The following documentation does not apply to versions 0.1 and 0.2 of the Registry. It only applies to the as yet unreleased version.
The Registry tracks three main 'entities', each with their own eponymous table in the database:
Most of the other tables consist of associations between individual records of differing types. There are also some tables representing minor entities (Sidhe Houses, for example). Obviously the database doesn't make such distinctions between tables; however, it is worth following the approach of the Registry application, which has the major entities as its entry points.
This document is not intended to explain the technical features of the database. Rather, it explains the what and why of the relationships between the entities.
A primitive schema diagram shows the main tables of the database. There is also a technical overview of the tables.
The Fae table creates the useful abstraction of a fae being. There are two types of such a being: a soul and an incarnation. There is no reality to this abstraction, no information in common between the two. It is useful because both fae souls and incarnations can do similar things, such as swear oaths. By having a fae being abstraction, there is a single table to look up any reference to a fae of either type.
Note: A fae incarnation is equivalent to a changeling character (Sidhe or otherwise) in the game rulebook. I have used the term incarnation because that more accurately represents the reality of a fae soul being associated with a mortal body. This encompasses those souls who have not undertaken the Changeling Way but still have a mortal body (most Sidhe, for example, but also Nockers).
Although the database treats all records in the Fae table as equal, a fae soul is the fundamental constituent of any fae being in the reality of the game world. Every incarnation is the incarnation of a particular soul, while a soul is not necessarily incarnated.
A brief history lesson is in order here. Before the Sundering, all the fae were these souls wandering about the Dreaming. They had bodies, sure, but they weren't mortal bodies and didn't matter that much. (These bodies are not represented in the Registry.) With the Sundering came the first incarnations, whereby a fae soul somehow associated itself with a mortal body. (These mortal bodies have mortal souls associated with them, but they're not interesting and are not represented in the Registry.) First it was Nockers who took on bodies; after the Shattering, it was almost all the fae, except for the Sidhe (except, among them, House Scathach). Finally, when the Sidhe returned in 1969, they incarnated. In all three cases, a different type of incarnation occured, and only the second is the Changeling Way.
All invariant characteristics of a fae being are associated with that fae being's Soul record. This includes Kith and (in the case of Sidhe) House. This means that if a House Gwydion Sidhe incarnates several times, each incarnation will be a House Gwydion Sidhe.
An incarnation is that being formed when a fae soul joins with a mortal body, by whatever means. Unlike a fae soul, which is almost immortal, an incarnation lasts for a finite amount of time. An incarnation ends with the death of the mortal body or some other permanent severing of the bond between fae soul and mortal body.
In the case of changelings, the binding is actually between the fae soul and the mortal soul. When the mortal soul is reincarnated, the fae soul is with it, and so another incarnation begins. However, the fae soul may not play an active role in the life of the incarnation until late in life, when the mortal undergoes chrysalis. Naturally, a mortal soul which is bound to a fae soul in this way cannot be bound with another fae soul.
It is, I guess, possible for a mortal body to serve as the 'host' for more than one fae soul (at different times!). This would be exceptional in the extreme, however - incarnations are rare and unincarnations which are not the result of the death of the mortal body much rarer; for the latter to happen, and the former to happen twice, is almost certain not to happen. Nonetheless, much as I think it might be a useful constraint to make the mortal_ID in the Incarnation table unique, it is not.
There are two types of oath, boringly called greater and lesser. Greater oaths are those which originated before the Sundering, and are binding on the fae soul. Lesser oaths were developed after the Sundering and are binding only for the incarnation which swears it. This is important for the database design because there are in fact two versions of some of the oaths, one greater and one lesser. Fealty is such a one - it used to be that a fae soul would swear an oath of fealty to another fae soul, and that was it, forever. After the Sundering, another oath of fealty was developed which was only for an incarnation. Does this mean there is a potential conflict between duty to an incarnation's lord and to the fae soul's lord? Indeed yes. The incarnations must have known this was a possibility, but what could they do in the absence of knowing who was who in those troubled times?
Actually, the situation is not quite as I've described. There weren't actually any incarnations, except for Nockers, until the Shattering, or a little before. It was only after the Shattering that matters got really confused. The Oath of Fealty example is only really applicable once the Sidhe return in 1969 and have no way of knowing exactly who they are (for reasons which, astronishingly, are not completely clear to me at the moment!).
