I tripped across a good intro to DID/MPD. It goes nicely beyond the typical 1-pager of regurgitated information floating around the internet. (Not that the other stuff is wrong, it is just sterile, introductory, and overused.)

The article is called What is Dissociative Identity Disorder / Multiple Personality Disorder from the website Empty Memories, about PTSD and DID.

The article describes alters, their development, and switching in a positive way using nomenclature from Hart; Nijenhuis, Steele. They classify parts of the system as either the host or an A.N.P.’s (Apparent Normal Personality), with one or more E.P.’s (Emotional Personality) alters. The EP alters are those who lived through the traumas and are more hidden in the system. ANP(s) are sometimes unaware of the trauma or “phobic” to it, and often function separately. EPs can respond to the triggers, can be “stuck back” at the time of the trauma. Sometimes they are extremely well hidden behind another EP or ANP. The structure of the entire system can become quite complicated.

The article also address switching, therapy, diagnosis, and hearing voices.

While it is not a long article, it does have some good information that goes beyond the typical, helping to make DID explainable as less a disorder and more a normal reaction to trauma.