Three Key Questions What is XML? What Problems does it solve? Where and how is it used?
What XML IS eXtensible A set of rules for creating and implementing markup languages that describe the structure of various kinds of documents and data Unicode text documents A cross platform, long term data format
What XML Is Not A programming language A network transport protocol (such as http or TCP/IP) A database A replacement of HTML The cure to all evils
What Problems Does it Solve It provides a standardized method of communicating data between systems, browsers and applications Provides the flexibility to describe and structure different kinds of data It separates data description from data display It provides a humanly readable format for document persistence
Where it is Used The short answer is everywhere Ebusiness Browsers (cdf) Wireless (wml) Math (Mathml), chemistry, biology Software description (OSD) Multimedia (SML) Graphics (SVG).Net
How it is Used Document transference Data processing and persistence Application messaging
Data Persistence XML provides a data format that is humanly readable if necessary Even if the originating program is lost or unavailable, it is relatively easy to write a program to parse and access the data from an XML file
A Brief History SGML ISO standard in 1986 HTML (an SGML application 1990) 1996 work on a “lite” version of SGML 1998 XML 1.0 a W3C recommendation Since then several XML “applications” : XSLT, XPATH, XLINK, XML Schema, etc.
W3C.org The World Wide Web Consortium http://www.w3c.org Levels of specification Working drafts Candidate Recommendations Proposed Recommendations Recommendations
W3C Goals for XML XML shall be straightforwardly usable over the Internet XML shall support a variety of applications XML shall be compatible with SGML It shall be easy to write programs that process XML
Goals Continued The number of optional features in XML is to be kept to a minimum, ideally zero XML documents should be humanly legible and reasonably clear XML design should be prepared quickly
Goals Continued The design of XML should be formal and concise Terseness in XML markup is of minimal importance XML documents shall be easy to create
XML Compared to HTML HTML Pre-established set of elements Mixes display with structure Loose and forgiving syntax Ascii Case insensitive XML Extensible (open) set of elements Separates display from structure Strict syntactical structure Unicode Case sensitive
XML 1.1 A new recommendation for the XML core standard was issued in February 2004. Because of changes in Unicode, XML names were changed so that everything that is not forbidden is allowed (was only what was specified was allowed)
XML 1.1 continued New characters added for compatibility with IBM mainframes, and Unicode. Not major changes, but does change the definition of “well-formed” so the new standard was developed.