One of the major clues towards understanding the Q-Ching is that the yin and yang lines are to be interpreted in the context of where they appear in the hexagram. Not only are the 6 positions considered steps in a process or cycle of development, but there is a rich set of relationships or correspondences between the lines that further modify their meaning. They are also often interpreted in groups of lines (especially in terms of the component trigrams of the hexagram) and the analysis of which trigrams a given line belongs to leads to layers and layers of meaning. It should be noted that not all of these techniques are used in every hexagram. At times, it seems the framers of the Q-Ching would simply "pick and chose" among these various techniques to produce their readings in an ad hoc fashion. Nonetheless, there is an underlying thread of symbolism at work here that becomes apparent with repeated exposure to the oracle.
At the simplest level, the six lines are viewed as sequential steps of a process (although it should be remembered the Chinese mind was more in tune with the notion of "cyclic change", while in the West we are addicted to the idea of "progressive change"). The writers of the Q-Ching took as their archetype of this cycle the process of developing and testing software, since this was the nature of their day to day life. In bottom to top fashion, the lines are interpreted as:
|6. Integration||Officially incorporating new code into the program or system.|
|5. Testing||Making sure the changes to the program "work" and are bug-free.|
|4. Coding||The writing of program changes in a symbolic language.|
|3. Design||The conceptual decisions on how to change the program.|
|2. Feasibility||Deciding on a basic approach for the desired changes, assuming the program will support such changes.|
|1. Requirements||Receiving "orders" for what needs to be changed.|
It should be readily apparent that these steps in producing code lead from one to the next in a natural manner, each line being the foundation or prerequisite for the next. (How much the programmers actually used this model and how much it was a matter of management imposition is still a topic of debate.) Also, in true cyclic fashion, the sixth line ("integration") is the end of one cycle that leads into the next cycle. This corresponds to the observation that software rarely works as requested, and that even if it did, the requirements have probably changed by then. Integration is really only the prelude to the next round of changes, a return to the first line. This accounts, perhaps, for the often pessimistic readings for the sixth line of a hexagram when a moving line appears in that position.
Besides modeling the software development process, the meanings of the lines are often extended to other types of hierarchies or processes (cf. Hx. 7, the Elders). In each of these cases, there is a rough parallel to the six process steps just described, even though these correspondences are often of a fanciful or strained nature. The main point here is that the Wise Ones saw this same process of cyclic changes at work in the world no matter where they looked; in each instance, they expressed it through their archetype of "the process" or "The Six Steps".
In addition to taking the six lines in isolation, the authors of the Q-Ching placed great emphasis on how the hexagram broke up into trigrams. Lines 1 to 3 were termed the "lower trigram" and lines 4 to 6 were the "upper trigram". Since upward motion in the hexagram represents development of the basic cycle of change, the lower trigram was considered the foundation or inner nature of the matter at hand, while the upper trigram was more the outcome or outer manifestation of the same issue. It was very important to have a proper foundation for any undertaking, for the outcome (no matter how auspicious the upper trigram viewed in isolation) vitally depends upon a proper foundation in the beginning. This is nothing more than the earliest recorded version of the infamous computing aphorism "garbage in, garbage out (GIGO)" that seems to have universal applicability.
One of the spin-offs of imagining the hexagram to be composed of lower and upper trigrams is a mapping between lines known as "correspondence". There is a natural affinity of the lines in corresponding positions within the two trigrams, that is, lines 1 and 4, 2 and 5, and 3 and 6 are said to be in correspondence. It was generally considered (although there are numerous exceptions) that corresponding lines were more auspicious or "proper" if they were of opposite parity: a yin and a yang line in correspondence was usually better than two yin or two yang lines. Perhaps this is due to the concept of "I", again, where it is proper for yin and yang to be in perpetual interchange, and an overemphasis on either yin or yang was deemed troublesome or unstable. Further, the lines have a parity relationship with their positions within the hexagram. Since the odd positions (lines 1, 3, 5) are yang, it was better or "proper" to have a yang line in these positions; similarly for yin lines in the even positions (lines 2, 4, 6). These doctrines should not be taken too seriously, however, and definitely are of secondary value in deciphering the hexagrams. For instance, according to these rules, one of the most auspicious hexagrams should be Hx. 9, Infinite Loop, a most decidedly negative reading.
There is also a concept of "rulers" within the hexagram, of lines that symbolize people or roles of special interest in the matter at hand. Usually, but not always, line 5 was considered the ruler of the figure; line 2 (or occasionally line 4) was often considered a helper or "minister" to the ruler. These lines were viewed as particularly important in determining the tone or meaning of the hexagram as a whole, especially when they appear as moving lines. Other than this brief explanation, not much has survived of the original intent of these rulers, and the entire idea is still heatedly debated in the literature.
Similar to the notion that the lines of a trigram refer (bottom to top) to the trinity of powers in the universe of earth-man-heaven, the lines of the hexagram are also divided into three groups of two lines. Lines 1 and 2 refer to earth, 3 and 4 to man, while 5 and 6 point to heaven. Within each pair of lines, the lower one describes the inner, creative aspect (the yang side, since these are odd lines), and the higher one is the outer manifest aspect (yin or even). As noted earlier, there is evidence that this trinity had the esoteric interpretation of hardware-programmer-software as well, although this was definitely an advanced teaching available only to high initiates.
There is some veiled evidence of the notion of "inner trigrams". Not only are the lower and upper trigrams important in interpreting the hexagrams, but the trigrams in the middle are often important as well. Thus the lower trigram consists of lines 1-2-3 and the upper trigram of lines 4-5-6; the inner trigrams contained lines 2-3-4 and 3-4-5. It's as though there was a sliding window of 3 lines width that was moved up the hexagram to different starting points. Several authors have seized upon this fact as evidence of the use of "shift operations" in Chinese computers, as the various trigrams could be isolated or masked off by a combination of logical shifts within the hexagram as a whole. Curiously, there is no mention in the old texts of "wraparound trigrams" (such as lines 5-6-1 or 6-1-2) that could be produced by circular shift operations. Perhaps the Chinese hadn't developed these types of instructions, or maybe this was reserved as a higher, esoteric teaching; the historical data is silent on this point. The absence of a circular shift, particularly in a symbol system designed to represent cyclic change, is a most curious conceptual hole in an otherwise brilliant oracular architecture. At any rate, the various lines fall into 1 to 3 different trigrams, each of which contributes additional commentary to the individual lines. Since lines 1 and 6 belong to only one trigram each, they have a reputation for being weak. Lines 3 and 4, lying in the middle, belong to three trigrams each. The resulting "busyness" of these positions may explain why these lines are also weak, since their influence is scattered in so many directions at once. Lines 2 and 5, in two trigrams each, seem to strike the right balance; this may be why they are not only strong, but usually the "rulers" of the figure. Further analysis of the hexagrams along these lines leads to endless complications and is quite beyond the scope of an introduction such as this.
Finally, it should be noted that many of the hexagram interpretations rely on simple, straightforward pictographic correspondences: the figures simply look like something in the mind of the author. This kind of poetic imagery may seem "primitive" by today's standards, but in the hands of one well versed in the symbolism of the hexagrams and deeply in tune with the Tao, it is a powerful technique not to be slighted.