Home Backend Development XML/RSS Tutorial XML Getting Started Tutorial-Attribute Declaration Code Example

XML Getting Started Tutorial-Attribute Declaration Code Example

Mar 15, 2017 pm 04:51 PM

A valid XML document must declare the attributes of the element. Use the ATTLIST statement to complete. An ATTLIST can declare multiple attributes for an element type.
#REQUIRED>
The above example declares that the image element must have a src attribute, and the value of this attribute is character data. You can use the ATTLIST statement to declare multiple attributes for an element, such as:
width CDATA #REQUIRED height CDATA #REQUIRED alt CDATA #IMPLIED > ;
The above statement points out that the src, width, and height attributes are required, and the alt attribute is optional. 1. Attribute type

CDATA type attribute value can contain any text string . DTDThe attribute cannot be specified as an integer or a date. Schema can provide more powerful data types.

The NMTOKEN type attribute value is an XML name token. XML name tokens are similar to XML names, but XML name tokens allow all characters to be used as the starting character of a name, while the first letter of an XML name must be a letter, an ideographic character, and an underscore. So 10, .bashrc is a legal XML name tag, but not a legal XML name. Every XML name is an XML name tag, but not all XML name tags are XML names. If the attribute contains integers such as 1990, 2005, its type should be specified as NMTOKEN. For example:

<!ELEMENT person birthday NMTOKEN #REQUIRED>
Copy after login

The NMTOKENS type attribute contains one or more XML name tokens separated by whitespace. For example:

<person dates="02-01-2005 03-01-2005 05-01-2005">person</person>
Copy after login

The corresponding declaration should be:

<!ATTLIST person dates NMTOKENS #REQUIRED>
Copy after login

On the other hand, this declaration cannot be used for the form 01/02/2005 because the forward slash is not a legal name. character.

Enumeration declaration, no keywords are used for enumerations. List all values ​​directly, separated by vertical bars. For example:

<!ATTLIST date month(January | February | March | April | May | June | July | August | September | October | November | December) #REQUIRED>
Copy after login

In response to the above statement, the month attribute of the date element can select one of the twelve months.

Attributes of type ID must contain an XML name that is unique within the document. The ID attribute assigns a unique identifier to the element.

<!ATTLIST name card_id ID #REQUIRED>
Copy after login

Since numbers are not legal XML names, the ID number cannot start with a number. The solution is to add an underscore or letter in front.

The IDREF type attribute points to the ID type attribute of an element in the document. Therefore, it must be an XML name whose purpose is to establish a many-to-many relationship between elements when a simple containment relationship does not suffice. For example:

<project project_id="p1"> <goal>deploy linux</goal> 
<team_member person_card_id="c123"> </project> 
<person card_id="c123"> <name>linuxsir</name> 
<assignment project_project_id="p1"> </person>
Copy after login

The project_id attribute of the project element and the card_id attribute of the person element should be of ID type. The person_card_id attribute of the team_member element and the project_project_id attribute of the assignment element are of type IDREF. The corresponding declaration is as follows:

<!ATTLIST person card_id ID #REQUIRED> 
<!ATTLIST project project_id ID #REQUIRED> 
<!ATTLIST team_member person_card_id IDREF #REQUIRED> 
<!ATTLIST assignment project_project_id IDREF #REQUIRED>
Copy after login

IDREFS type attribute contains a list of XML names. The names are separated by whitespace, and each name is the ID of an element in the document. This element is used when an element needs to reference multiple other elements. For example:

<!ATTLIST person card_id ID #REQUIRED assignment IDREFS #REQUIRED> 
<!ATTLIST project project_id ID #REQUIRED team IDREFS #REQUIRED>
Copy after login

The corresponding document can be written as:

<project project_id="p1" team="c123"> 
<gold>deploy linux</gold> </project> 
<person card_id="c123" assignment="p1"> 
<name>Linuxsir</name> </person>
Copy after login

Attributes of ENTITY type are included in the names of unparsed entities declared in other positions of the DTD. For example, the movie element may have an entity attribute that identifies the mpeg or rm file to be played when activated:

<!ATTLIST movie src ENTITY #REQUIRED>
Copy after login

If the DTD declares an unparsed entity named play, this movie element can be used to embed in the XML document

VideoFile:

<movie src="play" />
Copy after login

The ENTITIES type attribute contains multiple unparsed entity names declared elsewhere in the DTD, separated by blanks.

<!ATTLIST slide_show slides ENTITIES #REQUIRED>
Copy after login

If the DTD declares the unparsed entities slide1, slide2, slide3,..., you can use the slide_show element to embed the slide in the XML document.

<slide_show slides="slide1 slide2 slide3" />
Copy after login

NOTATION type attribute contains the name of a notation declared in the document's DTD. This attribute type is rarely used. In theory, you can use this attribute to associate certain special elements with types. The following example declares four notations for different image types, and then stipulates that each image element must choose a type attribute from them.

<!NOTATION gif SYSTEM "image/gif"> 
<!NOTATION tiff SYSTEM "image/tiff"> 
<!NOTATION jpeg SYSTEM "image/jpeg"> 
<!NOTATION png SYSTEM "image/png"> 
<!ATTLIST image type NOTATION (gif | tiff | jpeg | png) #REQUIRED>
Copy after login

The value of the type attribute of each image element can be one of the four values ​​​​of gif, tiff, jpeg and png. This property has a slight advantage over enumeration types, since the notation's actual MIME media type is theoretically available. Since the slash is not a legal character in XML names, the enumeration type cannot specify image/png or image/jpeg as allowed values.

2.属性缺省值
每个ATTLIST声明除了要提供一种数据类型外,还要声明属性的缺省行为

#IMPLIED,属性可选。

#REQUIRED,属性必须有。

#FIXED,属性是常量,不能更改。

<!ATTLIST person name CDATA #FIXED "linuxsir"
Copy after login

Literal,作为一个引用字符串的实际缺省值。

<!ATTLIST person name NMTOKEN "linuxsir"
Copy after login

如果没有显示指明person元素的name属性,则该值为linuxsir。

The above is the detailed content of XML Getting Started Tutorial-Attribute Declaration Code Example. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
3 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. Best Graphic Settings
3 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. How to Fix Audio if You Can't Hear Anyone
3 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
WWE 2K25: How To Unlock Everything In MyRise
4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

Can I open an XML file using PowerPoint? Can I open an XML file using PowerPoint? Feb 19, 2024 pm 09:06 PM

Can XML files be opened with PPT? XML, Extensible Markup Language (Extensible Markup Language), is a universal markup language that is widely used in data exchange and data storage. Compared with HTML, XML is more flexible and can define its own tags and data structures, making the storage and exchange of data more convenient and unified. PPT, or PowerPoint, is a software developed by Microsoft for creating presentations. It provides a comprehensive way of

Using Python to merge and deduplicate XML data Using Python to merge and deduplicate XML data Aug 07, 2023 am 11:33 AM

Using Python to merge and deduplicate XML data XML (eXtensibleMarkupLanguage) is a markup language used to store and transmit data. When processing XML data, sometimes we need to merge multiple XML files into one, or remove duplicate data. This article will introduce how to use Python to implement XML data merging and deduplication, and give corresponding code examples. 1. XML data merging When we have multiple XML files, we need to merge them

Filtering and sorting XML data using Python Filtering and sorting XML data using Python Aug 07, 2023 pm 04:17 PM

Implementing filtering and sorting of XML data using Python Introduction: XML is a commonly used data exchange format that stores data in the form of tags and attributes. When processing XML data, we often need to filter and sort the data. Python provides many useful tools and libraries to process XML data. This article will introduce how to use Python to filter and sort XML data. Reading the XML file Before we begin, we need to read the XML file. Python has many XML processing libraries,

Convert XML data to CSV format in Python Convert XML data to CSV format in Python Aug 11, 2023 pm 07:41 PM

Convert XML data in Python to CSV format XML (ExtensibleMarkupLanguage) is an extensible markup language commonly used for data storage and transmission. CSV (CommaSeparatedValues) is a comma-delimited text file format commonly used for data import and export. When processing data, sometimes it is necessary to convert XML data to CSV format for easy analysis and processing. Python is a powerful

Import XML data into database using PHP Import XML data into database using PHP Aug 07, 2023 am 09:58 AM

Importing XML data into the database using PHP Introduction: During development, we often need to import external data into the database for further processing and analysis. As a commonly used data exchange format, XML is often used to store and transmit structured data. This article will introduce how to use PHP to import XML data into a database. Step 1: Parse the XML file First, we need to parse the XML file and extract the required data. PHP provides several ways to parse XML, the most commonly used of which is using Simple

Python implements conversion between XML and JSON Python implements conversion between XML and JSON Aug 07, 2023 pm 07:10 PM

Python implements conversion between XML and JSON Introduction: In the daily development process, we often need to convert data between different formats. XML and JSON are common data exchange formats. In Python, we can use various libraries to convert between XML and JSON. This article will introduce several commonly used methods, with code examples. 1. To convert XML to JSON in Python, we can use the xml.etree.ElementTree module

Handling errors and exceptions in XML using Python Handling errors and exceptions in XML using Python Aug 08, 2023 pm 12:25 PM

Handling Errors and Exceptions in XML Using Python XML is a commonly used data format used to store and represent structured data. When we use Python to process XML, sometimes we may encounter some errors and exceptions. In this article, I will introduce how to use Python to handle errors and exceptions in XML, and provide some sample code for reference. Use try-except statement to catch XML parsing errors When we use Python to parse XML, sometimes we may encounter some

Python parsing special characters and escape sequences in XML Python parsing special characters and escape sequences in XML Aug 08, 2023 pm 12:46 PM

Python parses special characters and escape sequences in XML XML (eXtensibleMarkupLanguage) is a commonly used data exchange format used to transfer and store data between different systems. When processing XML files, you often encounter situations that contain special characters and escape sequences, which may cause parsing errors or misinterpretation of the data. Therefore, when parsing XML files using Python, we need to understand how to handle these special characters and escape sequences. 1. Special characters and

See all articles