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It's unavoidable that

It's unavoidable that different applications will use different tools to render from raw. No matter how the information is saved, there will be tags attached to images that other applications can't make use of. Get used to it. The most important thing is that data is preserved and accessible.

As to what is the use of DNG. I'd say the following:

1. An openly structured raw data container that can be used to hold the image data, as well as other stuff described below. Apple can currently make use of this to render raw filetypes it has never seen before.
2. A way to attach all the rendering instructions and color profiles needed to replicate a user's intention for image rendering. This is particularly important as users will begin to render images with custom profiles to create distinctive looks. If the profiles don't travel with the files, the rendering cannot be replicated, even on software of the same version. This is something you need to get a better understanding of.
3. A way to attach one or more fixed renderings to a raw file container that is not application-specific in any way, and lets the user employ multiple raw converters in an archive, and bring the renderings along. It also allows the use of third-party asset management software that can correctly render the files. Lastly, it enables the user to leave the program entirely and take the renderings with him.
4. A raw data container that metadata can be written to in a safe and documented manner, unlike proprietary raw files.
5,. A format to save rendered filetypes in when they are edited parametrically. This is starting to be a large problem, and is going to grow larger fast.
6. A way to make image files self-validating in a way that can survive subsequent changes to the metadata or image settings. No other graphic file format offers anything like this.

I consider these to be extremely important facets of image archiving.

It is not, and never has been, intended as a way to standardize the raw rendering output.

Again, any input on what specifically needs changing in the spec, or in the applications that create DNG is most welcome. If there is specific information you need from a DNG that you can't get, that would be helpful to know. It would also be good if you corrected the inaccuracies in your article before it spreads too far around the internets. Like I say, battling these misconceptions makes a lot of needless work for me.