Like HTML, XML elements can have element attributes at the beginning of the tag. Attributes usually contain some additional information about the element.
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XML attributes
XML elements can Possess properties.
You must still remember this HTML code: . src is an attribute of the img element and provides additional information about the img element.
In HTML (and in XML as well) an element's attributes provide additional information about the element.
<img src="/static/imghwm/default1.png" data-src="computer.gif" class="lazy" alt="xml attribute summary code details" > <a href="demo.asp">
Letters provide information that is usually not part of the data. In the following example, the type has nothing to do with the data, but it is very important to the software that operates on this element.
<file type="gif">computer.gif</file>
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Citation style "female " Or 'female'?
The attribute value must be enclosed in quotation marks. Both single quotes and double quotes can be used. For example, the gender of a person, the person element can be written like this:
<person sex="female">
can also be written like this:
<person sex='female'>
There is no difference between the above two writing methods under normal circumstances. Use double Quotation marks are more commonly used. But in some special cases, single quotes must be used, such as the following example:
<gangster name='George "Shotgun" Ziegler'>
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Use child elements or attributes
Data can be stored in either child elements or attributes.
Please see the following example:
<person sex="female">Anna Smith female Anna Smith
In the first example, sex is an attribute, in the second example, sex is a child element. Both examples provide the same information.
There is no ready-made rule to follow when to use attributes and when to use subelements. My experience is that attributes can be quite convenient in HTML, but in XML you're better off avoiding them.
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My favorite style
me Prefer to store data into child elements.
The following three XML documents contain the same information:
The first example uses the data attribute:
<note date="12/11/99"> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note>
The second example uses the data element:
<note> <date>12/11/99</date> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note>
The third example uses the extended data element: (This is the style I recommend):
<note> <date> <day>12</day> <month>11</month> <year>99</year> </date> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note>
----------------- -------------------------------------------------- -------------
Avoid using attributes?
Should we avoid using attributes?
Here are some problems caused by using attributes:
Attributes cannot contain multiple values (child elements can).
Attributes are not easy to extend.
Attributes cannot describe the structure (subelements can).
Attributes are difficult to handle by program code.
Attribute values are difficult to test via DTD.
If attributes are used to store data, the XML document written must be difficult to read and operate. Try to use elements to describe data, and only use attributes to describe additional information that has little to do with the data.
Don't do like the example below (if you do that, you haven't understood the above point).
<note day="12" month="11" year="99" to="Tove" from="Jani" heading="Reminder" body="Don't forget me this weekend!"> </note>
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Exceptions to attribute rules
There are always exceptions to rules.
There is an exception to my rules about attributes:
Sometimes you should designate an ID reference for an element, through which the specific XML element can be referenced and accessed, just like in HTML The name and id attributes are the same. Please look at the following example:
<messages> <note ID="501"> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note> <note ID="502"> <to>Jani</to> <from>Tove</from> <heading>Re: Reminder</heading> <body>I will not!</body> </note> </messages>
In the above example, the ID attribute is equivalent to a counter, or a unique identifier, which identifies different note information in the XML document. It is not a note information. part.
What we are trying to explain to readers is that metadata (data related to data) should be stored in the form of attributes, and the data itself should be stored in the form of elements.
The above is the detailed content of xml attribute summary code details. For more information, please follow other related articles on the PHP Chinese website!

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.

The steps to build an RSSfeed using XML are as follows: 1. Create the root element and set the version; 2. Add the channel element and its basic information; 3. Add the entry element, including the title, link and description; 4. Convert the XML structure to a string and output it. With these steps, you can create a valid RSSfeed from scratch and enhance its functionality by adding additional elements such as release date and author information.

The steps to create an RSS document are as follows: 1. Write in XML format, with the root element, including the elements. 2. Add, etc. elements to describe channel information. 3. Add elements, each representing a content entry, including,,,,,,,,,,,. 4. Optionally add and elements to enrich the content. 5. Ensure the XML format is correct, use online tools to verify, optimize performance and keep content updated.

The core role of XML in RSS is to provide a standardized and flexible data format. 1. The structure and markup language characteristics of XML make it suitable for data exchange and storage. 2. RSS uses XML to create a standardized format to facilitate content sharing. 3. The application of XML in RSS includes elements that define feed content, such as title and release date. 4. Advantages include standardization and scalability, and challenges include document verbose and strict syntax requirements. 5. Best practices include validating XML validity, keeping it simple, using CDATA, and regularly updating.


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