how to add more simple products into configurable products using magento API

Question

How can I simply add new simple products incrementally to configurable products?

or do I still need to retrieve the 2 original arrays of the pre-defined configurable product (getConfigurableAttributesData and getConfigurableProductsData) first, append the new arrays and set them again? Is it worked for my case just as the first-time creation?

And if the new simple product owns a new attribute / attribute options, do I also need to create /edit the attribute first before adding?

Thanks in advance!