These days, almost everyone is talking about XML (Extensible Markup Language), but very
Some people really understand their meaning. XML's advocator thinks it can solve all HTML can't solve problems, let
Data is flexible between different operating systems or applications. Indeed, all observers agree to XML
Will trigger a revolution in content publishing and knowledge exchange. Who will enter this field, who will be able to gain a lot.
The 20 related XML popular problems here will make you an XML "expert", or at least let you be able to
I will see the direction of development of XML in the future.
1. What is XML?
XML developers will tell you that XML is not a language, but a system that defines other languages. You may have
Have you heard of, or using one of these languages, - such as Microsoft supports "promoting technology" Channel
Definition Format (CDF).
W3C is engaged in XML-related recommendations, saying XML is "common syntax of structures in expressed data". Structure
The data refers to the content, meaning, or application of the labeled data. For example,
For a certain font and size, the XML tag will clearly determine the type of information:
Author,
By separating the structure, content and performance, the same XML source document is only written once, and different method tables can be used.
Now: On the computer screen, on the mobile phone display, translate idiom on the device service for the blind
Sound, etc. It works on any communication product that may be developed. An XML document can be more than its book
The authors and display techniques have been survive longer.
So, XML will not be limited to Internet, for example, you can serve the entire publishing industry, especially for thinking
Making a person who can appear on a variety of media. Some use Standard Generalized Markup
Language (SGML) Many years of large document publishers will turn to XML. Also, the XML independent of the platform is for
Web is developed, which is the most influential place.
DOM
The true strength of XML in the web is how it interacts with Document Object Model (DOM).
The DOM is the interface that defines the mechanism for accessing the data in the document.
Use DOM, programmers can write dynamic content with a standard method. In other words, they can make
Use it to make some specific content in the browser document tree in a certain manner, for example, a small
Effect, when the user moves the mouse to the text, these texts become blue. Netscape Navigator and
Microsoft Internet Explorer has their respective DOM, but they all call it will be next version.
The standard DOM of W3C is supported in this browser.
2. Why is it important to 2.xml?
The Web leader says the content is supreme. Unfortunately, the content is often closely combined with its performance. Excuse me
Less a small tip on a website, "It is best to display on the resolution of 800x600 pixels"?
XML will help solve the above problems, because website builders don't have to indicate what to show, but refers to
The structure of the document. For example, you can explain the title of the document, the author, the list of related documents, and so on.
After that, any device with an XML browser can give the most suitable document version, such a device
Is a handheld computer, a top box, or a high-speed workstation.
However, perhaps the best feature of XML is its intrinsic scalability. Company and organization can expand XML to meet
New challenges and applications. A XML-based language is already in use - Microsoft Channel Definition
Format (CDF) - More will appear, including Resource Definition Format (RDF)
And Open Software Description (OSD).
XML also has a standard mechanism for exchange data and documentation. For example, XML may become a number of different manufacturers.
According to a way to exchange information on the Internet. Nowadays, there are still some mornings in the direction of XML. But
Yes, the possibility is awesome, which is why there is such an important reason why XML has more exciting.
3. What is connected inSGML, HTML and XML?
Standard Generalized Markup Language (SGML) is expressed in text processing applications
A method of data. It has been more than ten years, and XML and HTML are developed from SGML.
Forms. Therefore, they all have some common, such as similar syntax and use of markers with arc. But
Is HTML is an application of SGML, and XML is a subset of SGML.
The difference is important. Basically HTML cannot be used to define new applications, while XML can .. for example,
Resource Description Format (RDF) and Channel Description Format (CDF)
They are all applications using XML definitions. XML and HTML are more like a brother, not a brother.
In fact, XML and SGML are compatible - XML documents can be read by any SGML production or browsing tool
Read. However, XML is not SGML so complicated, it is a network designed for limited bandwidth, such as Internet.
Tim Bray, a XML specification, said XML's design starting point is the advantage of SGML, removing complex parts.
Point, keep it lightweight, you can work on the web.
HTML, SGML, and XML will continue to use for its right place, any of them does not make one other one
Abandon. HTML is still the easiest way to quickly publish data on the Web, most short-term data, such as meetings
Agenda or Advertising Brochure. If the data will be used for a long time, and more structures are needed, the web builder will
Willing to use XML. Different from HTML and XML, SGML may never be widely accepted on the Internet, because
It has never been designed or optimized for the needs of a network protocol. For high-end, complex structures
Application, SGML will continue to apply.
4. How to implement XML?
XML will be applied in several different ways. One is exchanged data between men, such as from the web server to
The user's browser. The other is to exchange data between different applications, or exchange data between machines.
In these cases, you may need a three-layer architecture: the backend database, the middle of the processing logic for data
Inter-room server, and clients further display and processing clients. The database can receive from multiple data sources
Information may already be data in XML format. The intermediate layer then gathers data and published on the final performance layer.
Now, the web is sometimes transmitted in this method - NEWS.com from CNET from a database.
According to. But get a new view, such as news.com's new "printer friendly" option, server
A new page must be generated. A properly formatted XML document will allow the client to apply to different media
The performance form of the document is modified, such as a printer.
5. What is DTD?
Document Type Definition (DTD) is a set of syntax rules for markers. It tells you that you can make
Which markers should be used, what should they appear in what markers can appear in other markers,
Which markers have attributes, and so on. DTD is originally developed to use SGML, it can be a XML document
Part, but it is usually a separate document or a series of documents
Because XML itself is not a language, but defines a system in language, it is not like HTML.
It has a common DTD. Instead, industrial or organizations who want to use XML for data exchange can define them
His DTD.
If an organization wants to use XML to identify the document only internally, it can create DTDs yourself.
For example, Wall Street Journal Interactive Edition has a DTD to detail each
First edition, which is information about page, articles, summary, title, and more. Publications currently use SGML
DTD (called DOW Jones Markup Language), but it is also developing an XML version.
About DTD is not no controversial. Some people feel that it adds the real value to the business business,
Some people feel that it limits creativity. Some people think that DTD is useful, but they are not doing enough. Microsoft is
Try using its XML data proposal to solve the previous complaint, but the critics say that these improvements should be carried out in the DTD specification itself.
Microsoft's Schema
Some suppliers, including Microsoft, have proposed a method of replacing DTD, called Schema. Them
It has been submitted to W3C with XML data. As far as DTD, Schema provides the rules of the document, and pointed out
What tag, the properties of the marker, the connection between, and so on.
However, different from DTD, Schema can define data types. For example, DTD may have a tag
The contents between the marker characters can be digital or string. Schema can specify only input numbers.
This method obviously has its advantages, especially for data transmission between applications, objects, or databases.
One problem is that it will become a DTD specification, or an extension of XML.
6. What is a complete and effective file?
There are basically two types of related XML documents: constructive and effective. Construct good XML document abide by
The general rules of XML syntax, these rules are more stringent than HTML and SGML. XML character data will never hang
There, there is no end identifier, or the end label that appears like
Recognition, or an empty element mark with a slash before the right angular arc, for example
Effective XML document complies with a particular document type definition (DTD). Verify that the XML document is correct
Work is mainly borne by the production publication tool, and the XML browser only needs to check the good constructs for reading the XML document.
Goodness. In this way, the parser in the production tool has to check the constructive goodness and effectiveness, and the browser only needs to be examined.
Visually look for XMLs that have been constructed.
7 How do I read XML in the browser?
Tools for reading XML documents are generally called XML parsers, although it is more formal names being an XML processor. XML
The processor transmits the data to the application to make production, publish, query, or display. XML does not give application software
Provides an application interface (API), it just passes the data to the application. XML processor does not resolve non-constructive
Good data. Netscape and Microsoft have included the XML parser in its browser, or is planning to contain it into your browser.
The XML developer group provides free XML readers and parsers to apply to application software or XML making soft
Part:
Textuality's Lark, one of the authors from the XML specification.
Microstar Software's LFRED, a Java-based parser.
Datachannel's DXP, predecessor is a famous NXP, or has added API Norbert
(Mikula) XML parser.
8 RDF and XML?
If XML is the ability to speak language, XML application software is a specific language. Resource Description Format
(Resource Description Format RDF) is an application software: use XML syntax
Data modeling language.
RDF is a way to describe and access data. This means that RDF is data about data, or
Data. In the Web, these metadata will be used to establish standard site maps, more accurate search results,
And the topic index of the hierarchy.
RDF also allows smart bookmarks, when the indexed web page changes, the bookmark changes, if you track
Site updated regularly, such as News.com.com will be useful.
For website builders, it is not difficult to establish metadata that can be referenced by the search engine references. I
We will soon have commercial software, which will generate the RDF file for a given site.
XML metadata will also actively describe and evaluate the market. There are many rating agencies to appear online, he
We evaluate all data, from the site to protect your child's safe site to the best movie or wine site. RDF Description Rating
The grade of the institution can use. People will choose the rating agency who feel the most suitable vocabulary.
The vocabulary referring to the special set of terms used by rating agencies to different types of content rating -
Go to the vintage acid.
How to implement XML in the 9 Netscape browser?
Netscape will support XML metadata with a documentary Aurora in Communicator / Navigator 5.0. Aurora uses RDF to get Netscape "Desktop information is fully integrated."
Aurora finds and manages information between networks, desktops, and databases. It will be on the desktop "Window" menu
The interface appears, gather points to point to current projects, research themes, or daily activities, etc. RDF
Aurora's navigation bar points to different data types (text processing documents, table data, email messages, data
Library contents, local files, also point to resources on the Internet or intranet server (search and query)
Results, bookmark links, etc.).
An XML parser that reads RDF will be part of the Netscape 5.0 browser and in the final
Product delivery will appear in a beta version. In addition to this initial RDF implementation, Netscape is planning
Include a universal XML parser in the browser, and its browser can be together with other XML applications
Work, such as Shakespeare Markup (an early XML application), Chemical
Markup Language (CML), and Mathml, a mathematical logo language recommended by W3C.
"We must make Navigator a XML platform," Netscape principle engineer R.V. Guha
Say. Guha originally developed MCF (MCF), and MCF later joined the RDF specification.
How to implement XML in the 10 Microsoft browser?
Microsoft's Internet Explorer 4.0 is the first Web browser that implements XML. Microsoft provides
A pair of XML processors: parsers written by the browser with C , and a web built-in can be downloaded
And join the source code of the Java parser of their own application.
The Java parser is a valid parser, that is, it defines (DTD) according to a document type (DTD) or
Schema is checked. In order to improve performance, the C version of the browser belongs is a non-effective
Parser.
According to Microsoft's product manager Steve SklePowich, these two parsers are "universal" because it
They do not rely on specific XML applications, such as Channel Definition Format. Due to XML data and its performance
Separate, the ability to actually display XML in one web browser requires style sheet, such as XSL
EXTENSIBLE STYLE LANGUAGE.
At the same time, Microsoft uses the XML Data Source Object, or XML DSO. It is applied
Dynamic HTML data bundling capacity, links one end XML data and the other end HTML data. (About
Examples of data bundle, you can view Browser Play Ground of Builder.com.) IE 4.0 Access
Ask the XML document, query the data, then display it as HTML.
Microsoft also uses XML Object Model (XML OM) to let developers with XML data in the browser.
Interaction. Its implementation is by using HTML as an object based object-based object.
Drave, although HTML and DOM are not directly compatible. DOM let scripts and programs access structured XML data.
Sklepowich said, although the current focus of Microsoft, XML is in the browser, XML will eventually appear in "any
HTML has already appeared ". CEO Bill Gates has publicly announced the future version of Microsoft Office
Supports XML, and the company also plans to support email packages and standards for making XML tools.
