[Metadatalibrarians] [xsl] Ann: XML Schema Evolver

[Dana Pearson]

This tool may be of interest to those working with evolving schema:

On Sun, May 30, 2010 at 8:54 PM, Corwin Joy <corwinjoy at gmail.com> wrote:
> 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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-- 
Dana Pearson
dbpearsonmlis.com