Ductoria, dustoria, are transliterations of the arabic dusturiya which signifies a position of power. The ptolemaic, doryphory (spearbearer) refers to the same astrological configuration.
Ductoria refers to a planet rising before the Sun (oriental). It can also refer to a planet rising after the Moon (occidental). Some authorities say that this condition is given when the planet rises shortly before the Sun in the same or next sign or when it rises after the Moon in the same or next sign. If the planet is not in its domicile or exaltation it must be out of combustion.
If one thinks about it, this is a minor dignity at most and need only be taken into account if it somehow is dominant in the chart. The only possibility where it makes sense to say that this configuration shows a postion of power in reference to the Sun is if the planet is in its own domicile or exaltation — when considering what a strong debility combustion is. It makes sense here as in this situation the planet receives the Sun in its own sign and so this has something of the character of mutual reception.
I think that generally it is not necessary to clutter ones understanding with too much terminology. A good grounding in basic astrological symbology and a portion of common sense leads one to the same conclusion.
Maybe one added point might be helpful. One might ask why must the planet be oriental for the Sun and occidental for the Moon? Most readers are familiar with establishing theTemperament astrologically. Planets that are oriental to the Sun are able to express their nature more fully because they have something of the nature of a “morning” star. They are able to show their light more fully. A morning star is only visible if it rises before the Sun. The same applies to the Moon. Here the said planet is like an “evening” star. It rises after the Moon and so accompanies her at a decent distance, like a “spearbearer” or guard of honor.
So if cold and leaden Saturn were to act as a “morning star” his best chance to be noticed would be before sunrise and if he is not in Libra, Aquarius or Capricorn he had better make sure he isn’t combust. Saturn especially, is not at his best if his backside is burning! 😉
And while I am “expounding” I would also like to point out that it is all to easy to get caught up in terminology (please, no reproach intended as I am also not exempt from this!). When in doubt or in need of clarification or if the older texts seem too obtuse it is always helpful to consider the celestial phenomena itself. How does it look like in the sky? If we were to draw our charts in sand as the Astrologer in “An Analogy from Astrology”* in Attar’s “Parliament of the Birds” we would be more mindful that the chart is only a semblance, it helps us to focus our interpretative faculties, nothing more.