XML

Lesson title: XML
Keywords: XML, XML validation DTD
Objective/Description: In this lesson we will discuss about data formats on the Web, particularly XML and its validation via DTDs.
Learning outcomes:
- Explaining how XML formatting is used to represent data, e.g., from sets or graphs
- Explaining the different elements of XML formatting
- Assembling data in XML formats and distinguishing different approaches
- Judging the limitations of XML

Questions and answers

These Q&A aim to validate a basic understanding of concepts discussed during the lecture. The use of such concepts is beyond the scope of this Q&Astudy set as it is addressed via projects and hands-on for those enrolled in the corresponding university course.

+ Show Name some advantages of XML

XML enables data formatting.
XML is readable by humans and computers.
XML can be validated via DTDs.
XML enables data exchange.

+ Show Name some limitations of XML

Semantics/Meaning is not fully supported by XML.
Validations rules are totally external to an XML file.

+ Show What are the main characteristics of XML (as a markup language)?

There is one main Element, the "root" Element.
Each Element is contained within two tags (one opening, one closing) indicating the name of the Element, e.g., ,.
The Elements can be named freely (as far as the syntax and encodign rules are respected).
It is possible to have nested Elements.
Elements can have attributes, e.g., .
XML is case sensitive, e.g., is different from .

+ Show What is a DTD?

DTD corresponds to Document Type Defnition.
A DTD file defines some conditions for an XML file; for instance, it describes in which sequence XML elements are expected and what attributes are allowed.
DTDs are useful to validate XML data.