Defining a Physical Configuration FAQS

1. What is the difference between an expression and a condition?

• Expression: Used to define transformations or mappings in components like datastore, aggregate, or distinct.
• They return values with specific data types (e.g., VARCHAR, NUMERIC).
• Condition: Used in components like filter, join, or lookup to define boolean logic (TRUE/FALSE) that filters or controls how data is processed.

2. How do I define an expression or condition in the mapping editor?

• In the mapping editor, select the target attribute, and then modify the Expression or Condition field in the Property Inspector.
• You can use the Expression Editor for more advanced editing or drag and drop source attributes into the expression field to avoid errors.

3. What should I do if a source attribute is not highlighted when I click a target attribute?

• If a source attribute isn't highlighted, the expression might be invalid. 
• This could be due to a typo or an issue with the cross-reference. Double-check the expression for errors and ensure the correct source attribute is referenced.

4. Why should I use the Expression Editor instead of manually editing expressions?

• The Expression Editor ensures valid cross-references by providing a list of available source attributes in scope.
• It helps prevent manual errors like typos and simplifies the creation of expressions.

5. What does the "f" icon next to an attribute in the logical diagram indicate?

• The "f" icon indicates that a function (expression) is applied to the attribute. It serves as a visual cue to show that an expression is in place for that attribute.

6. Can conditions include window functions?

• No, window functions are not valid in filter conditions.
• Conditions must return a boolean value (TRUE or FALSE), and window functions do not meet this requirement.

7. How do I validate the correctness of my mapping?

• After making changes to expressions or conditions, you can validate your mapping by clicking the green check mark icon in the logical diagram.
• This will check for errors such as missing connections or empty expressions.

8. What is the scope of attributes in the Expression Editor?

• The Expression Editor only shows attributes that are in scope—meaning those that are connected in the mapping diagram.
• If there are no upstream or downstream connections, no attributes will be listed.

9. What happens if the expression editor displays no attributes in scope?

• This typically means the component you're working with has no connections to other components.
• Ensure that your component has upstream or downstream connections to other components containing attributes.

10. Can I have multiple expressions on a single attribute?

• Yes, components like the Set component allow multiple expressions on a single attribute.
• However, most other components (such as projectors) typically support only one expression per attribute.

11. Why aren't my changes in the Expression Editor taking effect?

• If your changes aren’t reflecting, ensure you’re saving or applying the modifications in the Expression Editor.
• Also, check for any validation errors that might prevent the expression from being accepted.

12. How do I know if my mapping is missing any connections or has errors?

• When validating your mapping by clicking the green check mark icon, validation will show any missing connections, empty expressions, or other issues that need to be corrected.

13. What types of components require conditions?

• Filter, Join, and Lookup (Selector) components require conditions to specify how the data should be filtered or joined.
• Conditions control the flow of data in these components based on boolean logic.

14. What types of components require expressions?

• Datastore, Aggregate, Distinct, and Projector components require expressions to perform data transformations or mappings.
• These components use expressions to calculate or modify attribute values.

15. What should I do if I encounter an error in an expression or condition?

• If you encounter an error, carefully review the expression or condition for syntax issues, missing attributes, or invalid references.
• The expression editor provides helpful feedback to guide you in resolving the issue.