XML 1h

XML: ContentsWhat is XML?What is Well Formed XML?What is Valid XML?Document Type DefinitionsScalable Vector Graphics (SVG)XML in 10 PointsSome Questions for You

What is XML?XML is a method of putting structured data in a file format. It is not a programming language; it doesnt DO anything

An XML document includes text and mark-up; just like HTML. XML permits new markup tags to be definedXML is rather more strict than HTML

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An Easy Example (SVG)

What is Well Formed XML?1.Taken as a whole, it matches the production labelled document.2.It meets all the well-formedness constraints given in the W3 specification.3.Each of the parsed entities which is referenced directly or indirectly within the document is well-formed.

I find this a bit vague

What is Well Formed XML?There are Elements, Tags and Character Data, eg:

Alan Turing

The whole example was a person Element. Alan Turing was Character Data was a tag

What is Well Formed XML?Elements MUST be closedTags may be opening or closing tags of elementsAlternatively, single tags may be closed by a slash, eg

Elements may also be empty

What is Well Formed XML?Tags have Names and Attributes (p was a name; font was an attribute)

XML is case sensitive, so the name BR is regarded as different to br

XML must be well nested: Horrors!!!

What is Well Formed XML?Names and attributes may contain:

AZ, az or the characters of ANY alphabet (eg: ...)Numbers 09Underscore_ Hyphen- Period.Thats it.

What is Well Formed XML?Tags must be closed.Elements may contain elements - nesting must "proper".Tags may contain attributes.Characters such as < and & must be "escaped" as < and & - they have a special significance in XML and may not appear in data unescaped

What is Well Formed XML?Must begin with the XML declarationMust have one unique root elementAll start tags must match end-tagsXML tags are case sensitiveAll elements must be closedAll elements must be properly nestedAll attribute values must be quotedXML entities must be used for special characters

What is Well Formed XML?Well-formedness is not the same as Validity (see later)

Amazingly strict rule:If a parser encounters a well-formedness violation while parsing a document, it MUST STOP (usually with a useful error message)

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What is Valid XML?If an XML document is well-formed we may ask if it is valid. A valid XML document is one that agrees with the additional rules set out in a DTD (document type definition). The DTD includes: ELEMENT: These dictate what kind of child nodes each element is permitted.ATTLIST: This indicates what kind of attributes are permitted.

Scalable Vector Graphics (SVG)(In bit-map graphics we specify the colour of each pixel in a grid). This isnt it.Instead, we describe objects to be rendered. Allows us to produce graphics (boxes, lines, curves, text) in a scalable format. Arbitrarily high resolution with constant file size. Similar to Flash (but Flash has binary format)Designed and controlled by W3C

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An Easy Example (SVG)

Scalable Vector Graphics (SVG)Good example of an XML application. Standard defined by www.w3.org W3C supply a DTD and a description of how each element should be interpretedAnyone can produce a processor for the languageAnyone can produce content.

Narrative and Record Documents XML documents normally fall into two categories:An XHTML description of a web page starts at the beginning of the document and works its way down to the endAn XML description of a spreadsheet simply describes the data (there isnt a beginning or an end)

Narrative and Record Documents

An XHTML web page is an example of a Narrative document

A spreadsheet in Microsoft Office Open XML (OOXML) is an example of a record document.

XML in 10 Points1. XML lets you put structured data in a text file 2. XML looks like HTML but isn't HTML 3. XML is text, but isn't meant to be read 4. XML is a family of technologies 5. XML is verbose, but that is not a problem

XML in 10 Points6. XML is new, but not that new 7. XML is license-free8. XML is platform-independent9. XML is well-supported 10. XML is a W3 standard11. For what it does, there are no competitors

Recap of UnitWhat is XML?What is Well Formed XML?What is Valid XML?Document Type DefinitionsScalable Vector Graphics (SVG)XML in 10 PointsSome Questions for You