1. New Perspectives on XML, 2nd Edition
TUTORIAL 4
WORKING WITH SCHEMAS
New Perspectives on XML, 2nd Edition
Tutorial 4

2. New Perspectives on XML, 2nd Edition
SCHEMAS
A schema is an XML document that defines the content and structure of one or more XML documents.
The XML document containing the content is called the instance document.
New Perspectives on XML, 2nd Edition
Tutorial 4

3. COMPARING SCHEMAS AND DTDS
This figure compares schemas and DTDs
New Perspectives on XML, 2nd Edition
Tutorial 4

4. New Perspectives on XML, 2nd Edition
SCHEMA VOCABULARIES
There is no single schema form. Several schema “vocabularies” have been developed in the XML language.
Support for a particular schema depends on the XML parser being used for validation.
New Perspectives on XML, 2nd Edition
Tutorial 4

5. This figure shows a few schema vocabularies
New Perspectives on XML, 2nd Edition
Tutorial 4

6. New Perspectives on XML, 2nd Edition
STARTING A SCHEMA FILE
A schema is always placed in a separate XML document that is referenced by the instance document.
New Perspectives on XML, 2nd Edition
Tutorial 4

7. New Perspectives on XML, 2nd Edition
Example Schema
<?xml version="1.0"?> < xs:schema xmlns:xs=" <xs:element name="note">   <xs:complexType>     <xs:sequence>       <xs:element name="to" type="xs:string"/>       <xs:element name="from" type="xs:string"/>       <xs:element name="heading" type="xs:string"/>       <xs:element name="body" type="xs:string"/>     </xs:sequence>   </xs:complexType> < /xs:element> < /xs:schema>
New Perspectives on XML, 2nd Edition
Tutorial 4

8. ELEMENTS AND ATTRIBUTES OF THE PATIENTS DOCUMENT
This figure shows the elements and attributes of the patients.xml document
See pages 147 and 148
New Perspectives on XML, 2nd Edition
Tutorial 4

9. New Perspectives on XML, 2nd Edition
SCHEMA TYPES
XML Schema recognize two categories of types:
Simple type contains only a single value
Value of an attribute
Or the textual content of an element
Complex type
Contains a structure
New Perspectives on XML, 2nd Edition
Tutorial 4

10. This figure shows types of elements
SCHEMA TYPES
This figure shows types of elements
New Perspectives on XML, 2nd Edition
Tutorial 4

11. New Perspectives on XML, 2nd Edition
SIMPLE TYPE ELEMENTS
Use the following syntax to declare a simple type element in XML Schema:
<element name=“name” type =“type”/>
name = the name of the element in the instance document
type = the data type of the element.
Example:
<xs:element name = “lastName” type = “xs:string” />
Unlike DTD, schema is
an XML language
New Perspectives on XML, 2nd Edition
Tutorial 4

12. UNDERSTANDING DATA TYPES
XML Schema supports two data types
A built-in data type is part of the XML Schema specifications and is available to all XML Schema authors.
A user-derived data type is created by the XML Schema author for specific data values in the instance document.
New Perspectives on XML, 2nd Edition
Tutorial 4

13. DECLARING AN ATTRIBUTE
An attribute is another example of a simple type. The syntax to define an attribute is
<xs:attribute name=“name” type="type” default=“default” fixed=“fixed” />
name = the name of the attribute
type = the data type,
default = the attribute’s default value
fixed = a fixed value for the attribute
For examle:
<xs:attribute name=“Gender” type=“xs:string” default=“female” />
By convention, use xs for namespace for XML Schma namespace
optional
New Perspectives on XML, 2nd Edition
Tutorial 4

14. ASSOCIATING ATTRIBUTES AND ELEMENTS
The basic structure for defining a complex type with XML Schema is
<xs:element name="name">
<xs:complexType>
declarations
</xs:complexType>
</xs:element>
name = the name of the element
declarations = schema commands specific to the type of complex element being defined.
New Perspectives on XML, 2nd Edition
Tutorial 4

15. ASSOCIATING ATTRIBUTES AND ELEMENTS
Four complex type elements that usually appear in an instance document are the following:
The element is an empty element and contains only attributes.
The element contains textual content and attributes but no child elements.
The element contains child elements but not attributes.
The element contains both child elements and attributes.
The following slides describe each of these
New Perspectives on XML, 2nd Edition
Tutorial 4

16. EMPTY ELEMENTS AND ATTRIBUTES
The code to declare the attributes of an empty element is
<xs:element name="name">
<xs:complexType>
attributes
</xs:complexType>
</xs:element>
attributes = the set of declarations that define the attributes associated with the element
New Perspectives on XML, 2nd Edition
Tutorial 4

17. EMPTY ELEMENTS AND ATTRIBUTES
For example:
<xs: element name=“subject”>
<xs:complexType>
<xs:attriubute name=“name” type=“xs:string” />
<xs:attriubute name=“age” type=“xs:string” />
</xs: complexType>
</xs:element>
describes the following empty element:
<subject name=“Cynthia Dibbs” age=“62” />
New Perspectives on XML, 2nd Edition
Tutorial 4

18. SIMPLE CONTENT AND ATTRIBUTES
If an element is not empty and contains textual content (but no child elements), the structure of the complex type element is slightly different.
<xs:element name="name">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="type">
attributes
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
New Perspectives on XML, 2nd Edition
Tutorial 4

19. SIMPLE CONTENT AND ATTRIBUTES
Indicates text but no child
For example:
<xs:element name=“performance”>
<xs:complexType>
<xs:simpleContent>
<xs:extension base=“xs:string”>
<xs:attribute name=“scale” type=“xs:string”/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
defines
<performance scale=“Karnofskyk”>0.81</performance>
Extended to include an attribute
New Perspectives on XML, 2nd Edition
Tutorial 4

20. SPECIFYING THE USE OF AN ATTRIBUTE
An attribute may or may not be required with a particular element. To indicate whether an attribute is required, you add the use attribute to the element declaration or reference. The use attribute has the following values:
required—The attribute must always appear with the element
optional—(default) The use of the attribute is optional with the element
prohibited—The attribute cannot be used with the element
For example, the previous attribute declaration is modified as:
<xs:attribute name=“scale” type=“xs:string” use=“required”/>
New Perspectives on XML, 2nd Edition
Tutorial 4

21. REFERENCING AN ELEMENT OR ATTRIBUTE
Rather than nesting the attribute declaration within the element, you can create a reference to it. The code to create a reference to an element or attribute declaration is
<xs:element ref="elemName" />
<xs:attribute ref="attName" />
where
elemName = the name used in an element declaration
attName = the name used in an attribute declaration
New Perspectives on XML, 2nd Edition
Tutorial 4

22. REFERENCING AN ELEMENT OR ATTRIBUTE
<xs:attribute name=“scale” type=“xs:string” /> <xs:element name=“performance”> <xs:complexType> <xs:simpleContent> <xs:extension base = “xs:string> <xs:attribute> ref=“scale” use=“required” /> </xs:extension> </xs:simpleContent> </xs:complexType> </xs:element>
New Perspectives on XML, 2nd Edition
Tutorial 4

23. WORKING WITH CHILD ELEMENTS
Another kind of complex type element contains child elements, but no attributes. To define these child elements, use the code structure
<xs:element name="name">
<xs:complexType>
<xs:compositor>
elements
</xs:compositor>
</xs:complexType>
</xs:element>
where
elements =the list of simple type element declarations for each child element
compositor = defines how the child elements are organized.
New Perspectives on XML, 2nd Edition
Tutorial 4

24. New Perspectives on XML, 2nd Edition
USING COMPOSITORS
XML Schema supports the following compositors:
sequence defines a specific order for the child elements
choice allows any one of the child elements to appear in the instance document
all allows any of the child elements to appear in any order in the instance document; however, they must appear either only once or not all.
New Perspectives on XML, 2nd Edition
Tutorial 4

25. New Perspectives on XML, 2nd Edition
USING COMPOSITORS
<element name=“address”>
<xs:complexType>
<xs:sequence>
<xs:element name = “street” type = “xs:string”/>
<xs:element name = “city” type = “xs:string”/>
<xs:element name = “state” type = “xs:string”/>
</xs:sequence>
</element>
Must be in sequence
New Perspectives on XML, 2nd Edition
Tutorial 4

26. USING COMPOSITORS
<element name=“Family”>
<xs:complexType>
<xs:all>
<xs:element name = “Father” type = “xs:string”/>
<xs:element name = “Mother” type = “xs:string”/>
</xs:all>
</element>
Family may contain Father and/or Mother in no particular order
New Perspectives on XML, 2nd Edition
Tutorial 4

27. SPECIFYING THE OCCURENCES OF AN ITEM
<xs:element name=“patient” type=“xs:string” minOccurs=“1” maxOccurs=“3”/>
New Perspectives on XML, 2nd Edition
Tutorial 4

28. WORKING WITH CHILD ELEMENTS AND ATTRIBUTES
The code for a complex type element that contains both attributes and child elements is
<xs:element name="name">
<xs:complexType>
<xs:compositor>
elements
</xs:compositor>
</xs:complexType>
attributes
</xs:element>
New Perspectives on XML, 2nd Edition
Tutorial 4

29. CHILD ELEMENTS AND ATTRIBUTES EXAMPLE
<xs:element name=“patient”>
<xs:complexType>
<xs:sequence>
<xs:element ref=“lastname”/>
<xs:element ref=“firstName”/>
</xs:sequence>
<xs:attribute ref=“patID use=“required”>
</xs:complexType>
<xs:element>
New Perspectives on XML, 2nd Edition
Tutorial 4

30. SPECIFYING MIXED CONTENT
<Summary>
Patient <Name>Cynthia Davis</Name> was enrolled in
the <Study>Tamoxifen Study</Study> on 8/15/2003.
</Summary>
can be declared in the schema file using the following complex type:
<element name="Summary">
<complexType mixed="true">
<sequence>
<element name="Name" type="string"/>
<element name="Study" type="string"/>
</sequence>
</complexType>
</element>
element contains both text and child elements
New Perspectives on XML, 2nd Edition
Tutorial 4

31. APPLYING A SCHEMA
To attach a schema to the document, you must do the following:
Declare a namespace for XML Schema in the instance document.
Indicate the location of the schema file.
Example:
xmlns:xsi=
xsi=SchemaLocation=“pschema.xsd”>
Commonly used for XML Schema instances
Schema instance namespace
New Perspectives on XML, 2nd Edition
Tutorial 4

32. APPLYING A SCHEMA Specifying a schema in an XML document
is treated only as a hint by validating parsers
ignored by some parsers
Not allowed to prevent improper financial documents from being fraudulently submitted
If there is no namespace for the contents of the instance document, add the following attribute to the root element:
xsi:noNamespaceSchemaLocation="schema"
Schema instance namespace
New Perspectives on XML, 2nd Edition
Tutorial 4

33. New Perspectives on XML, 2nd Edition
Pause and breath
New Perspectives on XML, 2nd Edition
Tutorial 4

34. UNDERSTANDING DATA TYPES
A primitive data type, also called a base type, is one of 19 fundamental data types not defined in terms of other types.
A derived data type is a collection of 25 data types that the XML Schema developers created based on the 19 primitive types.
New Perspectives on XML, 2nd Edition
Tutorial 4

35. UNDERSTANDING DATA TYPES
This figure shows the 44 built-in data types
Page XML 168
Premitive
types
Dates & times
Derived
Types
New Perspectives on XML, 2nd Edition
Tutorial 4

36. UNDERSTANDING DATA TYPES
This figure shows a partial description of XML string data types
Page XML 169
New Perspectives on XML, 2nd Edition
Tutorial 4

37. New Perspectives on XML, 2nd Edition
USING DATA TYPES
Examples:
<xs:attribute name=“patID” type=“xs:ID” />
<xs:attribute name=“onStudy” type=“xs:string” />
<xs:attribute name=“scale” type=“xs:string” />
New Perspectives on XML, 2nd Edition
Tutorial 4

38. UNDERSTANDING DATA TYPES
This figure shows a partial description of XML numeric data types
Page XML 170
New Perspectives on XML, 2nd Edition
Tutorial 4

39. UNDERSTANDING DATA TYPES
This figure shows a partial description of XML date and time data types
Page XML 171
New Perspectives on XML, 2nd Edition
Tutorial 4

40. DERIVING NEW DATA TYPES
Three components are involved in deriving new data types:
Value space: the set of values that correspond to the data type.
Lexical space: the set of textual representations of the value space.
Facets: the properties of the data type that distinguish one data type from another.
Text string length, range of allowable values,
New Perspectives on XML, 2nd Edition
Tutorial 4

41. New Perspectives on XML, 2nd Edition
USER DERIVED DATA
New data types fall into three categories:
List: a list of values where each list is derived from a base type.
Union: the combination of two or more data types.
Restriction: a limit placed on the facet of a base type.
New Perspectives on XML, 2nd Edition
Tutorial 4

42. New Perspectives on XML, 2nd Edition
LIST
List data type is a list of values separated by white space
To create a list data type:
<xs:simpleType name=wbcList”>
<xs:list itemType=xs:decimal” />
<xs:simpleType>
To use the data type:
<xs:element name=“wbc” type=“wbcList” />
<wbe> </wbc>
New Perspectives on XML, 2nd Edition
Tutorial 4

43. DERIVING A RESTRICTED DATA TYPE
The most common way to derive a new data type is to restrict the properties of a base type. XML Schema provides twelve constraining facets for this purpose.
New Perspectives on XML, 2nd Edition
Tutorial 4

44. This figure shows the 12 constraining facets
New Perspectives on XML, 2nd Edition
Tutorial 4

45. CONSTRAINING FACETS EXAMPLE
<xs:simpleType name=“ageType”> <xs:restriction base=“xs:integer”> <xs:minInclusive value = “21” /> </xs:restriction> </xs:simpleType>
Constrains the data type to be greater than or equal to the value
New Perspectives on XML, 2nd Edition
Tutorial 4

46. New Perspectives on XML, 2nd Edition
The Patterns Facet
A pattern can be created with a formatted text string called a regular expression or regex.
To apply a regular expression in a data type, you use the code
<xs:simpleType name="name">
<xs:restriction base="type">
<xs:pattern value="regex"/>
</xs:restriction>
</xs:simpleType>
Where regex is a regular expression pattern.
New Perspectives on XML, 2nd Edition
Tutorial 4

47. New Perspectives on XML, 2nd Edition
Regular Expressions
Figure 4-30 page 184 shows character types, for example
\d a digit from 0 to 9
\D non digit character
Etc.
Figure 4-31 page 185 shows character sets, for example
[chars] Match any character in the chars list
[a-z] Match any lower case letter
[0-9] matach any digit form 0-9
New Perspectives on XML, 2nd Edition
Tutorial 4

48. This figure shows pattern quantifiers
New Perspectives on XML, 2nd Edition
Tutorial 4

49. EXAMPLE REGULAR EXPRESSIONS
<xs:pattern value=“\d{3}” />
<xs:pattern value=“[A-Z]*” />
<xs:pattern value=“[A-Z]{0,10}*” /}
<xs:ximpleType name=“mrType”>
<sx:restrictiion base=“xs:ID”>
<xs:pattern value=“MR\d{3}-\d{3}-d2{2}” />
</xs:restriction>
<xs:simpleType>
New Perspectives on XML, 2nd Edition
Tutorial 4

50. WORKING WITH NAMED TYPES
Schema authors can create customized complex types.
Advantage: reuse the complex structure in several places in the document.
For example:
<xs:element name=“fullName">
<xs:complexType>
<xs:sequence>
<xs:element name="firstName" type="xs:string"/>
<xs:element name="lastName" type="xs:string" />
</xs:sequence>
</xs:complexType>
</xs:element>
Use
<xs:element name=“client” type=“fullName”/>
<xs:element name=“salesperson” type=“fullName”/>
New Perspectives on XML, 2nd Edition
Tutorial 4

51. New Perspectives on XML, 2nd Edition
NAMED MODEL GROUPS
A named model group is a collection, or group, of elements.
Syntax
<xs:group name="name">
elements
</xs:group>
Where name is the name of the model group, and elements is a collection of element declarations
New Perspectives on XML, 2nd Edition
Tutorial 4

52. NAMED MODEL GROUPS EXAMPLE
Definition
<xs:group name=“fullName”>
<xs:sequence>
<xs:element name="firstName" type="xs:string"/>
<xs:element name="lastName" type="xs:string" />
</xs:sequence>
</xs:group>
Use
<xs:element name=“client">
<xs:complexType>
<xs:group ref=“fullName”/>>
</xs:complexType>
</xs:element>
New Perspectives on XML, 2nd Edition
Tutorial 4

53. WORKING WITH NAMED ATTRIBUTE GROUPS
Attributes can be grouped into collections called named attribute groups.
This is particularly useful for attributes that you want to use with several different elements in a schema. The syntax for a named attribute group is
<xs:attributeGroup name="name">
attributes
</xs:attributeGroup>
Where name is the name of the attribute group and attributes is a collection of attributes assigned to the group.
New Perspectives on XML, 2nd Edition
Tutorial 4

54. WORKING WITH NAMED ATTRIBUTE GROUPS
Example:
<xs:attributeGroup name=“DRInfo”>
<xs:attribute name=“DRID” type=“xs:string” use=“required” />
<xs:attribute name=“dept” type=“xs:string” use=“required” />
<xs:attributeGroup>
<xs:element name=“doctor” type=“deptData”/>
<xs:complexType name = “deptData”>
<xs:simplecontent>
<xs: extension base = “string”>
<xs:attributegroup ref=“DRIinfo”/>
</xs:extenson>
</xs:simplecontent>
</xs:complexType>
<doctor DRID=“DR251” dept=“Pediatrics”>
curt Hurley
<doctor>
New Perspectives on XML, 2nd Edition
Tutorial 4

55. New Perspectives on XML, 2nd Edition
SCOPE
An item has global scope = it is a child of a root schema element
Can be referenced and reused anywhere in the schema
An item has local scope = it is nested within another element
Can be referenced and reused only within the item in which it is declared
New Perspectives on XML, 2nd Edition
Tutorial 4

56. New Perspectives on XML, 2nd Edition
STRUCTURING A SCHEMA
Schemas can be structured in several ways:
Flat catalog (also called salami slice)
All declarations are made globally
Russian doll
Has only one global element
Everything else is nested inside of that element
Venetian Blind Design
Similar to flat catalog, except
Creates types and references within a single global element
New Perspectives on XML, 2nd Edition
Tutorial 4

57. New Perspectives on XML, 2nd Edition
STRUCTURING A SCHEMA
One schema design is a Flat Catalog Design.
Sometimes called salami slice design
In this design, all element declarations are made globally.
The structure of the instance document is created by referencing the global element declarations.
New Perspectives on XML, 2nd Edition
Tutorial 4

58. This figure shows a Flat Catalog design
Figure 4-36 page 192
This figure shows a Flat Catalog design
New Perspectives on XML, 2nd Edition
Tutorial 4

59. New Perspectives on XML, 2nd Edition
STRUCTURING A SCHEMA
Schemas can be structured in a number of ways. One structure is called a Russian Doll design. This design involves sets of nested declarations.
While this design makes it easy to associate the schema with the instance document, it can be confusing and difficult to maintain.
New Perspectives on XML, 2nd Edition
Tutorial 4

60. This figure shows a Russian Doll design
Figure 4-37 page 193
This figure shows a Russian Doll design
New Perspectives on XML, 2nd Edition
Tutorial 4

61. New Perspectives on XML, 2nd Edition
VENETIAN BLIND DESIGN
A Venetian blind design
Compromise between flat catalogs and Russian dolls
Element and attribute groups and named types are declared globally (and can be reused throughout the schema)
Elements and attributes for the instance document are local and nested
New Perspectives on XML, 2nd Edition
Tutorial 4

62. New Perspectives on XML, 2nd Edition
VENETIAN BLIND DESIGN
Figure 4-38 page 194
New Perspectives on XML, 2nd Edition
Tutorial 4

63. COMPARING SCHEMA DESIGNS
Figure 4-39 page 195
This figure compares the three schema designs
New Perspectives on XML, 2nd Edition
Tutorial 4

64. PLACING A SCHEMA IN A NAMESPACE: TARGETING A NAMESPACE
To associate a schema with a namespace
declare the namespace
prefix:xmlns="uri"
make that namespace the target of the schema.
targetNamespace="uri"
Where
prefix = prefix of the XML Schema namespace
uri = URI of the target namespace
New Perspectives on XML, 2nd Edition
Tutorial 4

65. PLACING A SCHEMA IN A NAMESPACE: TARGETING A NAMESPACE
Example (Figure 4-40):
<xs:schema xmlns:xs=
xmlns=“
targetNamespace=“
<xs: element name=“patients”>
<xs:complexType>
<xs:sequence>
<xs:element name=“patient” type=“pType”
Minoccurs = “1” maxoccurs=“unbounded” />
</xs:sequence>
</xs:complexType>
</xs:element> …
Declare the namespace
Make the new namespace the target of the schema
New Perspectives on XML, 2nd Edition
Tutorial 4

66. APPLYING A SCHEMA TO A DOCUMENT WITH A NAMESPACE
To apply a schema to a document with a namespace, add the following attributes to the instance document’s root element:
xmlns:xsi="
xsi:schemaLocation="uri schema"
Where uri is the URI of the namespace and schema is the location and name of the schema file.
All global elements and attributes from the schema must be qualified in the instance document.
New Perspectives on XML, 2nd Edition
Tutorial 4

67. APPLYING A SCHEMA TO A DOCUMENT WITH A NAMESPACE
Example:
<patients xmlns:xsi=
xmlns=“
xsi:schemaLocation= patvb.xsd>
<patient patID = “MR ” … ….
</patient>
New Perspectives on XML, 2nd Edition
Tutorial 4

68. INCLUDING AND IMPORTING SCHEMAS
To include a schema from the same namespace, add the following element as a child of the schema element:
<xs:include schemaLocation="schema" />
Where schema is the name and location of the schema file.
To import a schema from a different namespace, use the syntax
<xs:import namespace="uri" schemaLocation="schema" />
Where uri is the URI of the imported schema’s namespace and schema is the name and location of the schema file.
New Perspectives on XML, 2nd Edition
Tutorial 4

69. REFERENCING OBJECTS FROM OTHER SCHEMAS
Once a schema is imported, any objects it contains with global scope can be referenced
To reference an object from an imported schema, you must declare the namespace of the imported schema in the schema element
You can then reference the object using the ref attribute or the type attribute for customized simple and complex types
New Perspectives on XML, 2nd Edition
Tutorial 4

70. Assignment: Tutorial 4 Case Problem 1
Perform the tasks listed on pages 212 and 213
Create a CSS for the resulting jw.xml
Post your work, including the CSS on your web site.
End an with the subject: Tutorial 4 Case Problem 1 by <your name> to by Wednesday 11:50 May 1
New Perspectives on XML, 2nd Edition
Tutorial 4