www.entitymodelling.org - entity modelling introduced from first principles - relational database design theory and practice - dependent type theory
When a whole is decomposed into parts then very often we find that the part types can be decomposed further. We have seen this already: sentences can be broken down into words and words into letters. These can be shown on a single diagram the relationships are stacked, forming a tower, say, as follows:
The decomposition of wholes into parts can continue over many levels. Thus some linguists, for example, speak of five levels of decomposition of a sentence. These are shown in figure 4. For another example in a dictionary you see each word with its different senses defined and so a dictionary is composed of words and these, within the context of a dictionary, are composed of a number of senses1, see figure 5 for the three levels of a dictionary. Figure 6 shows the parts of an atom as understood circa 1930.