Glossary

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Contents

1. RDF (Resource Description Framework)
   1. Metadata
   2. Data Model
   3. Abstraction
   4. RDF
   5. Subject-Predicate-Object Triple Stores
   6. Uniform Resource Identifier
   7. More Information about RDF
2. RDL ( Resource Description Library)
3. RDS/WIP (Reference Data System / Work In Progress)
4. Conservation of Complexity
   1. Encapsulate
5. AEX (Automating Equipment Information Exchange)
6. Ontology
7. IDS Task 120
8. Some Definitions

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RDF (Resource Description Framework)

If you dig deeper under the hood of ISO 15926 you will soon run into this term because it is the means of storing the Part 4 definitions.

Wikipedia says that Resource Description Framework is a set of specifications originally designed as a metadata data model. But if you are like the author, this doesn't help at all. So we will deconstruct the definition:

Metadata

• Metatdata is data about data. For instance, one piece of metadata about the ISO 15926 Primer is that it was written on the POSC Caesar's wiki website.

Data Model

• A data model is an abstract model that describes how data is represented and accessed.

Abstraction

• Abstraction is a process of generalizing about something to reduce the information content about an object to only those attributes you are interested in. A typical abstraction is the answer "12345-Glover Crescent" to the question "Where do you live?" You might live in a beautiful split level house with a wonderful view of the ocean framed by huge 100 year old pine trees but your questioner only wants to know where to have a package delivered. (On the other hand, yours could be a very ordinary house on a very ordinary road, but the city just wants your land for a freeway bypass and the friendly bulldozer operator needs to know where you live.)

RDF

Putting it all together, then, RDF is:

• instructions on how to represent
• just the bits of data you are interested in
• that describes certain other bits of data
• then access it easily

(Whew! I bet you thought it was going to be difficult!)

In particular, RDF makes statements about things, which it calls Resources, in the form of subject-predicate-object expressions known as Triple Stores.

Subject-Predicate-Object Triple Stores

"The ISO 15926 Primer was written on the POSC/Caesar wiki" might be stored in the RDF as the triple:

• the subject ISO 15926 Primer
• the predicate was written on
• the object POSC/Caesar wiki

The each term in the subject-predicate-object may be explicitly named, as in the example above, or they could be a in the form of a URI, a Uniform Resource Identifier.

Uniform Resource Identifier

You can think of a Uniform Resource Identifier as a website for a piece of information. This allows the same resource to be reliably referenced many times. So instead of writing the Subject-Predicate-Object triple as above, it could be rendered as:

• the subject 'https://trac.posccaesar.org/wiki/ISO15926Primer'
• the predicate was written on
• the object POSC/Caesar wiki

And in fact we could carry this further by defining somewhere on the Internet the exact meaning of the phrase was written on, and put its URI in the predicate.

More Information about RDF

A good place to start if you want to know more about RDF is the RDF Primer written by the W3C. Be warned, it is not for the feint of heart.

http://www.w3.org/TR/REC-rdf-syntax/

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RDL ( Resource Description Library)

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RDS/WIP (Reference Data System / Work In Progress)

The RDS/WIP is several things:

• a library of reference data for ISO 15926
• a means of publishing core ISO 15926 definitions
• a platform for developing new ISO 15926 definitions
• a workspace for harmonizing other standards with ISO 15926 (or each other)

https://trac.posccaesar.org/wiki/RdsWipProject

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Conservation of Complexity

You cannot eliminate complexity. You can move it from one place to another, but it will always be there somewhere. This is used to talk about how we deal with complex Plant information. We can deal with it manually, piece-by-piece, as we have been, or we can encapsulate it with ISO 15926 and let machines deal with it.

This is related to the Law of Conservation of Energy, which says that you can neither create or destroy energy, all you can do is change it from one form to another.

Encapsulate

Hiding complexity from users who really don't want to know any more.

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AEX (Automating Equipment Information Exchange)

The Automating Equipment Information Exchange (AEX) project is developing, demonstrating and deploying eXtensible Markup Language (XML) specifications to automate information exchange for the design, procurement, delivery, operation and maintenance of engineered equipment.

AEX – The natural collaboration between AEX and IDS-ADI is via the Matrix/SIG’s teams.

http://www.fiatech.org/projects/idim/aex.htm

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Ontology

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IDS Task 120

How to use templates

Some Definitions

Semantic versus syntactic	-
Semantic precision	-
Semantic fidelity	-
Reuse	-

We will introduce several new concepts that are fundamental principles of interoperability and integration. They directly relate to the cost of interoperability and integration. Understanding these is the key to reducing cost.

Abstraction	Representing real objects in a general, abstract form
Semantic precision	-
Reuse	-

[Input requested: I'm looking for a good place to talk about these terms. GPR]

Semantic versus syntactic	-
Semantic fidelity	-

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For an extremely detailed Glossary, see STEPDEX: Glossary of Data Management Terms

Glossary of STEP and PDM related terms

Glossary_jun99.doc

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