Model Transformations

1. Model Transformations Colin Clark Antranig Basman

2. Bridging between views • Users view the world in terms of their needs • Solution developers view the world in terms of what they can provide • We need a system for smoothly transferring information back and forth between these worlds

3. A Preferences Statement • { • "display": { • "screenEnhancement": { • "fontSize": 24, • "foregroundColor": "white", • "backgroundColor": "black", • "magnification": 2.0, • "tracking": "mouse", • "invertImages": true, • "showCrosshairs": true • } • } • } A JSON document – in this case following the Access4All Specification (ISO 24751)

4. A Solution’s Settings (Linux) • “org.gnome.desktop.a11y.magnifier”: { • “mag-factor”: 2.0, • “mouse-tracking”: “centered”, • "showCrosshairs": true • }

5. This Simple Case: • General format: • This is a simple example of a transformation document { "mag-factor“ : "display.screenEnhancement.magnification“ } "<output path>": "<input path>"

6. Three important advantages Transformation documents make it — easier to figure out how to reverse the transformation easier to produce tools for authoring and visualisation easier to store, retrieve and parse in database technologies “lift” a transformation of documents into the corresponding transformation of schemata

7. Inverting this document • Simply flip keys and values • Not this easy in general! { “display.screenEnhancement.magnification” : "mag-factor“ }

8. Lenses in the Literature Aaron Bohannon, Jeffrey A. Vaughan, and Benjamin C. Pierce. Relational Lenses: A Language for Updateable Views. In Principles of Database Systems (PODS), 2006. Extended version available as University of Pennsylvania technical report MS-CIS-05-27. [ bib | tech report | .pdf ] Benjamin C. Pierce. Foundations for Bidirectional Programming, or: How To Build a Bidirectional Programming Language, June 2009. Keynote address at International Conference on Model Transformation (ICMT). [ bib | slides ]

9. Lifting (all documents) Lens for Schemas Schema A Schema B Governs Governs LIFT! Lens for Documents Document B Document A

10. The next class of issue User and solution don’t share the same value scale: • “$HKEY_CURRENT_USER\\Software\\Microsoft\\ScreenMagnifier”: { • “Magnification”: 200, [REG_DWORD INT] • “Invert”: 1 [REG_DWORD BOOL], • "FollowMouse": 1 [REG_DWORD BOOL] • } User uses a scale factor – solution uses a percentage

11. Transformation Lenses • Data-oriented • Declarative and functional • Bi-directional • Useful collection of lenses out of the box • Can be extended with new transformers • AT integrators don’t have to write code

12. A Transformer Function Is just a • gpii.transformer.scaleValue = function (value, expander, expandSpec) { • var factor = (expandSpec.factor === undefined ? 1.0 : expandSpec.factor); • return value * factor; • }; Implemented as a standard JavaScript function, with a global name and a particular signature: As well as the function, you need a little metadata to describe it to the system: fluid.defaults("gpii.transformer.scaleValue", { gradeNames: "fluid.standardTransformFunction" });

13. Standard “function grades” fluid.function • Inheritance of documents, not types – unlike in C++, this diamond works : ) fluid.transformFunction fluid.standardInputTransformFunction fluid.standardOutputTransformFunction fluid.lens fluid.standardTransformFunction

14. In context in a transformation record (Windows) • "capabilitiesTransformations": { • "Magnification": { • "expander": { • "type": "gpii.transformer.scaleValue", • "inputPath": "display.screenEnhancement.magnification", • "outputPath": "value", • "factor": 100 • }, • "dataType": { • "expander": { • "type": "fluid.model.transform.literalValue", • "value": "REG_DWORD" • } • } • }, • ...

15. Transform (Linux) • "capabilitiesTransformations": { • "mag-factor": "display.screenEnhancement.magnification", • "show-cross-hairs": "display.screenEnhancement.showCrosshairs", • "mouse-tracking": { • "expander": { • "type": "fluid.model.transform.valueMapper", • "inputPath": "display.screenEnhancement.tracking", • "options": { • "mouse": { • "outputValue": "centered" • } • } • } • } • }

16. Making choices – the ValueMapper • "mouse-tracking": { • "expander": { • "type": "fluid.model.transform.valueMapper", • "inputPath": "display.screenEnhancement.tracking", • "options": { • "mouse": { • "outputValue": "centered" • }, • “caret”: { • “outputValue”: “none” • } • } • } • }

17. Dumping Values – The Literal Value Transform • "<output path>": { • "expander": { • "type": "fluid.model.transform.literalValue", • "inputPath": "This will literally be the output." • } • }

18. Source Code • https://github.com/GPII/universal • The Model Transformation System • (Fluid Infusion github): • http://bit.ly/LaXMbJ • Preferences statement: http://bit.ly/LN4iEB • Settings Handler: http://bit.ly/M6mDfD • Solutions Registry: http://bit.ly/KrLo6Z

19. Questions? Colin Clark e: cclark@ocad.ca t: @colinbdclark Antranig Basman e: amb26@ponder.org.uk fluidproject.org gpii.net