Process Model Properties within Appian are referred to using the pm! domain prefix in process model expressions. This includes metadata such as the creator, name, or description of the process model.
Reference:
Appian Documentation: Process Model Properties

The best practice for naming variables in Appian is to use clear and descriptive names that convey the purpose or content of the variable. Therefore, local!applicantHeight is the best option as it precisely describes the value contained by the variable, which is the height of an applicant. This naming convention aids in readability and maintainability of the code, making it easier for developers to understand and modify the code in the future.
Reference: Appian Best Practices - Expression Writing and Naming Conventions

To define record type relationships in Appian, it's required that the record types have data sync enabled. This is necessary to ensure that the data is readily available in Appian for the relationships to be established and maintained.
Reference:
Appian Documentation: Record Type Relationships

Given that ri!name is defined as "Maria" and ri!directory contains two a!map() structures, one of which includes the name "Maria," the expression wherecontains(ri!name, index(ri!directory, "name")) will evaluate as follows: The index() function will return a list of values from ri!directory for the key "name," which will be {"Maria", "Steven"}. The wherecontains() function will then check where "Maria" is found within this list. Since "Maria" is the first element, the function will return a list of indices where "Maria" is found, in this case, {1}. Appian lists are 1-indexed, so the first position is represented by 1, not 0.
Reference: Appian Expression Language Documentation - Functions

An Appian best practice for calling interface rules within your interfaces is to always use a consistent ordering of rule parameters. This practice enhances the readability and maintainability of your interfaces, ensuring that other developers can understand and modify the interface more easily.
Reference:
Appian Documentation: Designing Interfaces