What:
This tool helps create scripts to migrate XML data from one version of
an XML schema to a later
version of the same schema. The tool creates these scripts by
differencing XSD files and emitting
XSLT 2.0 to automatically migrate XML data.
Where:
https://sourceforge.net/projects/xsdevolver/
Background:
The company I work for sells a shrink-wrapped application where we
save a workbook in an XML format according to a specified XSD schema.
Over time, we expect the format of this schema to change. We wanted a
way to help us diff schema versions as they evolve over time and
generate initial XSLT to migrate data from older versions of the
schema to newer versions of the schema.
Details:
Usage:
XMLSchemaEvolver SchemaVersion1.xsd SchemaVersion2.xsd
Output:
1. A schema diff showing what elements have been changed
2. XSLT to translate XML data from SchemaVersion1 to SchemaVersion2
How does it work?
The basic idea is this:
1) Do a diff of two xml schema (xsd) files.
2) Each change is classified as an INSERT, DELETE, MOVE or RENAME
operation.
3) For each of these operations, emit simple XSLT to carry out
the desired data change.
4) These data change operations are modeled after a set of
standard XSLT operations suggested by
Jesper Tverskov in XSLT Transformation Patterns. A full list
of the transformations emitted by our
code can be found XSLT Transformations.txt in the documentation folder.
Will this program do everything I will ever need?
Probably not. The point of this code is to automate simple changes
that are found via differencing. For large complex changes where you
need to map multiple values into a single value or massively change a
structure you will probably need a data mapping tool. However, this
code should help to automate many small simple changes and/or give you
starter code that you can build upon to implement more complex
changes.
Example
Suppose we start with the following simple schema to represent an address
(see employees.xsd in the Tests directory):
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema";
xmlns:emp="http://www.zephyrassociates.com/Zephyr/Employees";
targetNamespace="http://www.zephyrassociates.com/Zephyr/Employees";>
<xsd:complexType name="Locale">
<xsd:attribute name="region" type="xsd:string" default="US"/>
</xsd:complexType>
<xsd:complexType name="BaseAddress">
<xsd:complexContent>
<xsd:extension base="emp:Locale">
<xsd:sequence>
<xsd:element name="street" type="xsd:string"/>
<xsd:element name="city" type="xsd:string"/>
<xsd:element name="state" type="xsd:string"/>
<xsd:element name="zip" type="xsd:string"/>
</xsd:sequence>
</xsd:extension>
</xsd:complexContent>
</xsd:complexType>
<xsd:complexType name="Address">
<xsd:complexContent>
<xsd:extension base="emp:BaseAddress">
<xsd:sequence>
<xsd:element name="zip_plus_four" type="xsd:string"/>
</xsd:sequence>
</xsd:extension>
</xsd:complexContent>
</xsd:complexType>
</xsd:schema>
Now we want to rename the attribute in the base type “Locale” from
“region” to “country”. So, we have a new schema like
(employeesAttributeRename.xsd):
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema";
xmlns:emp="http://www.zephyrassociates.com/Zephyr/Employees";
targetNamespace="http://www.zephyrassociates.com/Zephyr/Employees";>
<xsd:complexType name="Locale">
<xsd:attribute name="country" type="xsd:string" default="US"/>
</xsd:complexType>
…
XMLSchemaEvolver will detect the change in the name of the attribute
and issue XSLT to change the name of the attribute in the base type
and any types that are derived as extensions of this base type
(Tests_Out_Expected\employeesAttributeRename_fwd.xslt):
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
xmlns:emp="http://www.zephyrassociates.com/Zephyr/Employees";
<xsl:import-schema
namespace="http://www.zephyrassociates.com/Zephyr/Employees";
schema-location="employees.xsd"/>
<xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
<!--
________________________
Final changelist after identifying renamed elements, moved elements,
and removing rearrangements that are not part of a sequence.
Note. Before we emit the XSLT we remove any inserted root elements or
types that did not exist in the old schema since we have no place to
put such elements.
________________________
________________________
Types. Renamed:
emp:Locale/@region ==> emp:Locale/@country
________________________
-->
<!--Identity transform-->
<xsl:template match="@*|node()">
<xsl:copy>
<xsl:apply-templates select="@*|node()"/>
</xsl:copy>
</xsl:template>
<!--Update the XML file to point to the new version of the schema-->
<xsl:template match="@xsi:schemaLocation">
<xsl:attribute
name="xsi:schemaLocation">http://www.zephyrassociates.com/Zephyr/Employees
employeesAttributeRename.xsd</xsl:attribute>
</xsl:template>
<!--Rename the attribute(s) below-->
<xsl:template match="element(*, emp:Locale)/@region">
<xsl:attribute name="country" select="."/>
</xsl:template>
</xsl:stylesheet>
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