An Introduction to ISO15926 Matthew West

Programme Introduction to 4 Dimensionalism ISO 15926-2 – Lifecycle Integration Schema Introduction to the data model

3D and 4D approaches to ontology In principle, there are infinitely many ways in which we can model the world, so it is perhaps surprising that there are two main approaches, with on the whole minor variations, that dominate the literature.We will call these the 3D paradigm and the 4D paradigm, though they are also known as endurantism, and perdurantism.

4D Ontology A 4D ontology treats all individuals – things that exist in space-time - as spatio-temporal extents, i.e. as 4D objects. The principles of the 4D paradigm are: Individuals exist in a manifold of 4 dimensions, three space and one time. So things in the past and future exist as well as things in the present. The four dimensional extent is viewed from outside time rather than in the present. Individuals (including physical objects) extend in time as well as space and have both temporal parts and spatial parts. When two individuals have the same spatio-temporal extent they are the same thing. (However not all version of 4D insist on this principle). Thus a 4D object is not (usually) wholly present at a point in time, but its whole is extended in space as well as time. The object at a point in time is a temporal part of the whole. Change is naturally expressed through a 4 dimensional classical mereology, which Simons: “Parts: A Study in Ontology” in his seminal work, describes in one page. A good description of, and argument for, the 4D paradigm can be found in Sider: “4 Dimensionalism”.

3D Ontology A 3D ontology treats physical objects (roughly things you can kick) as 3D objects (sometimes called continuants) that pass through time. The principles of the 3D paradigm are: Physical objects are 3-dimensional objects that pass through time and are wholly present at each point in time. Physical objects are viewed from the present. The default is that statements are true now. Physical objects do not have temporal parts. Different physical objects may coincide. The object-at-a-point-in-time is the object of primary interest. To talk about an object at different times it is necessary to time index statements in some way, e.g. X at t. A 3D ontology also has 4D objects in it. These cover activities, such as: a football match - which clearly has temporal parts such as the first half and the second half, a living process - a persons life, rather than the physical person passing through time.

Which paradigm? The 3D approach corresponds well with the way that language works. Language has a focus around here, now, you and me as a context, and on the current state of affairs. This leads to efficient communication under the most common circumstances. On the other hand dealing with change is relatively problematic. Simons requires several chapters to explain how objects change over time in a 3D ontology. What is clear is that the 3D and 4D paradigms cannot be merged into a single canonical approach, since they are contradictory, with one requiring physical objects to have temporal parts, and the other forbidding them. On the other hand, it appears that what can usefully be said using one paradigm can generally be said using the other. We chose the 4D paradigm because we found it to be rigorous, and gave a good account of some difficult cases, like replaceable parts.

ISO15926-2: Integration Model Background Originally the EPISTLE Core Model Started around 1993 Now at Version 4.5.1 As ISO 15926-2 became an International Standard in 2003. http://www.tc184-sc4.org/wg3ndocs/wg3n1328/lifecycle_integration_schema.html

Basic Elements Thing Possible Individual (Spatio-temporal extent) anything, real or abstract Note: the supreme supertype Possible Individual (Spatio-temporal extent) some part(s) of space-time Class collection of things, possibly infinite, where the order is not significant Relationship Something one thing has to do with another.

Space time map A particular spatio temporal extent 3D SPACE TIME

Thing

Possible Worlds Past Future Possible Actual Desired Possible

Possible Individual T > 0 S > 0 3D SPACE TIME

Whole Individual Plastic blank Crushed plastic Cup TIME

point in time period of time T = 0 T > 0 3D SPACE TIME

Possible Individual/State – Temporal whole-part Time period 3D SPACE State Individual TIME

Materialised Physical Object event 1 event 2 3D space B D A C Time

Functional Physical Object/Replaceable Part 3D SPACE installed removed installed removed Tag 101 pump 1 pump 2 TIME

Objects that Overlap John Jennings Chairman of Shell Space Mark Moody-Stuart

Stream connected disconnected valve valve close open tank A 3D space hose tank B Time start filling end filling

Individual

Activity Activity Performer 3D Performer space Input Input Output Time

Event and Point in Time Point in time event 3D SPACE T = 0 TIME

Temporal Boundary point in time event 3D SPACE Sub state TIME

Activity and Temporal Boundary

Some approaches to Set Theory B C 1 2 3 4 5 6 Instances may only be a member of only one set Only one level

Some approaches to Set Theory N X Y Z A B C 1 2 3 4 5 6 Instances may only be a member of only one set Sets hierarchical (model/meta-model etc)

Some approaches to Set Theory N X Y Z A B C 1 2 3 4 5 6 Instances may only be a member of one or more sets Sets hierarchical (model/meta-model etc)

Some approaches to Set Theory N X Y Z A B C 1 2 3 4 5 6 Instances may only be a member of one or more sets Sets not hierarchical (model/meta-model etc)

Some approaches to Set Theory N X Y Z A B C 1 2 3 4 5 6 Instances may only be a member of one or more sets Sets not hierarchical (model/meta-model etc). Loops allowed

Class

Class of Individual

Organisational Levels assembly organism simple artefact molecular atomic sub-atomic “fundamental” particle time

Cup Plastic Hydrocarbon molecules atoms arrangement of arrangement of

Organisational Levels

Information

Information

Information

Summary A 4D ontology sees physical objects as extended in time as well as space ISO 15926 is a data model that is also a 4D ontology It uses a possible worlds approach rather than modal logic Sets are defined by extension

Questions?