Rob brings up a good point in his comment on The Problem of Abstraction in Definitions of Data (http://definitionsinsemantics.blogspot.com/2011/12/problem-of-abstraction-in-definitions.html). He notes that what I am describing is not really abstraction but really a number of different things.
Today it seems the term "abstraction" is used in all kinds of situations when talking about data. For me, it is often difficult to figure out what "abstraction" is supposed to mean in any one of these situations. I strongly suspect that at least sometimes it does not really mean anything. Sometimes I suspect it is even used for marketing hype.
The entry for "abstraction" in Baldwin's Dictionary of Philosophy and Psychology describes how abstraction is filtering out of attributes from an instance or a concept to achieve a particular view of the instance or concept. Rather poetically the entry describes how a child looks at a body of water and becomes fascinated by the lustre caused by the play of sunlight on the surface of the water, to the exclusion of all the other qualities (attibutes) of the water.
This traditional understanding of abstraction as creating a view by filtering out attributes can be used in a special way to create the generalization hierarchies of genus and species (a.k.a. supertype and subtype, or general concept and specific concept). The particular attributes of a group of specific concepts are left behind and attributes that the concepts have in common remain. These are used to form the general concepts that include the specific concepts.
However, abstraction as filtering out of attibutes can generate other perspectives. Abstraction does not always have to lead to the traditional generalization hierarchy. I can understand a man's watch as a timepiece, or a piece of jewelery, or as a fashion accessory.
Now, Rob is right in that I was not using "abstraction" in the above senses. However, I do not have a better term to use for what I was trying to describe. The main idea I was trying to get across is that one concept system can describe or specify another - such as how a data model describes a physical database. The relationship of "description" here is different to every other kind of relationship because the concepts present in the concept system being described have to have some kind of presence in the concept system doing the the describing. This is not the same class of relationship we see in e.g. "I own a car".
So we somehow have the presence of a concept being described (e.g. a column of a physical database table) in a concept system doing the describing (e.g. an attribute of an entity type in a data model).
Rob terms this "representation" (If I understand his comment correctly). This has to be right. However, a representation can often be a picture - a mere image. Technically, this is called a "phantasm" because it does not have the attributes differentiated from the whole. Unfortunately, the process of recognizing and separating the attributes from a phantasm is also called abstraction. It gets more complicated. we cannot take a photograph of a physical database and produce anything like a data model. A database has to be conceieved, not imagined.
Obviously, we are getting into a whole lot of other issues here. I cannot really defend myself against Rob's criticism of my having overloaded (or over-abstracted?) the term "abstraction". However, I do not have a commonly accepted set of terms that I can use to convey the idea of one concept system describing another. More of an excuse than a reason, but it will have to do for now.
Today it seems the term "abstraction" is used in all kinds of situations when talking about data. For me, it is often difficult to figure out what "abstraction" is supposed to mean in any one of these situations. I strongly suspect that at least sometimes it does not really mean anything. Sometimes I suspect it is even used for marketing hype.
The entry for "abstraction" in Baldwin's Dictionary of Philosophy and Psychology describes how abstraction is filtering out of attributes from an instance or a concept to achieve a particular view of the instance or concept. Rather poetically the entry describes how a child looks at a body of water and becomes fascinated by the lustre caused by the play of sunlight on the surface of the water, to the exclusion of all the other qualities (attibutes) of the water.
This traditional understanding of abstraction as creating a view by filtering out attributes can be used in a special way to create the generalization hierarchies of genus and species (a.k.a. supertype and subtype, or general concept and specific concept). The particular attributes of a group of specific concepts are left behind and attributes that the concepts have in common remain. These are used to form the general concepts that include the specific concepts.
However, abstraction as filtering out of attibutes can generate other perspectives. Abstraction does not always have to lead to the traditional generalization hierarchy. I can understand a man's watch as a timepiece, or a piece of jewelery, or as a fashion accessory.
Now, Rob is right in that I was not using "abstraction" in the above senses. However, I do not have a better term to use for what I was trying to describe. The main idea I was trying to get across is that one concept system can describe or specify another - such as how a data model describes a physical database. The relationship of "description" here is different to every other kind of relationship because the concepts present in the concept system being described have to have some kind of presence in the concept system doing the the describing. This is not the same class of relationship we see in e.g. "I own a car".
So we somehow have the presence of a concept being described (e.g. a column of a physical database table) in a concept system doing the describing (e.g. an attribute of an entity type in a data model).
Rob terms this "representation" (If I understand his comment correctly). This has to be right. However, a representation can often be a picture - a mere image. Technically, this is called a "phantasm" because it does not have the attributes differentiated from the whole. Unfortunately, the process of recognizing and separating the attributes from a phantasm is also called abstraction. It gets more complicated. we cannot take a photograph of a physical database and produce anything like a data model. A database has to be conceieved, not imagined.
Obviously, we are getting into a whole lot of other issues here. I cannot really defend myself against Rob's criticism of my having overloaded (or over-abstracted?) the term "abstraction". However, I do not have a commonly accepted set of terms that I can use to convey the idea of one concept system describing another. More of an excuse than a reason, but it will have to do for now.
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