I think you two are wrong. Skeumorphism is about ornamental design, about design features that imitate something that was once necessary but is no more.
It’s consequently all about style, not about function (at least when it comes to real-world objects). Wikipedia has examples like flame shaped lightbulbs, artificial film grain or spoke patterns on hubcaps.
It seems that when it comes to software, skeumorphism can also refer to functional adoptions of virtual interfaces to their real-world counterparts†, but I think it would be misguided to exclude mere style here.
I mean, in the end this is a stupid semantic argument. Using leather textures is what it is, whether it’s skeumorphism or just style, but you two certainly do not have the facts on your side.
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† It’s pretty clear why that is the case: it’s only possible to make lightbulbs look like flames, not to make them work like flames. Software provides more freedom and makes it possible to make something virtual work like the real thing.
If we're going by the wikipedia page, here's their definition they provide:
"skeuomorphism is when a product imitates design elements /functionally necessary/ in the original product design, but that becomes ornamental in the new product design."
So yes, it is about function.
And also, the three things you mention are directly related to the function of the original objects. While these things are clearly used ornamentally in modern devices, their existence/use was inherent in the design of the modern devices' predecessors.
I think you misunderstood me. While it can be purely stylistic in the modern interpretation, the element replicated must have some functional purpose in the original. I do not think that you have to reimplement the functionality, that was just the example I used.
Your examples are skeumorphic because they use functional aspects of the original. "Find My Friends" is not skeumorphic because even if such a thing as "Find My Friends" existed in a previous form, the leather has nothing to do with its function.
If that sounds confusing to you, then I don't know what else to say. You're wrong?
Almost all aspects of a physical object are "functional", so this is a strange distinction to make.
For example, the rich Corinthian leather of a desk calendar functions as an arm rest and also functions as a binding mechanism for the calendar pages within. The stitching of said leather functions to hold the piece together.
The point is that you do not need rich Corinthian leather to make a desk calendar; in fact the vast majority of desk calendars in the world do not have any leather on them at all. Even on the real-world object, the choice to use leather serves a decorative purpose--it is not a functional necessity. Yet I've never heard someone call a leather desk calendar "skeuomorphic."
But is it necessary? That's an important part of the definition. For instance, the wood on Newsstand doesn't make it skeumorphic, but the bookshelf design does.
And again, where is the original product design for Find My Friends? Why did I never hear about anyone using a leather-bound location diviner before?
It’s consequently all about style, not about function (at least when it comes to real-world objects). Wikipedia has examples like flame shaped lightbulbs, artificial film grain or spoke patterns on hubcaps.
It seems that when it comes to software, skeumorphism can also refer to functional adoptions of virtual interfaces to their real-world counterparts†, but I think it would be misguided to exclude mere style here.
I mean, in the end this is a stupid semantic argument. Using leather textures is what it is, whether it’s skeumorphism or just style, but you two certainly do not have the facts on your side.
—
† It’s pretty clear why that is the case: it’s only possible to make lightbulbs look like flames, not to make them work like flames. Software provides more freedom and makes it possible to make something virtual work like the real thing.