Quiz 2 Review
XML

• XML = Extensible Markup Language
• Language for describing data in a simple, straight forward format
• Saved as text file; anything that reads ASCII text file can read XML
• Allows documents and data to be read on many different platforms
• Can save information from many applications including MS Word,
Excel, Powerpoint, or CorelDraw as well as custom programs
• XML is not a database
• Is Markup language, not a programming language
• Does not do anything
• Only stores information in defined format
• Can provide data to instruct or guide the logic of a program
• XML specification http://www.xml.com/axml/testaxml.htm
• Other links on class website

• Basic unit of XML Data “element”
• Stored as “text string” and “marked-up” with surrounding tags in human readable format
• Never binary data in XML file
• Markup tags describe document’s structure
• Tag names describe data element purpose (i.e., date, name, person etc.)
• Elements associated with other elements in hierarchical structure
• Meta-Markup language that can have any number of tags unlike HTML that has fixed number of tags
• “Extensible” because users can define tags for elements as they need them
• Customizable and usable in many different domains
(i.e., web sites, data interchange, vector graphics, real estate etc.)
• “Grammar” regulates naming and placement of tags in documents
• “Well-formed” XML documents follows proper grammar

• XML “Application”
• Not executable programs in usual sense of “application”
• Set of agreed-upon “tags” used by organization or group of individuals to enhance interoperability between users
• XML being “Applied” in particular domain
• Real estate agency uses program that saves data to XML files, and posts information to website
• XML Application restricts data elements to those relevant to domain
• Might include “house”, “address”, “bedrooms”, “eat-in-kitchen” etc.
• Program will open and save XML files with only those agreed-upon tags
• Markups for particular XML Application defined in “document type definition” or DTD
• Lists all legal Markups for that domain
• Specifies where and how Markups can be used in a document
• Document might contain DTD itself or pointer to centrally located DTD

• Software packages use an XML “parser” to access XML documents
• “system.xml” namespace in Visual Studio C# environment provides tools for saving and extracting information in XML documents
• Information retrieved from XML document divided into “elements” and
“attributes” and passed to calling program piece by piece
• Parser reports errors when violation of XML rules detected or when document “instance” of XML Application does not match with DTD
• Documents that match DTD are valid; those that don’t are invalid
• Validity errors are not necessarily fatal and an application can continue to parse the XML file if desired
• XML documents that are not “well-formed” produce fatal errors
• Applications that might use XML parsers include...
• Web browsers, word processors, database servers, drawing programs, spreadsheets etc.

• Documents “Marked-up” with “start” and “end” tags
• Start tags begin with a “less-than” sign “<” followed by the element name and end with a “greater-than” sign “>”
<ElementName>
• End tags begin with a “less-than” sign and a forward slash “</” followed by the element name and end with a “greater-than” sign “>”
</ElementName>
• Everything between the start tag and end tag mark an element’s content
• The following simple XML document provides for a single element of type “person” with content “Alan Turing”
<person>
Alan Turing
</person> start tag element content end tag

(cont’d)
• Elements can have “attributes”
• “name-value” pairs defined within the start tag of an element
• Name is separated from value with equal sign
• In the following example, “born” and “died” are attributes of the element “person”
<person born = “1912/06/23” died=“1954/06/07” >
Alan Turing
</person>
• When do you use “attributes” vs “elements” to hold data?
• Depends on the use of the information and personal preference
• Some believe attributes should be metadata about element information
• Others say its too difficult to what is data or metadata
• No steadfast rules

(cont’d)
• XML documents are hierarchical trees with parent and child elements
• All elements have exactly one parent except the root element that has no parent
• Child element must be completely enclosed within a parent element start and end tags
<person>
<name> root element (aka document element) child of “person”; parent of “firstname” and “lastname”
<firstname> Alan </firstname>
<lastname> Turing </lastname> child of “name” child of “name”
</name>
<profession> computer scientist </profession> child of “person”
<profession> mathematician </profession>
<profession> cryptographer </profession> child of “person” child of “person”
</person>

(cont’d)
• Tree diagram of previous example person name profession profession profession firstname lastname
Alan Turing computer scientist mathematician cryptographer
Element
Element Content

(cont’d)
• Elements can have both character data and child elements in
“Mixed Content” elements
• Character Only: <person>Alan Turing</person>
• Child Elements Only: <name> <firstname>Alan</firstname>
<lastname>Turing</lastname>
</name>
• Mixed Content: <sentence>My name is <name>Tony</name> and I live in
<city>Ossining</city>.</sentence>
• XML is case sensitive
• <person> != <Person> != <PERSON>
• Must close element with same name as it was opened with
• <person> </person> OK
• <person> </PERSON> not OK
• Empty elements
• Line Break:
• Horizontal Rule:
<br/>
<hr/>

• Rules for element and attribute names are the same
• May contain ...
• Standard English Alpha-numeric: A-Z, a-z, 0-9
• Non-English numbers and ideograms: ö, ç, ψ etc.
• Punctuation characters: Underscore, Hyphen and Period
• May not contain ...
• Punctuation characters: Quotation marks, apostrophes, dollar signs, carets, percent symbols and semicolons
• Colon is allowed but reserved for use in namespaces
• White space of any kind such as space character, carriage return, line feed or non-breaking space
• Can start with ...
• Letters, ideograms or underscore
• Not a number, hyphen or a period
• There is no limit to name length

• “Entity References” are escape sequences to represent reserved characters within element content
• Less-than sign “<” is always interpreted as the beginning of a tag
• Use escape sequence &lt; to represent character within element content
• Five predefined Entity References in XML include ...
• Less-Than sign:
• Ampersand:
&lt;
&amp;
•
• Greater-Than sign:
Double Quotation:
&gt;
&quot;
• Single Quotation or Apostrophe: &apos;
• Only the &lt; (<) and &amp; (&) must be used instead of literal characters
• &quot; and &apos; can be used when literal apostrophe or double quote might be mistaken for the ending of an attribute value

• XML documents should begin with an XML Declaration, but is optional
• If document contains declaration, it must be first line in file
• Includes name, version, encoding and standalone attributes
<?xml version=“1.0” encoding=“US-ASCII” standalone=“yes”>
• Version attribute
• Always “1.0” as this is the most recent version
• Encoding attribute
• Provide name of encoding such as UTF-8 (8-bit Unicode Transformation
Format), ASCII, ISO-8859_1 etc
• Attribute is optional with UTF-8 as default
• Standalone attribute
• Refers to DTD location
• If value is “yes”: Internal or no DTD
• If value is “no”: external DTD is used
• Optional attribute with default value of “no”

<tiObjectList>
<Shape GeoType="FinalProject.tiPoint" Geometry="POINT (95 23)" ObjLineColor="Red" ObjLineThickness="1" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiPoint" Geometry="POINT (97 56)" ObjLineColor="Red" ObjLineThickness="2" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiPoint" Geometry="POINT (96 97)" ObjLineColor="Yellow" ObjLineThickness="3" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiPoint" Geometry="POINT (92 140)" ObjLineColor="Yellow" ObjLineThickness="4" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiPoint" Geometry="POINT (89 186)" ObjLineColor="Cyan" ObjLineThickness="5" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiPoint" Geometry="POINT (89 227)" ObjLineColor="Magenta" ObjLineThickness="6" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiPoint" Geometry="POINT (90 274)" ObjLineColor="Green" ObjLineThickness="7" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiPoint" Geometry="POINT (90 322)" ObjLineColor="Green" ObjLineThickness="8" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiPoint" Geometry="POINT (93 365)" ObjLineColor="Blue" ObjLineThickness="9" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiPoint" Geometry="POINT (97 405)" ObjLineColor="Black" ObjLineThickness="10" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiLineString" Geometry="LINESTRING (148 33, 196 132, 255 29, 319 133, 357 30)" ObjLineColor="Green" ObjLineThickness="8" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiPolygon" Geometry="POLYGON ((180 287, 183 390, 399 401, 387 277, 276 220, 180 287))" ObjLineColor="Cyan" ObjLineThickness="4" ObjFillColor="Black" ObjSelected="False" />
</tiObjectList>

<tiObjectList>
<Shape GeoType="FinalProject.tiPoint" Geometry="POINT (95 23)" ObjLineColor="Red" ObjLineThickness="1" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiPoint" Geometry="POINT (97 56)" ObjLineColor="Red" ObjLineThickness="2" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiPoint" Geometry="POINT (96 97)" ObjLineColor="Yellow" ObjLineThickness="3" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiPoint" Geometry="POINT (92 140)" ObjLineColor="Yellow" ObjLineThickness="4" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiPoint" Geometry="POINT (89 186)" ObjLineColor="Cyan" ObjLineThickness="5" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiPoint" Geometry="POINT (89 227)" ObjLineColor="Magenta" ObjLineThickness="6" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiPoint" Geometry="POINT (90 274)" ObjLineColor="Green" ObjLineThickness="7" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiPoint" Geometry="POINT (90 322)" ObjLineColor="Green" ObjLineThickness="8" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiPoint" Geometry="POINT (93 365)" ObjLineColor="Blue" ObjLineThickness="9" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiPoint" Geometry="POINT (97 405)" ObjLineColor="Black" ObjLineThickness="10" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiLineString" Geometry="LINESTRING (148 33, 196 132, 255 29, 319 133, 357 30)" ObjLineColor="Green" ObjLineThickness="8" ObjFillColor="" ObjSelected="False" />
<Shape GeoType="FinalProject.tiPolygon" Geometry="POLYGON ((180 287, 183 390, 399 401, 387 277, 276 220, 180 287))" ObjLineColor="Cyan" ObjLineThickness="4" ObjFillColor="Black" ObjSelected="False" />
</tiObjectList> using System.Xml; // Required for Xml documents private void saveToolStripMenuItem_Click( object sender, EventArgs e)
{
SaveFileDialog saveFileDialog1 = new SaveFileDialog (); // Create a save file dialog
XmlDocument xmlDoc = new XmlDocument (); if (saveFileDialog1.ShowDialog() == DialogResult .OK)
// Create an empty XML document
// Show the dialog. If OK is clicked,
// save the features to the selected file.
{
XmlElement elt = xmlDoc.CreateElement( "tiObjectList" ); foreach ( tiGeometry g in _tiGISObjectList._tiObjList)
// First, create a top-level element
// Then go through each feature and create
// a corresponding child element
{
XmlElement childElt = xmlDoc.CreateElement( "Shape" ); // Shape will be the name of each element; childElt.SetAttribute( "GeoType" , g.GetType().ToString()); childElt.SetAttribute( "Geometry" , g.tiObject.ToText() ); childElt.SetAttribute( "ObjLineColor" , g.tiObjLineColor); // class, type, and geometry will be the attributes.
childElt.SetAttribute( "ObjLineThickness" , g.tiObjLineThickness.ToString()); childElt.SetAttribute( "ObjFillColor" , g.tiObjFillColor); childElt.SetAttribute( "ObjSelected" , g.tiObjSelected.ToString()); elt.AppendChild(childElt); // Append the new element as a child element of the top-level element
} xmlDoc.AppendChild(elt); xmlDoc.Save(saveFileDialog1.FileName);
} saveFileDialog1.Dispose();
// Append the top-level element to the document
// Write out the XML to a file.
// Dispose of the save dialog object
}

private void openToolStripMenuItem_Click( object sender, EventArgs e)
{
OpenFileDialog openFileDialog1 = new OpenFileDialog ();
XmlDocument xmlDoc = new XmlDocument ();
// Create a open file dialog
// Create an empty XML document if (openFileDialog1.ShowDialog() == DialogResult .OK) // Show the dialog. If OK is clicked,
// save the features to the selected file.
{ xmlDoc.Load(openFileDialog1.FileName);
XmlElement elt = xmlDoc.DocumentElement;
_tiGISObjectList._tiObjList.Clear(); foreach ( XmlElement childElt in elt.ChildNodes)
// Load the Xml document from the given file.
// get top-level element
// clear out current object list
// go through XML child elements & add
// a corresponding geometry
{
String tempGeoType = childElt.GetAttribute( "GeoType" );
String tempGeo = childElt.GetAttribute( "Geometry" );
String tempObjCol = childElt.GetAttribute( "ObjLineColor" );
String tempObjLineThickness = childElt.GetAttribute( "ObjLineThickness" );
String tempObjFillCol = childElt.GetAttribute( "ObjFillColor" );
String tempSelected = childElt.GetAttribute( "ObjSelected" ); switch (tempGeoType)
{ case "FinalProject.tiPoint" :
{
_tiGISObjectList._tiObjList.Add( new tiPoint (tempObjCol, Convert .ToInt16(tempObjLineThickness),tempGeo));
_tiGISObjectList._tiObjList[_tiGISObjectList._tiObjList.Count - 1].tiObjSelected = Convert .ToBoolean(tempSelected); break ;
} case "FinalProject.tiLineString" :
{
_tiGISObjectList._tiObjList.Add( new tiLineString (tempObjCol, Convert .ToInt16(tempObjLineThickness), tempGeo));
_tiGISObjectList._tiObjList[_tiGISObjectList._tiObjList.Count - 1].tiObjSelected = Convert .ToBoolean(tempSelected); break ;
} case "FinalProject.tiPolygon" :
{
_tiGISObjectList._tiObjList.Add( new tiPolygon
(tempObjCol, tempObjFillCol, Convert .ToInt16(tempObjLineThickness), tempGeo));
_tiGISObjectList._tiObjList[_tiGISObjectList._tiObjList.Count - 1].tiObjSelected =
Convert .ToBoolean(tempSelected); break ;
}
}
}
} openFileDialog1.Dispose(); tiPictureBox.Refresh();
// Dispose of the open dialog object
//redraw scene
}