What is (the) definition of digital marketing? part 1

I strongly suspect that if people in the industry knew HOW to define digital marketing a lot of their lives would be easier. That is, it would be awesome if some affirmative claim existed instead of statements what what it is not, and inventing "wizard of oz"-type of concepts like "engagement" and "authenticity" that regularly conceal more than they reveal. The trouble really started a few years back, when marketers started taking web as a serious advertising & branding vehicle. Trouble is, it turned out that is not enough for digital agencies to define their area of expertise as "digital marketing" as opposed to "traditional marketing", which relies mostly on media buys in television, print, radio, and outdoors. In reality, "digital marketing" usually means just a little bit more than adapting the attention-based, get-the-most-eyeballs framework of traditional marketing to the digital medium, and developing content formats suitable for it. So as people's social behavior has changed, digital agencies unsurprisingly found themselves in the same crisis as their traditional counterparts. As a consequence, they are increasingly forced to come up with a new set of concepts and methods that define what "digital marketing" is. Also to invent the new language to talk about the evolving digital reality. But as of now, the situation seems to me to be something like this: 
"Would you tell me, please, which way I ought to go from here?" asked Alice.
"That depends a good deal on where you want to get to," said the Cat.
"I don't much care where--" said Alice.
"Then it doesn't matter which way you go," said the Cat.
"--so long as I get SOMEWHERE," Alice added as an explanation.
"Oh, you're sure to do that," said the Cat, "if you only walk long enough."
"But I don't want to go among mad people," Alice remarked.
"Oh, you can't help that," said the Cat: "we're all mad here. I'm mad. You're mad."
"How do you know I'm mad?" said Alice.
"You must be," said the Cat, "or you wouldn't have come here."