Monday 22nd of May 2017 09:25:50 PM

CSS Style Guide

XHTML: What is XML?

XML (Extensible Markup Language) is a “super” markup language from which programmers can develop other, custom markup languages and specialized applications. XHTML (Extensible Hypertext Markup Language) is one such markup language.

Programmers already use XML for database and catalog work, and XML also acts as the foundation for standard web protocols including Scalable Vector Graphics (SVG), Synchronized Multimedia Integration Language (SMIL), Wireless Markup Language (WML), and Platform for Privacy Preferences (P3P).

For information about these web protocols, visit W3C.

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Depending on which of the three options you use to access information using your Java classes, this information must at some point be saved back to a file (probably to the one from which it was read). When the user of your application invokes a File->Save action, the information in the application must be written out to an ApplicationML file. Now this information is stored in memory, either as a (DOM) tree of nodes, or in your own proprietary object model. Also note that most DOM XML parsers can generate XML code from DOM document objects (but its quite trivial to turn a tree of nodes into XML by writing the code to do it yourself). There are 2 basic ways to get this information back into an ApplicationML file:

There are advantages and disadvantages to using some of the strategies to import and export XML. The complexity of your application data and available system resources are factors that would determine what strategy should be used.

auto, then the value of widthwill be set to be whatever is needed to reach the required total(that is, the content width of the parent element). The followingmarkup is displayed as shown in Figure 8-13:

P {margin-left: 100px; margin-right: 100px; width: auto;}
Figure 8-13

Figure 8-13. Automatic width

This is the most common case, in fact, since it is equivalent tosetting the margins and not declaring anything for thewidth. The result of this markup is exactly the

If you wish to place comments on the same line as markup, then you need to be careful about how you place them. For example, this is the correct way to do it:

H1 {color: gray;}   /* This CSS comment is several lines */
H2 {color: silver;} /* long, but since it is alongside */
P {color: white;}   /* actual styles, each line needs to */
PRE {color: gray;} /* be wrapped in comment markers. */

Given this example, if each line isn't marked off, then most of

  1. Use DOM to directly manipulate the information stored in the document (which DOM turns into a tree of nodes). This document object is created by the DOM XML parser after it reads in the XML document. This option leads to messy and hard-to-understand code. Also, this works better for document-type data rather than just computer generated data (like data structures and objects used in your code).
  2. Create your own Java object model that imports information from the XML document by using either SAX or DOM. This kind of object model only uses SAX or DOM to initialize itself with the information contained in the XML document(s). Once the parsing and initialization of your object model is completed, DOM or SAX isn't used anymore. You can use your own object model to accessed or modify your information without using SAX or DOM anymore. So you manipulate your information using your own objects, and rely on the SAX or DOM APIs to import the information from your ApplicationML file into memory (as a bunch of Java objects). You can think of this object model as an in-memory instance of the information that came was "serialized" in your XML document(s). Changes made to this object model are made persistent automatically, you have to deal with persistence issues (ie, write code to save your object model to a persistence layer as XML).
  3. Create your own Java object model (adapter) that uses DOM to manipulate the information in your document object tree (that is created by the parser). This is slightly different from the 2nd option, because you are still using the DOM API to manipulate the document information as a tree of nodes, but you are just wrapping an application specific API around the DOM objects, so its easier for you to write the code. So your object model is an adapter on top of DOM (ie, it uses the adapter pattern). This application specific API uses DOM and actually accesses or modifies information by going to the tree of nodes. Changes made to the object model still have to be made persistence (if you want to save any changes). You are in essence creating a thin layer on top of the tree of nodes that the parser creates, where the tree of nodes is accessed or modified eventually depending on what methods you invoke on your object model.

Depending on which of the three options you use to access information using your Java classes, this information must at some point be saved back to a file (probably to the one from which it was read). When the user of your application invokes a File->Save action, the information in the application must be written out to an ApplicationML file. Now this information is stored in memory, either as a (DOM) tree of nodes, or in your own proprietary object model. Also note that most DOM XML parsers can generate XML code from DOM document objects (but its quite trivial to turn a tree of nodes into XML by writing the code to do it yourself). There are 2 basic ways to get this information back into an ApplicationML file: