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XML Extensible Markup Language
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Today: Imagine Cup –Wednesday, February 2nd from 6-8 pm in Lally Hall, Room 104, we will have a representative on campus for the Imagine Cup Program. Pizza and soda will be provided. Homework #1 XML In class: define your class schedule in XML (groups ~10) Tuesday: XSLT (reformatting XML)
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Standards Help or hinder innovation? Think about it
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Standards http://www.w3.org/ –HTML, CSS, XML, XPATH, SVG, Services, Semantic Web http://www.iana.org/ –URNs, DNS, IP Addresses http://www.ietf.org/ –HTTP, TCP/IP http://www.ieee.org/ –Ethernet, 802.1-, MAC addresses
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Standards NTSC –1936, industry recommendation –1941, B&W standard –1950, color standard –2009, FCC required shutdown of NTSC broadcast
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Standards Standards in Physical Infrastructure –European vs. US cell phone technology adoption rates (one euro standard v. 3 in the US) –Gas Stations & alternate fuels for personal transportation
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Standards Help or hinder innovation? Ok, lets have a discussion
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XML Organize Data –Consistent Syntax –Semantic Free
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Stuff we do with XML machine to machine transfer of models & data data storage (best for storing data in a tree format) sending data from the application to the presentation layer
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KML / AJAX Example Google maps consumes KML Outputs JS / XHTML / CSS Structured data can be reused.
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An Example XML Doc
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Some Common XML types Atom –Which is really cool because it can hold other formats within it RSS Itunes Library KML XHTML…
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XHTML A specific flavor of XML Defined by a DTD (Document Type Definition) –http://www.w3.org/TR/xhtml1/DTD/xhtml1- strict.dtd
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XML documents must be: Well-formed –Adhere to XML syntax rules Valid –Adhere to the rules in the specified DTD
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Root / Parents Elements must have a parent Documents must have one document root is the only top level element. It is the document root
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XML Syntax Rules Elements must have a closing tag: –... – Self closing tags
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Proper Nesting of Elements: blah blah
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Element Naming Rules Elements are lowercase only Elements must not start with “xml” Element names should not contain “-” or “:”
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Attributes Elements describe data Attributes describe elements Attributes must be in quotes Examples
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Namespaces Used to prevent element or attribute name or ‘meaning’ collisions Example Namespace collision Two namespaces namespace nameelement name
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Namespaces Pointing to a namespace xmlns attribute In –an element –global definition
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Namespaces In an element (applies to all of its children)
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Namespaces Global <html xmlns:h=“http://www.w3.org/1999/xhtml” xmlns:m="http://www.w3.org/1998/Math/MathML" >.. Some text
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Namespaces + Standards Decisions are expensive Use a preexisting format (no limit to number of namespaces on a page) http://www.dublincore.org/documents/dc- xml-guidelines/http://www.dublincore.org/documents/dc- xml-guidelines/
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DTD Document Type Definition Internal or external file describing list of elements, attributes and their relationships. Machine readable
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DTD Building Blocks Elements (describe data) Attributes (describe elements) PCDATA (the stuff between tags that gets parsed) CDATA - (data between tags that contains other data that you do not want parsed) Entities - (special items, such as & )
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DTD Elements Defining an element element name type
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DTD Elements Defining an empty element (no closing tag) Defining an element with children
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DTD Attributes Setting a default setting the default colspan value to 1 in a element
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DTD Attributes required attribute & implied attribute XML author must include a value for page to validate author does not have to include attribute/value and we aren't setting a default either
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DTD & Standards Load: http://www.w3.org/TR/xhtml1/DTD/xhtml1- transitional.dtd http://www.w3.org/TR/xhtml1/DTD/xhtml1- transitional.dtd Look at line 273 What are the first children elements allowed inside
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DTD & Standards http://validator.w3.org/ Validator compares rules in the DTD with the XML implemented.
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DTD Entities Exist in XML like this & + name + ; lt, jt, amp, apos, quot are supported by defualt DTD author can specify custom entities to operate as replacement variables –Example: &myname; –(replacement defined in the DTD)
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XHTML Entities http://www.w3schools.com/tags/ref_entitie s.asphttp://www.w3schools.com/tags/ref_entitie s.asp 5 ‘Reserved Characters’ must not be part of your page content … use HTML entities instead
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Entities JS or XSLT –Watch less than / greater than Input you don’t control –Watch everything!! Wrap data in CDATA
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Entities Wrap data in CDATA (will not be parsed)
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Entities hi ]]> Would display as hi
![Entities hi ]]> Would display as hi](http://images.slideplayer.com/17/5336052/slides/slide_39.jpg "Entities hi ]]> Would display as hi")
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Entities <?PHP $good = htmlentities ($bad); ?>
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