Types of exceptions in Appian

The best way I've found to understand errors is to consider the Process Errors page in the documentation. It's very similar to what you mentioned, but it describes the three types of errors slightly differently:

• Errors on unattended nodes - A good example of this is that you could have an expression defined in a script task where the goal is to save some data into a variable. However, maybe there was a syntax error in your expression and it failed to evaluate. In this case, any other active flows will continue as usual, but the current flow is stopped at the errored node until the issue is resolved.
• Errors on attended tasks - A good example of this is suppose you had a task that you planned to assign to a user, and in the node you planned to assign the task to the current value of variable. However, on this execution of the process, suppose the variable is null. In this case the task cannot be assigned so an error occurs. In this case, the process is paused based on the exception.
• Transitory errors - These essentially include any other kind of errors. For example, suppose you're using the Call Web Service Smart Service. If you make a request and it receives a 408 timeout response, it will retry the request. The process itself won't show

If you're interested in understanding more about potential issues with processes, I'd highly recommend checking out some other pages in the documentation including:

• Automatic Error Handling
• Troubleshooting Process Models
• Monitoring and Editing Processes

The best way I've found to understand errors is to consider the Process Errors page in the documentation. It's very similar to what you mentioned, but it describes the three types of errors slightly differently:

• Errors on unattended nodes - A good example of this is that you could have an expression defined in a script task where the goal is to save some data into a variable. However, maybe there was a syntax error in your expression and it failed to evaluate. In this case, any other active flows will continue as usual, but the current flow is stopped at the errored node until the issue is resolved.
• Errors on attended tasks - A good example of this is suppose you had a task that you planned to assign to a user, and in the node you planned to assign the task to the current value of variable. However, on this execution of the process, suppose the variable is null. In this case the task cannot be assigned so an error occurs. In this case, the process is paused based on the exception.
• Transitory errors - These essentially include any other kind of errors. For example, suppose you're using the Call Web Service Smart Service. If you make a request and it receives a 408 timeout response, it will retry the request. The process itself won't show

If you're interested in understanding more about potential issues with processes, I'd highly recommend checking out some other pages in the documentation including:

• Automatic Error Handling
• Troubleshooting Process Models
• Monitoring and Editing Processes