We are not alone should we dispair at the difficult of expression of concepts.
It is a favourite topic of poets
we have already mentioned H.G.Wells' musing:
There is a sort of stratification in human ideas. I have it very much in mind
that various terms in our reasoning lie, as it were, in different planes, and that
we accomplish a large amount
of error and confusion by reasoning terms together that do not lie or nearly
lie in the same plane.
I would say that there are axes of ambiguity that typically confound our best efforts
The examples in this section illustrate how by use of entity relationship modelling
overcome some of these difficulties.
book(1) and book(2)
It is often the case that a single word in a single dictionary sense can be used
at a number of different levels.
We can illustrate this with the word
book which in its primary sense seems unambiguous but consider how we can ask the question:
How many books were published last year in the UK?
and contrast with our interpretation of:
How many books were sold last year in the UK?
We expect an answer to the first question to be a count of book titles or ISBN numbers
but we expect an answer to
the second to be a count of actual physical books sold by publishers. The use
of the word
book in the first
question is at a different level to the use in the second question. The two are
related and we classify as a reference relationship:
An entity model can help disambiguate these distinct uses.
We have the situation shown in figure
Different uses of
book as a type of entity.
word(1) and word(2)
word itself is also used at different levels. For example if we set
about counting how many words in
the English language we will be counting a different type of entity than if we
count words in an essay or in an advertisement that we pay for by the word.
There is a clear type instance relationship between the two which we again classify
as a reference relationship:
. This thinking leads to the model in figure
The occurrence relation between multiple uses of the word
letter(1) and letter (2)
letter also for we can count the letters in a word and each one is an occurrence of a letter
the alphabet as shown in figure
The scope square of the
occurrence of relationship between multiple uses of the word
word(3) and letter(3)
In the model in figure 53
we introduce a third type of
word and third type of
word (1) - the word as defined by the dictionary. This is the level I am using
when I say
‘What does that word mean?’
word (2) - the words that appear in a book as conceived of by the author. This
is the level I have in mind when I write,
‘In the words of T.S.Elliott’
or, ‘According to the word of God’
. (This last usage of the word
word is given as a
different sense in the
‘Concise Oxford Dictionary’
word (3) - the actual copies of the words in some copy of a book. This is the
level that we use when we say
‘That word is illegible’
Occurrence relationships between multiple uses of the word
This leads to the model shown in figure
This example pieces together the fragments described in the previous sections.
In this model there is a further example of a scope square2; this is shown in figure
A scope square for the occurrence relation between letter(3) and letter(2).
Returning for a moment to the question of when to model a relationship as composition
(vertical) and when as reference (horizontal)
we see that in the model in figure
the distinction between
composition and reference has been representative of these considerations:
alphabet, I describe its letters but I do not describe the
vocabulary of every language using the alphabet.
vocabulary of a language, I describe the words and how they are spelt but I do not describe
corpus of works.
corpus of works, I do not describe the
dissemination of that corpus i.e the printed copies.