Definition of Entity

Definition Last Updated 17-Dec-2015 12:51

Physical Entity

A physical entity is something deemed to exist and to be identified as a thing by virtue of satisfying a particular specification embodying a description1i.e. a set of observables satisfying given criteria. over an extended spatio-temporal region that, to the limits of the methods of observation, has a closed, orientable boundary2See the technical note on physical extent in the main article.. (See the main article for discussion of the boundary condition.))

The extent of an entity is usually determined by surfaces marking sharp transitions in the values , where the definition of sharpness depends on the precision, resolution, etc. of the observations. The requirement that the bounding surfaces be closed and orientable is what makes entities countable3Thereby justifying the use of the plural..

Entity is synonymous with thing and object but distinguished from stuff. The sea is a thing; sand is stuff. Entities may have parts, i.e. comprise other distinguishable entities; to the limits of the particular observation, stuff does not have parts4October 29, 2015: some stuff, such as sand, might constitute a non-physical entity; I’m not sure yet..

Examples of physical entities include: a (specific) dog, chair, house, personnel record, CPU, magnetic field, etc.

Non-Physical Entity

A non-physical entity5October 29, 2015: the basis for describing non-physical entities is a recent addition to this entry and neither the approach nor the implementation may be as well worked-out as others; the idea that relationships might be non-physical entities seems necessary but may have untoward complications. Feedback is invited via Twitteror the contact page. is something deemed to exist and to be identified as a thing by virtue of the existence of a set of physical entities (i.e. more than one) whose elements’ relationships satisfy a particular specification that describes the elements as having

  • certain relationships in common, or
  • certain relationships between other relationships.

The set of physical entities that satisfy the specification comprise the non-physical entity, i.e. the elements of the set are variously members or parts of the non-physical entity so described.

Note that, thus defined, relationships are also non-physical entities.

Examples of non-physical entities include: a business or enterprise, school of thought, a terrorist cell,

Scope

Entity is a defined term of Enterprise Architecture. Entity is a defined term of Business Analysis.

Discussion

Article Last Updated 17-Dec-2015 12:51

Note that whereas other vocabularies may speak of concrete and abstract things, this vocabulary does not admit abstract things as such, even though abstract would seem to be a good synonym for non-physical. Things typically described as abstract, such as modelling or programming classes are here classified as descriptions6And have implied physicality by virtue of the fact that the descriptions must be manifested in some physical form.. Here to belong to a class, be of a kind, be an instance of, etc. is to satisfy a description.

This approach has the advantage of resolving a common problem in class/instance based architecture modelling: given certain classes, one often creates a pattern of instances7Such a pattern is often called a deployment in MODAF etc. modelling because the pattern reflects the physical deployment of forces and resources. Deploy having the meaning of “to spread out and place (forces) strategically”, from the Latin dis- apart, and plicare to fold., such as a fleet of ships whose component instances are instances of particular classes of ship.

It is then not uncommon to want to re-use such a pattern as a template in a larger pattern, but one is formally then in the position of instantiating instances… unless the first pattern was not in fact made up of instances but of other classes… which would prevent that pattern being used as intended!

The description-thing dichotomy resolves this issue as follows. Patterns of descriptions are themselves just patterns, and only the things themselves are things8I find that I am beginning to sound like a continental philosopher – “Only things are things! Non-things are not nothings but no-things.” – I hope my meaning is, in fact, clear..

If the general idea of the above seems reasonable, the following technical note on the boundaries of physical entities can safely be skipped.

Summary Diagram

The basis for identification of an identity is summarised in Figure 1below.

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

Figure 1 – Asserting an Entity

A Technical Note on Boundaries & Physical Extent

What does it mean for something to have a well-defined (closed and orientable, boundary), i.e. to have a sharply defined physical extent and location – and why is it important to consider this?

The simple answer to the first question is that only a surface that is closed and orientable divides a region in two9A Möbius strip is not closed (it has an edge – even if does only have one of them) or orientable (it has only one side); a Klein bottle is not orientable but it is closed (does not have any edges) so it looks as though it divides space into inside and out but, in fact, does not: two people strolling on (i.e. never passing through) a Klein surface could find themselves standing “on each other’s feet”, i.e. apparently on either side of the surface, thereby demonstrating that there is no “other side”. – the two parts being the inside and the outside. The crossings of boundaries can be counted, and this allows entities to be counted. If things can be counted, they can be given unique identifying names, such as, for want of imagination, “one”, “two”, “three”, etc.

The correct, i.e. unambiguous, identification of the participants in processes etc. is a key aspect of both business analysis and Enterprise Architecture: the descriptions and models created by different practitioners should be coherent with each other and consistent over time so that the representations they comprise can be relied upon with minimal additional work.

Without well-defined entities (and stuff), even attributes – properties (such as power-consumption), behaviours and relationships – cannot themselves be well-defined.

When things are not well-defined, additional effort has to be expended to make otherwise incoherent representations sufficiently coherent in particular contexts that they can be relied on to provide meaningful answers to business and technical questions. This is at best a lot of hard work, and at worst impossible without effectively redoing the whole analysis.

In the sense of well-defined given above, a well-defined boundary ensures that we can reliably identify points as being within or without a surface, which we call typically call the surface of the thing.

Now, the boundary of a three-dimensional object is a two-dimensional surface, but that does not mean that its surface is necessarily in one piece. In fact, the surface can have several pieces: consider the classic, interlocked rings known as Borromean Rings10See Borromean Rings. – as “an object” it has three parts (the individual rings), which are interlocked and the surface of the whole collection therefore also has three parts, but as long as the pieces cannot be separated without passing through each other, we would tend to call the whole one thing because the parts cannot be moved around completely independently of each other.

Unfortunately, this means that no local measurements of physical properties can determine whether we are dealing with one or more than one object: the interlocking of things such as Borromean rings can only be determined topologically (via the theory of knots11See Knot Theory.).

Finding the Boundary

As to how a boundary may be identified, consider the measurement of density along a line passing through a brick and extending some way to either side. Assume it is a brick in air or a vacuum, whose densities are very low compared to that of brick (the stuff), as shown below.

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Figure 1 – The Density Profile of a Brick

As measurement proceeds along the line, the measurement volume begins to impinge on the substance of the brick and the density begins to increase. The derivative of density along the line changes from zero to positive. Assume that the measurement volume is smaller than the nominal thickness of the brick along the measurement line; as the measurement volume traverses the interior of the brick, the density is constant, i.e. the derivative of density is again zero. Noting that it was previously positive, it must have decreased again.

Likewise, on emerging from the other side of the brick the density decreases, the derivative is initially negative and remains so until the measurement volume has completely exited the brick, at which point it returns to zero again.

One may use any observable as the basis for determining a boundary.

There is, however, a problem in that the boundary must be continuous if it is to divide inside from out and the only way that continuity can be determined is to examine all lines passing through the region of interest.

For technical reasons, if we are not to miss any entity boundary within the observation region, we should define a closed region of observation and ensure that all lines of observation pass through a single point within the observation region, and – if we allow some uncertainty in our observations, and imagine not lines but cylinders of observation – require that the collection of cylinders of observation cover the boundary surface of the region of observation.

With observations arranged thus, it becomes impossible to miss something within the observation region, and although, given the uncertainty of observations, it remains possible that multiple entities appear to be a single entity, we can at least be sure there is at least one thing there.

Notes   [ + ]

1.i.e. a set of observables satisfying given criteria.
2.See the technical note on physical extent in the main article.
3.Thereby justifying the use of the plural.
4.October 29, 2015: some stuff, such as sand, might constitute a non-physical entity; I’m not sure yet.
5.October 29, 2015: the basis for describing non-physical entities is a recent addition to this entry and neither the approach nor the implementation may be as well worked-out as others; the idea that relationships might be non-physical entities seems necessary but may have untoward complications. Feedback is invited via Twitteror the contact page.
6.And have implied physicality by virtue of the fact that the descriptions must be manifested in some physical form.
7.Such a pattern is often called a deployment in MODAF etc. modelling because the pattern reflects the physical deployment of forces and resources. Deploy having the meaning of “to spread out and place (forces) strategically”, from the Latin dis- apart, and plicare to fold.
8.I find that I am beginning to sound like a continental philosopher – “Only things are things! Non-things are not nothings but no-things.” – I hope my meaning is, in fact, clear.
9.A Möbius strip is not closed (it has an edge – even if does only have one of them) or orientable (it has only one side); a Klein bottle is not orientable but it is closed (does not have any edges) so it looks as though it divides space into inside and out but, in fact, does not: two people strolling on (i.e. never passing through) a Klein surface could find themselves standing “on each other’s feet”, i.e. apparently on either side of the surface, thereby demonstrating that there is no “other side”.
10.See Borromean Rings.
11.See Knot Theory.

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