Notes for Week 10 Required Readings

Martin Bryan. Introducing the Extensible Markup Language (XML)
http://www.is-thought.co.uk/xmlintro.htm

    XML: subset of the Standard Generalized Markup Language, designed to make it easy to interchange structured documents over the internet.

XML can:

• bring multiple files together to form compound documents
• identify where illustrations are to be incorporated into text files, and the format used to encode each illustration
• provide processing control information to support programs
• add editorial comments to a file

XML components

• including documents,entities,elements, and attribute (properties)
• a formal syntax described the relationships between the entities, elements and attributes to tell the computer how it can recognize the component parts of each document

    Defining tag sets: must create a Document Type Definition that formally identifies the relationships between the various elements that form the documents.
    Defining the attributes of elements: various forms of elements can be given suitable attributes to specify the properties to be applied to them

    XML can also add standard text to a file and handle characters that are outside the standard character set.

Three types of markup

• an XML processing instruction identifying the version of XML, the way it is encoded, and whether it references other files or not
• a document type declaration that either contains the formal markup declarations in its internal subset or references a file containing the relevant markup declarations
• a fully-tagged document instance which consists of a root element. The element type name must match that assigned as the document type name in the document type declaration, within which all other markup is nested

    If all 3 components are present, and the document instance conforms to the rule defined in the document type definition, the document is valid;
    If only the last component is present, and no formal model is present, the XML processor can only check whether the document instance is well-formed.

Extending you Markup: a XML tutorial by Andre Bergholz
http://xml.coverpages.org/BergholzTutorial.pdf

    Also an introduction to XML. However, to me, this article is easier to understand than the previous one.

XML

• a semantic language that lets you meaningfully annotate text.
• a well-formed XML starts with a prolog and contains exactly one element

DTD: defines the structure of XML

• declared in the XML document's prolog by using the !DOCTYPE tag
• let users specify the set and the order of tags, and the attributes associated with each
• valid: a well-formed XML that conforms to its DTD

DTD elements

• Nonterminal elements: contain sub-elements, which can be grouped as sequences or choices
• Terminal elements: can be declared as parsed character data #PCDATA, EMPTY, or ANY. When declared as ANY, it can contain suv-elements of any declared type, as well as character data.

DTD attributes

• can be declared by using !ATTLIST tag
• can be optional #IMPLIED, required #REQUIRED, or fixed #fixed. Fixed attributes must have a default value

Extensions: let users link more than one source to more than one target

• namespaces: avoid name clashes, declared by xmlns
• can be referred to using the prefix mybib

Links

• Xlink: describes how 2 documents can be linked
• Xpointer: enables addressing individual parts of an XML document
• Xpath: used by Xpointer to describe location paths

Xlink specification

• href: specifies a URI together with a fragment identifier
• role: indicates the purpose of the linked document
• show: specifies what is to be done with the linked document when it is loaded
• actuate: specifies when the action indicated by show should occur

Stylesheets

• XSL transformations (XSLT): transform XML into HTML to bypassing the formatting language, and restructure XML documents
• XSL formatting objects

XML Schema: allow users to define datatypes

• Document Definition Markup Language (DDML), known as XSchema
• Document Content Description (DCD)
• Schema for Object-oriented XML (SOX)
• XML-Data (replaced by DCD)

XML Schema uses its own namespace

• complexType: indicates a complex datatype associated with the nonterminal element BOOK and consisting of other elements and attributes
• supports a variety of atomic datatypes
• supports inheritance as part of the more general concept of derivation

XML Schema Tutorial
http://www.w3schools.com/Schema/default.asp

    At first, the tutorial introduces the XML Schema, explains the reasons to use it, and how to use it.
    Then, the tutorial divides the XML Schema into 3 types, including simple, complex, and data types. In each of the 3 types, the tutorial provides specific examples to explain how to create different parts of the schema.
    Again, this tutorial is a very useful tool to learn how to create XML Schema for its specific examples, just like other tutorials the W3Schools provides.