xml – part iii. the element … this type of element either has the element content or the mixed...

XML – Part III

The <complexType> Element …This type of element either has the element

content or the mixed content (child element and data)

The attributes of the <complexType> element include:‘id’, which provides a unique id for the element

‘mixed’, a Boolean that indicates whether the element has a mixed content or not (the default value is false), and

‘name’, which gives a name to the element

complexType’s children elements The children elements of the

<complexType> element can be:

<simpleContent><complexContent><all><group><sequence>

simpleContent …The simpleContent allows the complexType element to

have leaf nodes of character data, without any child element

The content of a simpleContent element must either be: extension or restriction of an existing built in or derived datatypes

As an example for using extension, we can make a complexType element called RockName by extending the built in string datatype in the simpleContent element

The RockName element (next slide) can only have character data as its value

complexType by simpleContent by extension

<xs:element name="RockName"> <xs:complexType> <xs:simpleContent> <xs:extension base="xs:string"/> </xs:simpleContent> </xs:complexType></xs:element>

complextype by simpleContent by restrictionAs an example for using a restriction in the

simpleContent of a complexType, we can define the complexType called CelciusTemperature by restricting the xs:decimal number to have a minimum value of -273.15 oC

<xs:element name="CelciusTemperature"> <xs:complexType> <xs:simpleContent> <xs:restriction base="xs:decimal"/> <minInclusive value="-273.15"/> </xs:simpleContent> </xs:complexType></xs:element>

complexType with complexContentThe complexType element with complexContent can

be built by adding element content, or a combination of child elements and character data, i.e., mixed content

This is done by defining a list of elements and attributes

The following is an example of a complexType element called MineralInfo with an element content, using the <xs:sequence> which defines the order that the child element should appear

Note that in this example, there is no need to have the <xs:complexContent> element at all. We can just put the <xs:sequence> in the <xs:compleType>

complexType w/ element content <?xml version="1.0" encoding="UTF-8"?>

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:element name="MineralInfo"> <xs:complextype> < !-- <xs:complexContent> --> <xs:sequence> <xs:element name="name"/> <xs:element name="type"/> <xs:element name="composition"/> <xs:element name="hardness"/> <!-- other physical and chem. properties --> </xs:sequence> < !-- </xs:complexContent> --> </xs:complextype> </xs:element></xs:schema>

Mixed contentWe can now build a mineralogy element whose

type is MineralInfo.<xs:element name=”Mineralogy” type=”MineralInfo”/>

To build a mixed content <complexType> element we set the ‘mixed’ attribute of the <complexType> element to ‘true’

This allows us to add text nodes before, between, and after the child nodes

In the following, we define a Rock element that allows writing the description of the rock in text, anywhere in the document

Example of mixed content <xs:element name="Rock">

<xs:complexType mixed=”true”> <xs:sequence> < !-- assume MineralInfo is already declared --> <xs:element name="Mineralogy" type="MineralInfo"/> <xs:element name="type"/> </xs:sequence> </xs:complexType></xs:element>

<xs:sequence>The <xs:sequence> element provides a mandatory

order to the sequence of elements in a complex type.

For example, to force the dip to follow the strike of a planar structure, we can use the sequence element to do just that

<xs:element name="PlanarAttitude">

<xs:complexType> <xs:sequence> <xs:element name="Strike" type="xs:string"/> <xs:element name="Dip" type="xs:string"/> </xs:sequence> </xs:complexType></xs:element>

Let’s say that some geologists provide dip direction and dip amount, instead of strike and dip for a planar feature, and we want to give them this option to enter their data. We do it as follows:

<xs:element name="PlanarAttitude"> <xs:complexType>

<xs:group> <xs:sequence>

<! -- defines a group containing a choice of two sequences -- > <xs:group> <xs:choice> <xs:sequence> <xs:element name="Strike" type="xs:string"/> <xs:element name="Dip" type="xs:string"/> </xs:sequence> <xs:sequence> <xs:element name="DipDirection" type="xs:string"/> <xs:element name="DipAmount" type="xs:string"/> </xs:sequence> </xs:choice> </xs:group> </xs:sequence> </xs:group> </xs:complexType></xs:element>

XML instance documentBecause of the choice, we may have either

one of the following in an instance document:

<PlanarAttitude> <Strike> N30E </Strike> <Dip> 65SE </Dip></PlanarAttitude>

or

<PlanarAttitude> <DipDirection> S60E </DipDirection> <DipAmount> 65 </DipAmount></PlanarAttitude>

<xs:all>In contrast to the <xs:sequence> element, the

<xs:all> element does not put any restriction on the ordering of its sub-elements

However, the <xs:all> element must be at the top-level, and cannot contain, or be part of, a sequence or a choice

For example, we can define the ‘Structure’ element to have a set of elements in any order

This means that an instance document can have any of the Name, Type, and Attitude listed in any order

Example for <xs:all> <?xml version="1.0" encoding="UTF-8"?>

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"><xs:element name=“Structure"> <xs:complexType> <xs:all> <xs:element name="Name"/> <xs:element name="Type"/> <xs:element name="Attitude"/> </xs:all> </xs:complexType></xs:element></xs:schema>

AttributesIn W3C XSD schema, the attributes are declared with

the <xs:attribute> element, which has its own attributes

Local attributes can be declared within a certain element, as opposed to those that have a global scope, which are declared in the <schema> element, and that could be used by any element or attribute group

For example, we can define the local ‘TemperatureType’ attribute for the Temperature element, to indicate the type of the temperature system (Celcius, Farenheit, etc.)

This attribute can only be referenced by instances of the Temperature element

Local attribute

<?xml version="1.0" encoding="UTF-8"?><xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"><xs:element name="Temperature"> <xs:complexType> <xs:attribute name="TemperatureType"/> </xs:complexType></xs:element></xs:schema>

Attributes of the <xs:attribute>The attribute element has several attributes of its

own, and include name, type, default, fixed, id, ref, and use:

The ‘name’ attribute of the <attribute> element specifies the name for the attribute, which needs to be a valid XML name, e.g., <attribute name=”color” type=”xs:string”/>

Notice that the type for the attribute is given by the W3C XSD string datatype

We can have two attributes with the same name only if their type is different, and defined in different content (one for an element, and the other as an attribute)

The ‘type’ attribute specifies the simple built-in or derived (i.e., restriction of simple types) datatype for the attribute in the instance document

These datatypes include (there are many more): boolean, integer, decimal, float, date, time, and string.

Contrary to the elements, attributes cannot have complex types

The ‘default’ attribute of the <attribute> element assigns a preset value to the attribute if no value is given in the instance document

For example, we can define an attribute for kink bands to specify their straight limb and angular hinge as follows:

<xs:attribute name="style" default="straight limb, angular hinge"/>

Or, we can define the sample attribute with a default value of ‘rock’ as follows:

<xs:attribute name=”sample” default=”rock” type=”xs:string”/>

In this case, if not specified, the sample type will be assigned to ‘rock’. Note: there might be other sample types: water, soil, etc.

If we want the value of an attribute not to change, we use the ‘fixed’ attribute

For example, if we want the formula for quartz to always be SiO2, we can fix it as follows:

<xs:attribute name=”quartzFormula” fixed=”SiO2”/>

The id attribute specifies a unique identifier for the attribute

The id can then be referenced by other elements

Notice that an attribute can also be referenced by its name

The ref attributes allows referencing another attribute

For example, let’s say we have a complexType aquifer element, which has two types: confined and unconfined, each with its own set of attributes that are of type ref, which reference the porosity and permeability attributes

Notice that the references to the porosity and permeability attributes are global because they are declared in the schema element before the porosity and permeability are declared

<?xml version="1.0" encoding="UTF-8"?><xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:element name="Aquifer"> <xs:complexType> <xs:sequence> <xs:element name="ConfinedAquifer"> <xs:complexType mixed="true"> <xs:attribute ref="porosity"/> <xs:attribute ref="permeability"/> </xs:complexType> </xs:element> <xs:element name="UnConfinedAquifer"> <xs:complexType mixed="true"> <xs:attribute ref="porosity"/> <xs:attribute ref="permeability"/> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> </xs:element>

<!- - These attributes are global; defined in the schema - - > <xs:attribute name=“porosity" type="xs:string"/>

<xs:attribute name=“permeability" type="xs:string"/> </xs:schema>

The ‘use’ attribute specifies the usage of the <xs:attribute> with its own ‘optional’, ‘prohibited’, and ‘required’ attributes

The default value for the ‘use’ attribute, when none of these is defined, is ‘optional’

Contrary to the ‘required’ value, which specifies that the attribute must be present, the prohibited value indicates that the attributes should not be used at all

In addition to the ref attribute which allows referencing

and reuse of attributes, we can structure and reference a group of attributes by the <attributeGroup>

For example, we can structure information about folds in a group called FoldInfo, and then reference it with the name of the group in an element called Measurement

<?xml version="1.0" encoding="UTF-8"?><xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:attributeGroup name="FoldfInfo"> <xs:attribute name="hingeline" use="optional" type="xs:string"/> <xs:attribute name="axis" use="optional" type="xs:string"/> <xs:attribute name="axialPlane" type="xs:string"/> <xs:attribute name="limb1" use="required" type="xs:string"/> <xs:attribute name="limb2" use="required" type="xs:string"/> <xs:attribute name="limb3" use="optional" type="xs:string"/> <xs:attribute name="limb4" use="optional" type="xs:string"/> <xs:attribute name="axialTrace" type="xs:string"/> </xs:attributeGroup>

<xs:element name="Measurement">

<xs:complexType> <xs:sequence> <xs:element name="Fold"> <xs:complexType> <xs:attributeGroup ref="FoldfInfo"/> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> </xs:element></xs:schema>

EnumerationsEnumeration is a list of options that a user can select

from

For example, we can enumerate the exhaustive list of the types for minerals

We define an attribute called mineralType that has an enumeration of the mineral types

We then reference this attribute in the Mineral element

Notice that enumeration is a restriction of a simpleType

<?xml version="1.0" encoding="UTF-8"?><xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:attribute name="mineralType"> <xs:simpleType> <xs:restriction base="xs:string"> <xs:enumeration value="silicate"/> <xs:enumeration value="carbonte"/> <xs:enumeration value="oxide"/> <xs:enumeration value="hydroxide"/> <!-- other types of minerals --> </xs:restriction> </xs:simpleType> </xs:attribute> <xs:element name="Mineral"> <xs:complexType> <xs:attribute ref="mineralType"/> </xs:complexType> </xs:element></xs:schema>

Linking XSD schemas with instance documentsThe XML processor that manipulates an instance

documents uses a special namespace that carries information on identifying the location and type of the associated schema

The namespace URI for the instance document: http://www.w3.org/2001/XMLSchema-instance

This has the xsi prefix (Note: ‘i’ stands for ‘instance’).

The xsi namespace has four attributes:

xsi:type, xsi:nil, xsi:schemaLocation, and xsi:noNamespaceSchemaLocation

The xsi:type attribute assigns a type to the instance of specific elements in the document

The xsi:nil takes a Boolean value to indicate that an empty element is valid

The xsi:schemaLocation specifies the location of the XSD schema for the document, with two URIs: the targetNamespace for the schema the URI that points to the location of the schema

The xsi:noNamespaceSchemaLocation is used to locate schemas (similar to the xsi:schemaLocation) that have no namespace

For example, assume that we want to make an instance document from the following schema which has a Structure root element, with three elements of string type

<?xml version="1.0" encoding="UTF-8"?> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns="http://www.gsu.edu/xml/struc/structure"> <xs:element name=“Structure"> <xs:complexType> <xs:all> <xs:element name="Name" type="xs:string"/> <xs:element name="Type" type="xs:string"/> <xs:element name="Attitude" type="xs:string"/> </xs:all> </xs:complexType> </xs:element> </xs:schema>

A valid instance document based on the schema on the previous slide would look like the following:

<?xml version="1.0" encoding="UTF-8"?><Structure xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="file:/C:/Users/HAB/Desktop

/Structure.xsd"> <Name> Brevard </Name> <Type> Fault </Type> <Attitude> 045, 30NW </Attitude></Structure>

XSL TransformationWell-formed XML documents (i.e., those having a

valid XML syntax) can be viewed with an XML document reader, such as the Internet Explorer (by double-clicking the file in the Windows Explorer)

Although, very useful, rendering the XML document in a browser shows all the tags, and looks very cluttered.

Because XML concentrates on document structure and not presentation, it has the XSL (XML Stylesheet Language) standard which allows manipulation of the XML documents, and their controlled display on XML browsers or editors

XSL allows rendering the XML content into HTML, or tabular and other formats.

XSL is a more sophisticated XML styling language, using a scripting language XSLT), compared to CSS (Cascading Style Sheets) which was originally designed for HTML

Both have rules for say font size and color that are applied or associated to an XML document.