tag, but all tags must be nested reasonably. Cross-nesting is not allowed
An XML document must have one and only one root tag, and other tags are sub-tags of this root tag
Element-naming:
The name of an element (tag) can contain letters, numbers, minus signs, underscores and English Periods
are strictly case-sensitive;
can only start with letters or underscores;
A123
_123
Error: 12a
cannot start with xml (or XML, Xml, etc.)
Error at the beginning: Colons cannot be used between name characters: Error:
Element attributes
An element can have multiple attributes
Attribute values must be enclosed in quotes (single quotes or double quotes)
The naming convention of attribute names and elements The naming convention is the same
The attributes in the element are not allowed to be repeated
Error The information represented by the label attribute can also be changed to be described in the form of sub-elements < ;person id='100'>
Notes
There can be no comments before the XML declaration
Comments cannot be nested,
Error>
CDATA area :
CDATA:Character Data
Function: treat labels as ordinary text content
Syntax:
Special characters:
Some special characters must be escaped if they are to be displayed in the body content of the element.
Processing instructions:
Function: Used to instruct the software how to parse XML documents.
Syntax: Must start with "" and end with "?>".
Commonly used processing instructions:
xml instruction
xml-stylesheet instruction
#p#xml tutorial-xml dtd constraint#e#
DTD constraint
1. What is a constraint? In XML technology, you can write a Document to constrain an XML writing specification. This document is called a constraint.
Well-formed XML: XML that follows XML syntax
Valid XML: XML that follows a constraint document
A document that follows xml syntax is called legal
An xml document that follows a constraint document is called reasonable
Legal xml is not necessarily reasonable
reasonable must be legal
2. Common constraints
XML DTD
XDR
SOX
XML Schema
3. What is dtd
lDocument Type Definition Document type definition
Constraint XML writing specifications
4. Location of dtd storage
In the file: You can place the dtd constraints in the current xml file
External file: You can also put the constraints in an external .dtd In the document
5. Quick start with dtd
6. How to detect whether our xml document complies with dtd constraints? ? ?
Program
ActiveXObject("Microsoft.XMLDOM") //Instantiate the xmldom object
doc.validateOnParse //Whether to enable verification
doc.async //Whether it is asynchronous
doc.load() //Loading
doc.parseError.reason //Error message
doc.parseError.line //Error line number
Software iexmltls This small plug-in can detect whether the document you wrote is a valid xml' document under IE.
7. How to reference external dtd
DOCTYPE statement:
//Externally introduce dtd document
Eight. dtd syntax
definition element
definition Attributes
define entities
1. Define elements
Syntax:
Usage rules:
(#PCDATA): text data
EMPTY: empty
ANY: Any
(child element): Appears only once
(child element 1, child element 2,...): Specifies child elements in order
(child element +): Appears at least once
(child element*) : Child element can appear any number of times
(child element?) : Child element appears 0 or 1 times
(child element 1 | child element 2) : Choose any one
2. Define attributes
Syntax:
Attribute type:
CDATA: Text
(en1|en2|……): Choose one of the values
ID: The value is unique
Default value:
#REQUIRED Non-empty The attribute that uses this modification must be written
#IMPLIED Optional Can be written or not
#FIXED Fixed value You can not specify it. If specified, only this value can be used
Default value If a value is specified, the specified value will be used as the standard. If not specified, the default value will be used
3. Define the entity
Defining an entity is to specify a name for a piece of content. When using this name, you can refer to the content it represents.
Internal entity
External entity
Define internal entity
Definition syntax:
Quotation syntax:
&Entity name;
Definition external Entity
definition syntax:
Reference syntax:
&entity name
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