generating xml schemas from a logical data model (edw 2011)

1. Generating XML Schemas from a canonical model - a practical example
George McGeachie
Metadata Matters Limited
Enterprise Data World
Chicago
April 5th, 2010

2. The C word
Managing XSDs using a master (canonical) XML schema
The flexibility of PowerDesigner
The XML Schema Model in PowerDesigner
Which Canonical Model Should You Use?
Factors To Be Considered
Generating XML Models in Power Designer
Enterprise Data World, Chicago, April 5th 2011
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3. About Me
Ive been involved with modelling and managing data and metadata for longer than I care to remember.
When I first came across XML Schemas, I was struck by their simplicity and versatility. When I saw how some people use them, I realised that the days of unmanaged COBOL copybooks had returned to haunt me.
This is my attempt to exorcise the XML demon.
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4. The C word
Its difficult to avoid the word Canonical when discussing standard XML messages
To some, the message schemas are the canonical
To others, the underlying model is the canonical
When I use the word, I mean both of them
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5. Managing XSDs using a master (canonical) XML schema
An XML master schema must be hierarchical
It cannot easily show all the complex relationships between the data concepts
It cannot be flexible enough to support multiple views of the data
You need to understand XML to create, edit or read the model
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6. Managing XSDs using a master (canonical) XML schema
How would we integrate the metadata represented by a schema with our other metadata?
Reverse-engineer it into a repository or modelling tool?
How would we
Ensure consistency of XSDs with each other?
Enable impact analysis?
Manage the variations necessary between dependent schemas?
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7. The flexibility of PowerDesigner
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PowerDesigner has a dedicated XML Schema Model
Several different approaches supported out of the box
Generating XSDs from a class model
Generating an XML Schema model from a class model or a physical data model, then generating XSDs
Reverse-engineering existing XML Schemas into a class model or XML Schema Model
Can then generate a logical or conceptual view
8. Generation options in PowerDesigner
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9. The XML Schema Model in PowerDesigner
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This can link to an XML model, or an XSD
Referenced
Elements (in another XSD)
Complex Type
Note the XML-specific object types
10. XML-specific Model Objects
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Heres the detail of one of the sequences in the schema
Filter the displayed properties
Add additional items to the sequence
11. The XML Model
Dedicated to modelling XML Schema
1 schema per XML model, traceable to source models
Mapping Editor drag and drop mappings between models
Supports XSD, XDR and DTD
Multiple Namespaces supported
Can use 1 XML model for multiple schemas in the same target namespace
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12. The flexibility of PowerDesigner
Linkages are automatically maintained between models as you generate them
Additional mappings can be added between any two models
The generation process can be customised
You have control over the naming standards and data types used in each model
Impact and Lineage analysis is enabled by the generation and mapping links
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13. Generation Links
For each model, you can trace links to other models in the generation sequence
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14. Mapping Editor
Visually check mappings
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15. Impact of deleting XML Attribute - diagram
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Dependencies between PDM tables
PDM Tables mapped to the Element
Our attribute
XML Element
Simple Type (no longer required)
Remember:this diagram traces back to the model the XML attribute was generated from; in this case, the XML model was generated from a PDM, so the impact analysis traces to the PDM
16. Visible Links Between Models
Using the project feature, we can see the links between models
We can also include external objects, and create our own links to them
An XSD and an HTML file in this case
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17. Which canonical model?
One (or more) that you can sell within your organisation
Standard models
Standard Universal Data Models
e.g. IBM, Teradata, Oracle, EWS Solutions, Len Silverstons Universal Data Models
Industry Universal Data Models
e.g. standard messaging structures, such as from the OAG
See www.industrydatamodels.com
Some organisations use several of these, which will need to be cross-referenced
Your own model(s)
possibly used to extend one of the above
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18. A simple example of a relational canonical model
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This is an amended version of the Project Management PDM supplied with PowerDesigner
19. The Team Members schema
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20. The Project schema
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21. Factors To Be Considered
Generating a Type Library vs. generating Schemas
Physical Design Challenges
Model Management Challenges
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22. Generating a type library
often straightforward to generate
no structure
manual control of re-use in schemas
"let the service people design the schemas"
no impact analysis across schemas
may be the only acceptable first step
low impact on work patterns
gains initial acceptance of the role of a canonical model
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23. Generating Individual Schemas
A 'container' for each schema
Model, Submodel, Subject Area, Package etc
defines scope
provides documentation
facilitates governance
Complete generation
Nothing changed post-generation
Requires high degree of control over generation process
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24. Generating Individual Schemas
all types can be local
no need to 'include' or 'import' a base schema
the 'standard' types are used to generate the schema, rather than being referred to by the schema
The standard types are in the canonical data model
potential for impact analysis
can choose when to update each individual schema
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25. Sample Message Schema
This was generated from the same data model as the type library; it only contains what the message actually needs
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26. Physical Design Challenges
Some of these challenges are similar to those we face when we use a single Logical Data Model for designing multiple database schemas
Differences between Schemas
Handling Sub-types and inherited attributes
Denormalising attributes and entities
Data Type and Name conversions
Scalability of Process
Automating & future-proofing the generation process
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27. Model Management Challenges
Multiple reference models require careful consideration
E.g. Using OAG messaging standard as a reference model, extending it where required
Provides a quick-start for defining schemas
Be careful what you remove; perhaps remove nothing
How do you identify the parts that are actually in use?
How do you know what extensions are needed?
Have to map the standard to your own models
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28. Generating XML Models in PowerDesigner
Two options
Generate XML Model using default options, from selected tables, and tinker the XML afterwards
Use XML Builder to design and generate almost exactly what is required, and then tinker the XML model
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29. Contact Me
Telephone: +44 (0) 20 8123 8756 (forwarded to mobile)
UK mobile: +44 (0) 794 293 0648
Skype: gmcgeachie
Twitter: metadatajunkie
Email:George.McGeachie @ MetadataMatters.com
Blog: http://metadatajunkie.wordpress.com/
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30. Thanks for listening

generating xml schemas from a logical data model (edw 2011)

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