1969 Generalized Markup Language (GML)
1974 Standard Generalized Markup Language (SGML)
A detailed explanation of SGML by Erjavec
1996 Extensible Markup Language (XML)
for the World Wide Web
Necessity: An international standard to enable the sharing of machine-readable large-project documents in government, law, industry and military. These are documents that must remain readable for several decades...
The volume of information within our reach seems infinite, but the limitation of existing technology can make it difficult to access, a simple solution is necessary.
XML
XML is not itself a markup language
XML is a set of rules for building markup languages. Today, there are hundreds of XML-based languages.
Markup is information added to a document that enhances its meaning. It identifies the parts of a document and how they relate to each other. A markup language is a set of symbols that can be placed in the text of a document to demarcate and label the parts of that document. Note: As an open standard, XML is not tied to any company or married to any particular software.
XML
XML sticks to three primary strict rules
- all tags are lower case
- at the top of the page is a Document Type Definition (DTD) - that points to a set of rules, formally known as entity and element declarations, that define a markup language, or how the tags are arranged in a valid document.
- and all tags require both an opening and closing tag
XML
Example of XML
<?xml version="1.0" encoding="UTF-8"?>
<course>
<title>Emerging Media</title>
<discipline>Web Production</discipline>
<number>MEDP 285</number>
<description>
Students will work to construct web content
using a combination of technology.
</description>
<link>http://fm.hunter.cuny.edu/</link>
</course>
Take a look at WNYC's XML file: WNYC All Feeds
XML
Accessibility
One of the most promising applications of XML is as a format for application-to-application data exchange.
With its clear, simply syntax and unambiguous structure, XML is easy to read and parse by people and programs.
Any program that can read XML documents is an XML processor.
XML
Accessibility
XML processors include web browsers, XML editors (code editors i.e. Atom, Visual Studio...), data and archiving systems (iTunes)... XML processor reads XML documents and converts them into a representation for other programs to use. The XML processor parcels a stream of characters from files into meaningful chunks of information.
XML - RSS
Basic RSS Example
RSS Example Targeting iTunes (Apple example linked below)
Resources
- Feed Validator to check your XML file.
- Apple's instructions on creating a podcast
XML - RSS
There are tools available online to generate RSS feeds (one type of XML). Simply search "RSS Generator" or try the one below.
JSON
In the early 2000s JavaScript Object Notation (JSON) was introduced as an alternative to XML. It was standardized in 2013.
The JSON syntax requires less characters than XML and is therefore more lightweight - key for storing and transporting data.
JSON
The JSON format is syntactically identical to the code for creating JavaScript objects. JSON syntax rules:
- Data is in name/value pairs
- Data is separated by commas
- Curly braces hold objects
- Square brackets hold arrays
Here is an example link to a single iTunes track as described in JSON. JSON w3schools tutorial; JSON Apple News tutorial
XML
Example of XML
<?xml version="1.0" encoding="UTF-8"?>
<course>
<title>Emerging Media</title>
<discipline>Web Production</discipline>
<number>MEDP 285</number>
<description>
Students will work to construct web content
using a combination of technology.
</description>
<link>http://fm.hunter.cuny.edu/</link>
</course>
JSON
Example ofJSON
{
"course": {
"title": "Emerging Media",
"discipline": "Web Production",
"number": "MEDP 285",
"description": "Students will work to...",
"link": "http://fm.hunter.cuny.edu/"
}
}