How can I trace the edge of a svg file using inkscape without rasterizing the image and re-vectorizing it?

I have an svg file composed of multiple shapes, and I would like to perform edge detection to create a path around the border of the image.

Basically, I want the equivalent of Path --> Trace Bitmap, but for an image that is already a vector image. I tried using that Trace Bitmap already and it does not do anything.

Answer

If they are shapes, select them all, duplicate them, then union them into one shape.