Here is another really good resource in understanding what DDNOS is, and how it’s classified at the professional level. Again, for me, this is the classification of Dissociation that I have. I don’t exhibit any specific symptom that puts me in a complete state of Dissociative Amnesia, Dissociative Identity Disorder, or Depersonalization/Derealization. But that doesn’t make my version of Dissociation any less important or difficult to live with than another of the others. It’s very real, as anyone who has a type of Dissociation knows.
The first example presentation of Other Specified Dissociative Disorder is very similar to the DSM-IV’s first example of Dissociative Disorder Not Otherwise Specified (DDNOS). Both these describe a form of complex dissociative disorder which is very similar to Dissociative Identity Disorder, but falls just short of meeting the criteria. OSDD example 1 is either identity disturbance with less distinct parts than in Dissociative Identity Disorder (they cannot physically take executive control over the person’s body, but strongly influence the person’s thoughts and actions and amnesia is present), known as DDNOS-1a :409, or distinct dissociative parts (alters or alternate identities) exist and can take executive control, but without amnesia,  known as DDNOS-1b.:409 However, the slightly changed wording for Dissociative Identity Disorder means that some people who previously were diagnosed as DDNOS-1 will now be diagnosed with Dissociative Identity Disorder. The two relevant changes involve the fact that identity alteration (changing identities between different personality states/alters/alter identities) can be self-reported or reported by a family member of friend rather than just clinical staff, and secondly a slight broadening of the amnesia criterion.
You can check out the full explanation with a lot of helpful information on this page on TraumaDissociation.com. Which is a very helpful and informative resource I’m finding, I highly recommend it.