1. Towards Easier Data-Binding for Derived Values in Ecore-based Models
Dr. Bernhard Schätz Dr. Vincent Aravantinos Vadim Cebotari 1

2. Towards easier Data-binding for derived values in Ecore-based models
Motivation:
Different views of the same model for different stakeholders
Accounting
Statistics
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3. Towards easier Data-binding for derived values in Ecore-based models
Different views implies derived values
Definition: Derived value
Derived values are values of the model attributes that are computed from other model attributes.
Application of derived values:
allow to display different information for different stakeholders
are not persisted in the model
calculated and displayed in the views at runtime
→ avoidance of consistency problems in the model
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4. Towards easier Data-binding for derived values in Ecore-based models
Example: Insurance contract
Domain model: Insurance contract
Derived value: Pro rata premium
Pro rata premium = annual premium / payment
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5. Towards easier Data-binding for derived values in Ecore-based models
Editable Derived values:
Existing modeling tools do allow to define derived values, but these values are usually not easily changeable: you have to implement the reaction to change manually.
This is particularly problematic because it contrasts with the viewing of (derived) values which is mostly automatized (e.g., in tools like Sirius).
In many use cases editable derived values are a desired feature.
The user does not care if the value is derived or not, s(h)e just want to modify it!
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6. Towards easier Data-binding for derived values in Ecore-based models
What are the problems with derived values?
Difficult to determine the implication on the model when modifying them
Context- and domain-specific characteristics
Manual implementation is required
→ Big effort required
→ Concrete consequence in practice: DERIVED VALUES ARE NON-CHANGEABLE
What can we do?
Assume the user modifies a derived value. How should the software react to it?
→ There is no all-purpose solution: it must be context- and domain-specific.
We can nevertheless propose standard solution patterns:
'Warning': we let the user make any modification but display a warning if the modification yields inconsistencies in the view
'Rule': user modification entails automatic update of the model elements, according to some rule defined by the toolsmith
'Interaction': when attempting a modification, the user gets a dialog offering to modify the model elements of which the value derives
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7. Towards easier Data-binding for derived values in Ecore-based models
Our solution: model-based approach for editing derived values
IMPLEMENTATION
Smart Data-Binding Tool
(SmartDB Tool)
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8. Towards easier Data-binding for derived values in Ecore-based models
Architecture of SmartDB Tool
EMF
Ecore
SmartDB Metamodel
Domain model
SmartDB Model
SmartDB View
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9. Towards easier Data-binding for derived values in Ecore-based models
Using SmartDB Tool - Roles
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10. Towards easier Data-binding for derived values in Ecore-based models
‘Warning‘ - Model-based definition
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11. Towards easier Data-binding for derived values in Ecore-based models
‘Warning‘ – Editing of derived value
User changes the receipt date to
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12. Towards easier Data-binding for derived values in Ecore-based models
‘Warning‘ – Editing of derived value
User wants to keep the change of the receipt date to
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13. Towards easier Data-binding for derived values in Ecore-based models
‘Rule‘ - Model-based definition
Model-based definition of the rule:
Annual premium = pro rata premium * payment method
The change of the derived attribute pro rata premium, computed as annual premium / payment method, will lead to the modification of the annual premium according to the above rule defined by the toolsmith. The payment method remains unchanged.
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14. Towards easier Data-binding for derived values in Ecore-based models
‘Rule‘ – Editing of derived value
View-based editing of derived value
Rule for editing of derived value pro rata premium:
Annual premium = pro rata premium * payment method
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15. Towards easier Data-binding for derived values in Ecore-based models
‘Interaction‘ - Model-based definition
Model-based definition of interaction:
Tariff calculated premium should be adjusted
Tariff calculated premium = tariff annual premium / (1.0 + risk premium rate)
Risk premium rate should be adjusted
Risk premium rate = (tariff annual premium / tariff calculated premium) – 1.0
By changing the derived attribute tariff annual premium, computed as tariff calculated premium * (1.0 + risk premium rate), the user can decide which of both attributes tariff calculated premium or risk premium rate should be adjusted according to the above formulas. The value of the other attribute should then be specified by the user in an interaction dialog.
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16. Towards easier Data-binding for derived values in Ecore-based models
‘Interaction‘ – Editing of derived value
The user wants to change the value of the derived attribute tariff annual premium to 1416,0
View-based editing of derived value
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17. Towards easier Data-binding for derived values in Ecore-based models
‘Interaction‘ – Editing of derived value
The user wants the risk premium rate to be adjusted to the new value of the tariff annual premium by setting tariff calculated premium to the value of 1200,0
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18. Towards easier Data-binding for derived values in Ecore-based models
‘Interaction‘ – Editing of derived value
The new risk premium rate is calculated and displayed in the view.
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19. Towards easier Data-binding for derived values in Ecore-based models
DEMO
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