New Perspectives on XML, 2nd Edition

1

TUTORIAL 4

WORKING WITH SCHEMAS
2
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.

3
COMPARING SCHEMAS AND DTDS

• This figure compares schemas and DTDs

4
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.

5
SCHEMA VOCABULARIES

• This figure shows a few schema vocabularies

6
STARTING A SCHEMA FILE

• A schema is always placed in a separate XML
  document that is referenced by the instance
  document.

7
Example Schema

• lt?xml version"1.0"?gtlt xsschema
  xmlnsxs"http//www.w3.org/2001/XMLSchema"gtltxs
  element name"note"gt  ltxscomplexTypegt   
  ltxssequencegt      ltxselement name"to"
  type"xsstring"/gt      ltxselement name"from"
  type"xsstring"/gt      ltxselement
  name"heading" type"xsstring"/gt     
  ltxselement name"body" type"xsstring"/gt   
  lt/xssequencegt  lt/xscomplexTypegtlt
  /xselementgtlt /xsschemagt

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
9
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

10
SCHEMA TYPES

• This figure shows types of elements

11
SIMPLE TYPE ELEMENTS

• Use the following syntax to declare a simple type
  element in XML Schema
• ltelement namename type type/gt
• name the name of the element in the instance
  document
• type the data type of the element.
• Example
• ltxselement name lastName type xsstring
  /gt

Unlike DTD, schema is an XML language
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.

13
DECLARING AN ATTRIBUTE

• An attribute is another example of a simple type.
  The syntax to define an attribute is
• ltxsattribute namename type"type
  defaultdefault fixedfixed /gt
• name the name of the attribute
• type the data type,
• default the attributes default value
• fixed a fixed value for the attribute
• For examle
• ltxsattribute nameGender typexsstring
  defaultfemale /gt

By convention, use xs for namespace for XML Schma
namespace
optional
14
ASSOCIATING ATTRIBUTES AND ELEMENTS

• The basic structure for defining a complex type
  with XML Schema is
• ltxselement name"name"gt
• ltxscomplexTypegt
• declarations
• lt/xscomplexTypegt
• lt/xselementgt
• name the name of the element
• declarations schema commands specific to the
  type of complex element being defined.

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
16
EMPTY ELEMENTS AND ATTRIBUTES

• The code to declare the attributes of an empty
  element is
• ltxselement name"name"gt
• ltxscomplexTypegt
• attributes
• lt/xscomplexTypegt
• lt/xselementgt
• attributes the set of declarations that define
  the attributes associated with the element

17
EMPTY ELEMENTS AND ATTRIBUTES

• For example
• ltxs element namesubjectgt
• ltxscomplexTypegt
• ltxsattriubute namename typexsstring /gt
• ltxsattriubute nameage typexsstring /gt
• lt/xs complexTypegt
• lt/xselementgt
• describes the following empty element
• ltsubject nameCynthia Dibbs age62 /gt

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.
• ltxselement name"name"gt
• ltxscomplexTypegt
• ltxssimpleContentgt
• ltxsextension base"type"gt
• attributes
• lt/xsextensiongt
• lt/xssimpleContentgt
• lt/xscomplexTypegt
• lt/xselementgt

19
SIMPLE CONTENT AND ATTRIBUTES
Indicates text but no child

• For example
• ltxselement nameperformancegt
• ltxscomplexTypegt
• ltxssimpleContentgt
• ltxsextension basexsstringgt
• ltxsattribute namescale
  typexsstring/gt
• lt/xsextensiongt
• lt/xssimpleContentgt
• lt/xscomplexTypegt
• lt/xselementgt
• defines
• ltperformance scaleKarnofskykgt0.81lt/performancegt
  

Extended to include an attribute
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
• requiredThe attribute must always appear with
  the element
• optional(default) The use of the attribute is
  optional with the element
• prohibitedThe attribute cannot be used with the
  element
• For example, the previous attribute declaration
  is modified as
• ltxsattribute namescale typexsstring
  userequired/gt

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
• ltxselement ref"elemName" /gt
• ltxsattribute ref"attName" /gt
• where
• elemName the name used in an element
  declaration
• attName the name used in an attribute
  declaration

22
REFERENCING AN ELEMENT OR ATTRIBUTE

• ltxsattribute namescale typexsstring /gt
• ltxselement nameperformancegt
• ltxscomplexTypegt
• ltxssimpleContentgt
• ltxsextension base xsstringgt
• ltxsattributegt refscale userequired /gt
• lt/xsextensiongt
• lt/xssimpleContentgt
• lt/xscomplexTypegt
• lt/xselementgt

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
• ltxselement name"name"gt
• ltxscomplexTypegt
• ltxscompositorgt
• elements
• lt/xscompositorgt
• lt/xscomplexTypegt
• lt/xselementgt
• where
• elements the list of simple type element
  declarations for each child element
• compositor defines how the child elements are
  organized.

24
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.

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USING COMPOSITORS

• ltelement nameaddressgt
• ltxscomplexTypegt
• ltxssequencegt
• ltxselement name street type
  xsstring/gt
• ltxselement name city type xsstring/gt
• ltxselement name state type
  xsstring/gt
• lt/xssequencegt
• ltxscomplexTypegt
• lt/elementgt

Must be in sequence
26
USING COMPOSITORS

• ltelement nameFamilygt
• ltxscomplexTypegt
• ltxsallgt
• ltxselement name Father type
  xsstring/gt
• ltxselement name Mother type
  xsstring/gt
• lt/xsallgt
• ltxscomplexTypegt
• lt/elementgt

Family may contain Father and/or Mother in no
particular order
27
SPECIFYING THE OCCURENCES OF AN ITEM

• ltxselement namepatient typexsstring
  minOccurs1 maxOccurs3/gt

28
WORKING WITH CHILD ELEMENTS AND ATTRIBUTES

• The code for a complex type element that contains
  both attributes and child elements is
• ltxselement name"name"gt
• ltxscomplexTypegt
• ltxscompositorgt
• elements
• lt/xscompositorgt
• lt/xscomplexTypegt
• attributes
• lt/xselementgt

29
CHILD ELEMENTS AND ATTRIBUTES EXAMPLE

• ltxselement namepatientgt
• ltxscomplexTypegt
• ltxssequencegt
• ltxselement reflastname/gt
• ltxselement reffirstName/gt
• lt/xssequencegt
• ltxsattribute refpatID userequiredgt
• lt/xscomplexTypegt
• ltxselementgt

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SPECIFYING MIXED CONTENT

• ltSummarygt
• Patient ltNamegtCynthia Davislt/Namegt was enrolled
  in
• the ltStudygtTamoxifen Studylt/Studygt on 8/15/2003.
• lt/Summarygt
• can be declared in the schema file using the
  following complex type
• ltelement name"Summary"gt
• ltcomplexType mixed"true"gt
• ltsequencegt
• ltelement name"Name" type"string"/gt
• ltelement name"Study" type"string"/gt
• lt/sequencegt
• lt/complexTypegt
• lt/elementgt

element contains both text and child elements
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
• xmlnsxsihttp//www.w3.org/2001/XMLSchema-instanc
  e
• xsiSchemaLocationpschema.xsdgt

Commonly used for XML Schema instances
Schema instance namespace
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
• xsinoNamespaceSchemaLocation"schema"

Schema instance namespace
33
Pause and breath
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.

35
UNDERSTANDING DATA TYPES

• This figure shows the 44 built-in data types

Page XML 168
Premitive types
Dates times
Derived Types
36
UNDERSTANDING DATA TYPES

• This figure shows a partial description of XML
  string data types

Page XML 169
37
USING DATA TYPES

• Examples
• ltxsattribute namepatID typexsID /gt
• ltxsattribute nameonStudy typexsstring /gt
• ltxsattribute namescale typexsstring /gt

38
UNDERSTANDING DATA TYPES

• This figure shows a partial description of XML
  numeric data types

Page XML 170
39
UNDERSTANDING DATA TYPES

• This figure shows a partial description of XML
  date and time data types

Page XML 171
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,

41
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.

42
LIST

• List data type is a list of values separated by
  white space
• To create a list data type
• ltxssimpleType namewbcListgt
• ltxslist itemTypexsdecimal /gt
• ltxssimpleTypegt
• To use the data type
• ltxselement namewbc typewbcList /gt
• ltwbegt15.1 15.8. 20.0 9.3 7.1 5.2 lt/wbcgt

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.

44
CONSTRAINING FACETS

• This figure shows the 12 constraining facets

45
CONSTRAINING FACETS EXAMPLE

• ltxssimpleType nameageTypegt
• ltxsrestriction basexsintegergt
• ltxsminInclusive value 21 /gt
• lt/xsrestrictiongt
• lt/xssimpleTypegt

Constrains the data type to be greater than or
equal to the value
46
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
• ltxssimpleType name"name"gt
• ltxsrestriction base"type"gt
• ltxspattern value"regex"/gt
• lt/xsrestrictiongt
• lt/xssimpleTypegt
• Where regex is a regular expression pattern.

47
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
• Etc.

48
PATTERN QUANTIFIERS

• This figure shows pattern quantifiers

49
EXAMPLE REGULAR EXPRESSIONS

• ltxspattern value\d3 /gt
• ltxspattern valueA-Z /gt
• ltxspattern valueA-Z0,10 /
• ltxsximpleType namemrTypegt
• ltsxrestrictiion basexsIDgt
• ltxspattern valueMR\d3-\d3-d22
  /gt
• lt/xsrestrictiongt
• ltxssimpleTypegt

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
• ltxselement namefullName"gt
• ltxscomplexTypegt
• ltxssequencegt
• ltxselement name"firstName"
  type"xsstring"/gt
• ltxselement name"lastName" type"xsstring"
  /gt
• lt/xssequencegt
• lt/xscomplexTypegt
• lt/xselementgt
• Use
• ltxselement nameclient typefullName/gt
• ltxselement namesalesperson typefullName/gt

51
NAMED MODEL GROUPS

• A named model group is a collection, or group, of
  elements.
• Syntax
• ltxsgroup name"name"gt
• elements
• lt/xsgroupgt
• Where name is the name of the model group, and
  elements is a collection of element declarations

52
NAMED MODEL GROUPS EXAMPLE

• Definition
• ltxsgroup namefullNamegt
• ltxssequencegt
• ltxselement name"firstName"
  type"xsstring"/gt
• ltxselement name"lastName" type"xsstring"
  /gt
• lt/xssequencegt
• lt/xsgroupgt
• Use
• ltxselement nameclient"gt
• ltxscomplexTypegt
• ltxsgroup reffullName/gtgt
• lt/xscomplexTypegt
• lt/xselementgt

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
• ltxsattributeGroup name"name"gt
• attributes
• lt/xsattributeGroupgt
• Where name is the name of the attribute group and
  attributes is a collection of attributes assigned
  to the group.

54
WORKING WITH NAMED ATTRIBUTE GROUPS

• Example
• ltxsattributeGroup nameDRInfogt
• ltxsattribute nameDRID typexsstring
  userequired /gt
• ltxsattribute namedept typexsstring
  userequired /gt
• ltxsattributeGroupgt
• ltxselement namedoctor typedeptData/gt
• ltxscomplexType name deptDatagt
• ltxssimplecontentgt
• ltxs extension base stringgt
• ltxsattributegroup
  refDRIinfo/gt
• lt/xsextensongt
• lt/xssimplecontentgt
• lt/xscomplexTypegt

ltdoctor DRIDDR251 deptPediatricsgt curt
Hurley ltdoctorgt
55
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

56
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

57
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.

58
FLAT CATALOG DESIGN
Figure 4-36 page 192
This figure shows a Flat Catalog design
59
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.

60
RUSSIAN DOLL DESIGN
Figure 4-37 page 193
This figure shows a Russian Doll design
61
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

62
VENETIAN BLIND DESIGN
Figure 4-38 page 194
63
COMPARING SCHEMA DESIGNS
Figure 4-39 page 195

• This figure compares the three schema designs

64
PLACING A SCHEMA IN A NAMESPACE TARGETING A
NAMESPACE

• To associate a schema with a namespace
• declare the namespace
• prefixxmlns"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

65
PLACING A SCHEMA IN A NAMESPACE TARGETING A
NAMESPACE

• Example (Figure 4-40)
• ltxsschema xmlnsxshttp//www.ww3.org/2001/XMLSch
  ema
• xmlnshttp/uhosp.edu/patients/na
• targetNamespacehttp//uhosp.edu/patien
  ts/nagt
• ltxs element namepatientsgt
• ltxscomplexTypegt
• ltxssequencegt
• ltxselement namepatient
  typepType
• Minoccurs 1
  maxoccursunbounded /gt
• lt/xssequencegt
• lt/xscomplexTypegt
• lt/xselementgt

Declare the namespace
Make the new namespace the target of the schema
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
  documents root element
• xmlnsxsi"http//www.w3.org/2001/XMLSchema-instan
  ce"
• xsischemaLocation"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.

67
APPLYING A SCHEMA TO A DOCUMENT WITH A NAMESPACE

• Example
• ltpatients xmlnsxsihttp//www.W3.org/200/XMLSchem
  a-instance
• xmlnshttp//uhosp.edu/patients/ns
• xsischemaLocationhttp//uhosp.edu/patients/
  ns patvb.xsdgt
• ltpatient patID MR890-041-02
• .
• lt/patientgt

68
INCLUDING AND IMPORTING SCHEMAS

• To include a schema from the same namespace, add
  the following element as a child of the schema
  element
• ltxsinclude schemaLocation"schema" /gt
• Where schema is the name and location of the
  schema file.
• To import a schema from a different namespace,
  use the syntax
• ltxsimport namespace"uri" schemaLocation"schema"
  /gt
• Where uri is the URI of the imported schemas
  namespace and schema is the name and location of
  the schema file.

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

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 e-mail with the subject Tutorial 4 Case
  Problem 1 by ltyour namegt to jim_at_larson-tech.com
  by Wednesday 1150 May 1