The XSD Generation facility
converts a UML class model to a W3C XML Schema
(XSD). This allows Data Modelers to start working
at a conceptual level in UML, leaving the tedious
aspects of XSD creation to EA. The schema generation
can then be customized if necessary, by using
the provided "UML Profile for XML" as
described later.
An XML schema corresponds to a UML package. Therefore
the XSD generation is a package-level operation
in EA. To demonstrate the usage of the schema
generator, we begin with an example model.
Getting Started
To use the schema generation
facility you will require the following:
| •
|
EA Professional
or Corporate edition |
| • |
XSDDataTypes
Package: This package contains classes representing
XSD primitive data types. |
| • |
UML
Profile for XML: This resource file contains
the stereotyped classes which allow the schema
generation to be customized. |
Note:
the XSDDataTypes package
is available from the above link as an XMI file.
Once you have downloaded the file, use EA's "Import
from XML file" facility to import the package
(see more information in the EA helpfile under
Model Management | Import & Export | XMI |
Import from XMI).
Steps to Generate XSD:
| 1.
|
Select the
package to be converted to XSD by right-clicking
on the package in the Project Browser. |
| 2. |
Select Project | Generate
XML Schema from the main menu. |
| 3. |
Set the desired output
file using the Filename field. |
| 4. |
Set the desired xml encoding
using the Encoding field. |
| 5. |
Click on the Generate
button to generate the schema. |
| 6. |
The progress of the schema
generator will be shown in the Progress edit
box. |
Example
The following Class diagram models a simple "Employee Details" system, intended to store a company's employee contact information. The classes shown form the "EmployeeDetails" package. The UML attributes of the classes map directly to XML elements or attributes. Note that the classes have no methods, since there is no meaningful correspondence between class methods and XSD constructs.
The following figure shows the schema which is generated for the Employee Details package by default. Notice how each UML class corresponds to a complexType definition in the schema. The class attributes are generated as schema elements contained in a "sequence" model group within the definition. The enumeration class is the exception here- it maps directly to an XSD enumeration, contained within a simpleType definition.
<?xml
version="1.0" encoding="ISO-8859-1"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="Person"
type="Person"/>
<xs:complexType name="Person">
<xs:sequence>
<xs:element
name="Person.firstName" type="xs:string"/>
<xs:element
name="Person.surName" type="xs:string"/>
<xs:element
name="Person.birthDate" type="xs:string"/>
<xs:element
name="Person.gender" type="xs:string"/>
<xs:element
name="Person.contactDetails">
<xs:complexType>
<xs:sequence>
<xs:element
ref="ContactInfo"/>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
<xs:element name="Employee"
type="Employee"/>
<xs:complexType name="Employee">
<xs:complexContent>
<xs:extension
base="Person">
<xs:sequence>
<xs:element
name="Employee.status" type="Status"/>
<xs:element
name="Employee.jobTitle" type="xs:string"/>
<xs:element
name="Employee.startDate" type="xs:date"/>
<xs:element
name="Employee.department" type="xs:string"/>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
<xs:element name="ContactInfo"
type="ContactInfo"/>
<xs:complexType name="ContactInfo">
<xs:sequence>
<xs:element
name="ContactInfo.homePhone" type="xs:string"/>
<xs:element
name="ContactInfo.mobilePhone" type="xs:string"/>
<xs:element
name="ContactInfo.officePhone" type="xs:string"/>
<xs:element
name="ContactInfo.email" type="xs:string"/>
<xs:element
name="ContactInfo.streetAddress" type="xs:string"/>
</xs:sequence>
</xs:complexType>
<xs:simpleType name="Status">
<xs:restriction
base="xs:string">
<xs:enumeration
value="Full-Time"/>
<xs:enumeration
value="Part-Time"/>
<xs:enumeration
value="Casual"/>
<xs:enumeration
value="Contract"/>
</xs:restriction>
</xs:simpleType>
<xs:element name="EmployeeRecords"
type="EmployeeRecords"/>
<xs:complexType name="EmployeeRecords">
<xs:sequence>
<xs:element
name="EmployeeRecords.Employee">
<xs:complexType>
<xs:sequence>
<xs:element
ref="Employee" minOccurs="0"
maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:schema>
The following table describes the default mapping of UML constructs to XSD constructs. The next section describes a UML Profile for XML which allows this default mapping to be altered to suit individual needs. Using the profile, we will alter our example class model to tailor the generation of the XML schema.
| UML
Construct |
Default
XSD Production Rules |
| Package |
A schema
element is generated for the target
package. If the target package includes
classes from another package, which has
the tagged values “targetNamespace”
and “targetNamespacePrefix” set,
these are included as attributes of the
schema element.
In addition, an import or include element
is created for each referenced package.
(An include element is used if the external
package shares the same targetNamespace
tagged value as the target package. An import
element is used where the targetNamespaces
differ.) |
| Class |
A root-level element
declaration and complexType
definition are generated. The element name
and type
are the same as the class name. An XSD sequence
model group is generated to contain UML attributes
generated as elements. |
| Attribute |
An element
is declared for each class attribute. The
element name
is set to that of the UML attribute name.
This is prepended with the class name to make
the element unique. The minOccurs
and maxOccurs
attributes are set to reflect the attribute
cardinality. (Note: If left unspecified, minOccurs
and maxOccurs default to 1.) If the attribute
refers to another class, the element declaration
is followed a complexType definition, which
contains a reference to the appropriate complexType.
|
| Association |
An element
is declared for each of association owned
by a class. The element name
is set to that of the association role.
The minOccurs
and maxOccurs
reflect the cardinality of the association.
Note: if the direction of the association
is unspecified, the owner is assumed to be
the source. |
| Generalization
(Inheritance) |
For single inheritances,
an extension
element is generated with the base
attribute set to the base class name. The
UML attributes of the child class are then
appended to an all
model group within the the extension element. |
| <<enumeration>>
(stereotype) |
A simpleType
element is declared for the enumeration class
with the name
attribute set to the class name. A restriction
element is generated with base
set to string.
Each of the class attributes are appended
to the restriction element as XSD enumeration
elements with value set to the UML attribute
name. Any type specification for the UML attributes
will be ignored by the schema generator. |
UML Profile for XML
The UML profile for XML
specifies a set of stereotypes, tagged values
and constraints which may be applied to the UML
model in order to change particular aspects of
the resulting schema. For example, we may wish
to have certain UML class attributes converted
to XSD attributes or, we may need to use a different
model group than the default "sequence".
The stereotype explicitly
tells the generator to which XSD structure the
UML construct maps. The tagged values further
define aspects of the mapping, such as whether
the elements should be qualified. The constraints
define any conditions that must be satisfied for
the stereotype to apply.
To demonstrate how the profile
for XML can affect the schema generation, refer
to the following class diagram - an adaptation
of our previous example. Note the changes in the
corresponding schema.
<?xml
version="1.0" encoding="ISO-8859-1"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:simpleType name="Gender">
<xs:restriction
base="xs:string">
<xs:pattern
value="male|female"/>
</xs:restriction>
</xs:simpleType>
<xs:element name="Person"
type="Person"/>
<xs:complexType name="Person">
<xs:sequence>
<xs:element
name="Person.surName" type="xs:string"/>
<xs:element
name="Person.firstName" type="xs:string"/>
<xs:element
name="Person.birthDate" type="xs:string"/>
<xs:element
name="Person.contactDetails">
<xs:complexType>
<xs:sequence>
<xs:element
ref="ContactInfo"/>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:sequence>
<xs:attributeGroup
ref="Person.att"/>
</xs:complexType>
<xs:attributeGroup name="Person.att">
<xs:attribute
name="Person.gender" type="Gender"/>
</xs:attributeGroup>
<xs:element name="Employee"
type="Employee"/>
<xs:complexType name="Employee">
<xs:complexContent>
<xs:extension
base="Person">
<xs:sequence>
<xs:element
name="Employee.status" type="Status"/>
<xs:element
name="Employee.jobTitle" type="xs:string"/>
<xs:element
name="Employee.startDate" type="xs:date"/>
<xs:element
name="Employee.department" type="xs:string"/>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
<xs:element name="ContactInfo"
type="ContactInfo"/>
<xs:complexType name="ContactInfo">
<xs:sequence>
<xs:element
name="homePhone" type="xs:string"/>
<xs:element
name="email" type="xs:string"
maxOccurs="3"/>
<xs:element
name="streetAddress" type="xs:string"/>
<xs:choice>
<xs:element
name="mobilePhone" type="xs:string"/>
<xs:element
name="officePhone" type="xs:string"/>
</xs:choice>
</xs:sequence>
</xs:complexType>
<xs:simpleType name="Status">
<xs:restriction
base="xs:string">
<xs:enumeration
value="Full-Time"/>
<xs:enumeration
value="Part-Time"/>
<xs:enumeration
value="Casual"/>
<xs:enumeration
value="Contract"/>
</xs:restriction>
</xs:simpleType>
<xs:element name="EmployeeRecords"
type="EmployeeRecords"/>
<xs:complexType name="EmployeeRecords">
<xs:all>
<xs:element
name="EmployeeRecords.Employee">
<xs:complexType>
<xs:sequence>
<xs:element
ref="Employee" minOccurs="0"
maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:all>
</xs:complexType>
</xs:schema>
In particular:
| •
|
We have explicitly
set the stereotype for the Person and ContactInfo
classes to XSDcomplexType. EmployeeRecords
uses the modelGroup tagged value to use the
all construct instead of the default sequence.
The ContactInfo also uses the memberNames
tag to prevent the attribute's element names
being prefixed with the class name. |
| • |
The XSDattribute stereotype
causes the generation of an XSD attribute
(instead of the default element), for the
gender attribute of class Person. |
| • |
To restrict the possible
values for the gender attribute to "male"
or "female", we have created the
Gender class. Class "Gender" is
stereotyped XSDsimpleType and uses the pattern
tagged value to restrict its possible values.
We could also have used regular expressions
in this way to restrict values for the "birthDate",
"email" and phone number attributes.
|
| • |
The use of the XSDchoice
stereotype allows us to generate the "mobilePhone"
and "officePhone" attributes as
options within an XSD choice modelGroup. Note
how the memberNames of attributes contained
by this modelGroup are unqualified as determined
by its containing complexType class. (This
occurs for each owner of the modelGroup, where
the multiple associated classes.) |
| • |
Less obvious from the
diagram is the ordering of the attributes
for the Person class. Notice how the "firstName"
and "surName" attributes have had
their position swapped in the schema. This
is because the position tagged value has been
used for the attribute of the Person class
in the modified example. |
The following table details
the features of the UML Profile for XML. Tagged
value names are shown in bold followed by the
allowed values. If there is a default value used
by EA's schema generator it is underlined.
<<XSDschema>>
| UML
Construct |
Package;
Component |
|
Description |
All classes in a package or component are
defined within one schema. This stereotype
can be used to specify schema-wide settings.
|
|
Tagged Values |
anonymousRole:
( true | false ) |
Specifies if the role name is included in
the element declaration for the UML attribute
|
| anonymousType:
( true | false )
|
Specifies
whether the class type is anonymous for attributes.
|
attributeFormDefault:
( qualified | unqualified
) |
Determines whether attribute instances must
be qualified |
defaultNamespace:
|
The default namespace used in this schema.
This value is used to specify the default
namespace attribute (xmlns=), in the schema
element. |
elementDerivation:
( true | false ) |
Determines whether inheritances are generated
using XSD extension or copy-down inheritance. |
elementFormDefault:
( qualified | unqualified ) |
Determines whether element instances must
be qualified. |
memberNames:
( qualified | unqualified ) |
Determines whether elements generated from
Class attributes have their name qualified
by the corresponding class name. |
modelGroup:
( all | sequence | choice ) |
Specifies the default XSD model used to generate
complexType definitions. |
| schemaLocation:
|
The
URI which identifies the location of the schema.
This value is used in the import and include
elements. |
|
targetNamespace: |
The URI which uniquely identifies this schema's
namespace. |
|
targetNamespacePrefix: |
The prefix which abbreviates the targetNamespace. |
|
version: |
The version of this schema. |
| Constraints
|
None. |
<<XSDcomplexType>>
| UML
Construct |
Class |
|
Description |
complexType definitions are created for generic
UML classes. This stereotypes helps tailor
the generation of a complexType definition
|
|
Tagged Values |
|
memberNames:
( qualified| unqualified ) |
Determines whether elements generated from
the UML class attributes and associations
have their name qualified by the corresponding
class name for this complexType definition.
|
mixed:
( true | false ) |
Determines whether this element may contain
mixed element and character content. Refer
to the W3C XML Schema recommendation. |
modelGroup:
( all | sequence | choice ) |
Overrides the default XSD model for generating
this complexType definition. |
|
Constraints
|
None. |
<<XSDsimpleType>>
|
UML Construct |
Class |
|
Description |
An XSD simpleType is generated for classes
with this stereotype. |
|
Tagged Values |
|
derivation:
( restriction | list ) |
Specifies the derivation of the simpleType.
Refer to the W3C XML Schema recommendation.
|
|
length: |
Refer to the W3C XML Schema recommendation.
|
|
minLength: |
Refer to the W3C XML Schema recommendation.
|
|
maxLength: |
Refer to the W3C XML Schema recommendation.
|
|
pattern: |
Refer to the W3C XML Schema recommendation.
|
|
Constraints
|
This class can only participate in an inheritance
relation with another simpleType. It cannot
have any attributes or own any associations.
They will be ignored if present. |
<<XSDsequence>>
|
UML Construct |
Class |
|
Description |
The schema generator creates a sequence model
group as the container for the attributes
and associations owned by this class. The
model group is in turn added to the model
groups of this class' respective owners.
Note: Tagged values specified by owners of
this class persist through to the child elements
of this model group. Thus if memberNames are
unqualified for a complexType, so will be
the children of this model group when added
to that complexType. |
|
Tagged Values |
None. |
|
Constraints |
This class must be the destination of unidirectional
associations. If it is not, this class and
its connectors are ignored, possibly invalidating
other model group classes. Inheritance relations
are ignored for this class. |
<<XSDchoice>>
|
UML Construct |
Class |
|
Description |
Creates an XSD choice element. Refer to XSDsequence
for more details. |
|
Tagged Values |
None |
|
Constraints |
As for XSDsequence. |
<<XSDelement>>
|
UML Construct |
Attribute; AssociationEnd |
|
Description |
By applying this stereotype to a UML class
attribute or AssociationEnd, the corresponding
UML entity is generated as an element within
the parent complexType and not as an XSD attribute.
|
|
Tagged Values |
|
form:
( qualified | unqualified ) |
Overrides the schema's elementFormDefault
value. |
|
position: |
Causes the the elements to be ordered within
a sequence model group of the containing complexType.
Duplicated and invalid position tagged values
are ignored and result in undefined ordering
of the UML attributes. Missing position values
cause the defined positions to be allocated
as specified, with the remaining elements
filling the missing positions in an undefined
order. |
anonymousRole:
( true | false ) |
Specifies if the role name is included in
the element declaration for the UML attribute
|
| anonymousType:
( true | false ) |
Specifies
whether the class type is anonymous for attributes.
|
| Constraints
|
None. |
<<XSDattribute>>
|
UML Construct |
Attribute; AssociationEnd |
|
Description |
By applying this stereotype to a UML class
attribute or AssociationEnd, the corresponding
UML entity is generated as an XSD attribute
within the parent complexType and not as an
XSD element. |
|
Tagged Values |
|
form:
( qualified | unqualified ) |
Overrides the schema's attributeFormDefault
value. |
use:
(prohibited | optional | required )
|
Refer to the W3C XML Schema recommendation.
|
|
default: |
Refer to the W3C XML Schema recommendation.
|
|
fixed: |
Refer to the W3C XML Schema recommendation.
|
| Constraints
|
The attribute datatype should not refer to
a class specification, it will be ignored
otherwise. |
<<XSDany>>
| UML
Construct |
Class; Attribute
|
| Description
|
If applied to a UML attribute, an XSD anyAttribute
element is generated. If applied to a UML
class, an XSD any element is generated. |
| Tagged
Values |
|
|
namespace: |
Refer to the W3C XML Schema recommendation.
|
processContents:
( skip | lax | strict ) |
Refer to the W3C XML Schema recommendation. |
| Constraints
|
None. |
<<XSDrestriction>>
|
UML Construct |
Generalization
|
|
Description |
Overrides the default use of XSD extension
for inheritance and generates the child as
a complexType with a restriction element instead. |
|
Tagged Values |
None |
|
Constraints |
Applies only to UML class parent-child relations.
|
To Do:
| •
|
More
XSD stereotypes will be added to the profile
such as XSDattributeGroup, XSDgroup and XLink
support. |
| • |
More
tagged values will be added, such as allowing
suffixes for complexType and simpleType definitions. |
| • |
More
detailed logging of errors and warnings during
schema generation. |
| • |
Generalization
and Association are the only currently supported
connection types. Aggregation (and Composition)
will be added. |
Known Issues:
| • |
Only
limited inter-package support is currently
available. For example, a class which inherits
from multiple classes outside of the target
package does not get all base attributes.
|
Please
note that this functionality is available in EA
Professional and EA Corporate.
|
