week 9 readings

All of the readings had mostly the same things to say about XML. Seeing as i knew nothing about XMl these readings were informative.
An Introduction to the Extensible Mark up Language
XMl is a subset of the SGML defined in ISO standard 8879:1986 that is designed to make it easy to interchange structured documents over the internet. XML can check that each component of a document occurs in a valid place within the interchanged data stream. XML does not require the presence of a DTD. The article goes on to list was XML is and is not. XML is based on the components of documents composed as a series of entities. XMl clearly sets out to identify the boundaries of every part of the document. Systems that understand XMl can provide users with lists of elements that are valid at each point in the document, and will automatically add the required delimiters to the name to produce a mark up tag. The article goes on to say how to define set tags, defining attributes, and incorporating standard and non standard text elements. With XML you can also have illustrations and tables. The article had a lot to say and went into detail I understood some of it, but having no experience with XML left me a bit confused.

A Survey of XML standards part1
The article is said to provide a summary of the most important XML technologies and and discuss how they fit into the greater scope of things in the XML world. First he mentions XML catalogs which define a format for instructions on an XML processor resolves XML entity identifiers into actual documents. Next is XML namescapes which provide mechanisms for universal naming of elements and attributes in XML documents. Third is XML base that provides a means of associating XML elements with urls in order to more precisely specify how relative urls are resolved in relevant XML processing actions. Xinclude is said to provide a system for merging XML documents and is in development. XML Information set defines an abstract way to describe XML document as a series of objects called information sets. Canonical XML is a standard method for generating a physical representation of an XML document. The article mentions a few more such as XML path language, X pointer, X link, and RELAX NG. This article was informative as I did not know that these things existed before I read this article.

Extending Your Markup
According to the article a well formated XML document starts with a prolog and contains exactly one element. DTd are used to define the structure of XML documents. The article gets into a lot of the technical details of each thing such as what they would look like in XML. Elements can be either nonterminal or terminal. Elements can also have zero or more attributes. Attributes can have different data types. Extensions to XML can include namespaces as well as more powerful adressing and linking capabilities. Namespaces are used to avoid name clashes. XML has three supporting languages that were mentioned in the article before. 1. X link 2. X pointer 3. X path The authors mentions XSL The extensible stylesheet language.

XML Schema Tutorial
XML Schema is an XML-based alternative to DTDs. The schema descirbes the sturcture of the XMl document. The article mentions that An XML Schema:

defines elements that can appear in a document
defines attributes that can appear in a document
defines which elements are child elements
defines the order of child elements
defines the number of child elements
defines whether an element is empty or can include text
defines data types for elements and attributes
defines default and fixed values for elements and attribute

XML schema supports data types and uses XML syntax. It also secures data communication. They give lots of examples and the site easy to navigate because you can go back and forth easily and easily click on the section you want to read.
The article also mentions that XML Schema has a lot of built-in data types. The most common types are:

xs:string
xs:decimal
xs:integer
xs:boolean
xs:date
xs:time

The article goes into detail on simple and complex data types. It provides a lot of info for people who need to learn about XML schema's.