Best Practices

Showing 9 results:

Implementing the CIDOC Conceptual Reference Model in RDF

Answer:

Reference links:

http://www.cidoc-crm.org/Resources/implementing-the-cidoc-conceptual-reference-m…

Reference to Cidoc Version:

version 7.0.1

Post date:

2020-10-23

Authors:

Martin Doerr;Richard Light;Gerald Hiebel

Implementing properties of properties (.1) by using has note (P3)

Title:

Adding notes for most specific interpretation of properties

Answer:

Frequently scholars and scientists would like to express more detail about a particular relation (property) between two entities than the type of the property itself expresses. These may be more details about the respective role or attitudes or arguments about the reliability of the information. In order to formally attach notes to properties in the currently dominant knowledge representation languages, one needs to replace the property by an equivalent path with an intermediate, auxiliary entity. Even though this mechanism has been provided for the CRM as "property classes", depending on the implementation choices, this may increase the complexity of the model and the user interface and decrease the performance of respective databases. The details given are in most cases not relevant in order to filter a large set of data by it. In that case they are relevant for the receiving user, but not for querying, and hence can be better expressed in a textual note.

The question that arises is where to put the note, if not to an intermediate entity: to the domain instance or the range instance of the respective property. This is often intuitively done in the opposite way it should be done.

For instance: "Building house X"(E12) - P4 was carried out by - "John Smith"(E21)- P3 has note: "in the role of designer" sound perfectly logical, but is wrong!

This is the effect of context-free propositions in KR. The user sees the local context, but the note is attached to the person, not to the building activity. The role however does not hold for the person at all times, but only for this person in this activity. If "John Smith" will have another role in another activity, the context of this role becomes ambiguous. Therefore, if a note is meant to describe a property, but is instead attached to either domain or range instance, it must contain, in textual form, the path to the other entity instance.

This leaves two choices for the above example:

A)"Building house X"(E12) - P4 was carried out by - "John Smith"(E21).

"Building house X"(E12) - P3 has note: "was carried out by John Smith in the role of designer"

B)"Building house X"(E12) - P4 was carried out by - "John Smith"(E21) P3 has note: "performed Building house X in the role of designer"

Of these two options, A is the recommended solution. The instance "Building house X"(E12) is actually the context for this role, or, in other terms, more specific to the property instance than the actor. The rule, therefore, is to attach the note about a property to the domain or range instance that provides the context to describing the property, as shown in choice A) in the above example, if the property is not going to be expanded by an intermediate entity. Otherwise, one has to repeat the missing path in the note as shown in B), above, which is suboptimal.

Another solution for implementing .1 properties in RDF is documented here

Reference to Cidoc Version:

version 6.2.6

Post date:

2019-10-15

Authors:

crm-sig

P165 incorporates (is incorporated in) and digitazation

Title:

This is a guideline about the conditions it can be said that a digitization of a physical object incorporates an information object that the physical object that was digitized carries.

Answer:

An important class of E90 Symbolic Objects consists of arrangements of instances of a finite set of symbols, such as the character types of an alphabet, following rules of arrangement that make the relative order of the symbols unambiguous, such as writing symbols regularly spaced, in regularly spaced lines, aggregated into paragraphs etc. Most texts, but also diagrams such as metro maps fall under this category, because they represent stations and their connections in a way only loosely related to their actual geometry. The rules for the arrangements of symbols quantify relative positions so that they can unambiguously be interpreted as logical structures or grammars. For instance, inter-word spaces are sufficiently larger than inter-character spaces not to confuse them. We denote these objects as “formal symbol structures”. Common to them is the property that there is a minimal resolution under which they are still “readable”, i.e. under which the used kinds of symbols can be distinguished and the logical role of their relative positions unambiguously be interpreted. This even holds for melodies expressed in some musical key. If the digitization of a physical carrier of such a formal symbol structure is carried out in the necessary resolution and coverage, the complete symbolic content of the physical carrier will also be readable in a representation of the reproducing digital object, as well known from operating paper scanners. Then, the digital object will incorporate (P165 incorporates) the symbolic object on the physical carrier.
Ambiguity about this property may, for instance, arise if some characters are badly readable on the original. For practical reasons, we recommend not to regard such minor shortcomings of the original as a reason to question the P165 incorporates relation of the digital representation, as long as the overall sense (or score) is recognizable, in particular, if the intended meaning can be guessed equally well from the original as from the digital representation. The same holds for minor flaws in the digital representation itself.
In contrast, for symbolic objects in a non-discrete form, such as paintings, there is no clear minimal resolution and the actual color reflection behavior cannot be reproduced digitally with current means. As long as this is the case, the digitized image cannot be said to incorporate the original, it only “P138 represents” it. (For audio recordings, there is no equivalent to P138 represents, and the more general P67 refers to should be employed). Actually, the symbolic object a physical object carries is not uniquely defined by the physical carrier but depends on the type of the symbolic object defined in a model, which in turn serves a purpose of representation. If, for instance, the original is a manuscript, a digitized image may incorporate its text, which is instantiated and defined as a symbolic object of type “character sequence” in an information system. However other research-relevant optical features, which belong to richer symbolic properties of the manuscript surface, such as colors, may not be resolved by the image. This richer definition of a symbolic object carried by the physical object would not be incorporated in the digitized image. In other words, the type of the symbolic object that is described to be carried by the physical object determines the features under consideration and hence allows for deciding if the digitized image has sufficient qualities to incorporate it. At the time of writing there is still no good typology of symbolic objects with respect to the relevant representational feature types.

Post date:

2017-10-05

Authors:

Martin Doerr, Øyvind Eide

Modelling States of Prints using FRBRoo

Title:

How to model prints (visual works) with FRBRoo / CRM?

Answer:

Definition of Print (visual works) from the Art and Architecture Thesaurus (AAT): “Pictorial works produced by transferring images by means of a matrix such as a plate, block, or screen, using any of various printing processes.” Thus a print is a visual work, created through a wide range of techniques that involve making an ink impression on paper or other material (etc.) based on a matrix or plate which creates the image. Many techniques for preparing the matrix or plates and striking the prints exist.

The plates are usually intended to be used multiple times to produce multiple, essentially identical, copies of the print. This fits with the definition of an industrial process. In FRBRoo this concept applies to any system of production that can create objects in a series, including small-scale production processes; it is not restricted to large factory production.

In the simple case, the modelling of prints using FRBRoo is exactly parallel to the creation of any other F3 Manifestation Product Type:

F32 Carrier Production Event R26 produced things of type F3 Manifestation Product Type.

The use of a specific plate (E24 Physical Man-Made Thing) can be modelled with the addition of P16 used specific object. The creator is modelled with an E39 Actor linked to the F27 Work Conception and to the F28 Expression Creation, producing an F22 Self-contained Expression, and possibly a different E39 Actor linked to the actual printing via F32 Carrier Production Event R28 produced F54 Utilized Information Carrier. The individual prints are instances of F5 Item.

At various stages during the production of the matrix or plate, prints (proofs) may be taken by the printmaker to ascertain the evolution of the image. (This is because it can be difficult to gauge the printed result merely from viewing the matrix.) In the course of the print run, or prior to starting a new print run which reuses the same physical plate, alterations may be deliberately introduced, either by the original creator or by someone else, on the plate (adding details or modifying part of the image) which produces variants or states of the print. Each proof, or set of proofs, documenting an intentional alteration of the matrix or plate defines a distinct state. This is a deliberate process, not merely the normal wear of the plate through repeated use (which might result in later copies being less crisp, for instance, than those produced at the beginning of the print run).

In the Descriptive Cataloging of Rare Materials (Graphic materials) (DCRM(G)), a “state” is defined as follows:

“In graphic usage, an impression or set of identical impressions produced from a plate or other matrix at a distinct, visually identifiable stage in the life of that matrix due to intentional changes to the matrix, and often marking a point in its artistic development (such as “etched state” or a “state after letters”).”

In FRBRoo the process of creating a state can be modelled using an E39 Actor linked to E81 Transformation P124 transformed E24 Physical Man-Made Thing (subclass of E77 Persistent Item) (the plate). The instance of E39 Actor may or may not be the same as the one responsible for the original work creation, etc. This transformation event happened at a given time, then the production of F3 Manifestation Product Type after this time is a new instance of F3, so the F5 Items produced using the modified plate are items of this later manifestation, which embodies a new expression of the F1 Work, derived from the previous F22 Self-contained expression.

This is analogous to the situation of the production of books by hand-press printing. Once the type was composed and the printing process started, states within that impression could be obtained when more or less minor changes were made to the type in the course of printing. Some of these variations can be significant and result in variant manifestations, or even variant expressions.

(For more details on states of early printed books see: Jonsson, Gunilla. Cataloguing of hand press materials and the concept of Expression in FRBR. In: Functional Requirements for Bibliographic Records (FRBR) : hype or cure-all? Patrick Le Boeuf (editor). Haworth Information Press, 2005, pp.77-86).

Post date:

2017-01-12

Authors:

Pat Riva

What is Color ?

Title:

What are the physical parameters that the colour depends on?

Answer:

Colour is a property which can be defined in the sense of physics or in the sense of human neurophysiology. The way humans perceive colors is complicated, but scientifically well understood.

Color of a surface in the sense of physics is the spectrum of light frequencies emitted from a surface. Neglecting active light sources, it is a reaction on the frequencies of the incoming light, and therefore depends on it. Out of physiological reasons, standard colors are defined with respect to a standard light source that represents an ideal daylight. Such devices are used in labs. The standard daylight source has a continuous spectrum of a known shape.

The human eye registers, i.e., projects out of the reflected spectrum three sub-spectra, one centering at red, one at green, and one at blue. The combination of the intensities of these three components produces our sensory impressions of all colors, including violet and yellow. These effects can be reproduced by adequate mechanical sensors and processing.

The surface itself may have unlimited details, microscopic differences in reflection. The reflected light is always the sum of the light reflected from some surface of a certain size. Therefore color is only defined with respect to a certain spot size. Seeing a surface from a certain distance increases the spot size, and hence may produce new integral colors, as well known from a TV screen surface. Also quick change of light ( >25 cps) sums up to an integral sensory reaction.

In addition, our brain has two extraordinary processing functions, which keep our color impression much more constant than physics would make us expect:

A) White balance: Standard daylight is “white”. Our brain detects deviations of the light source from being white, and corrects the sensory impression very widely in order to produce correct colors as if the source were white. Digital cameras try more or less successfully to simulate this process as “automatic white balance”.

B) Surface homogeneity: Our brain mysteriously detects shadows and colored reflections on homogeneously colored surfaces and presents itself the corrected surface color. So we recognize for instance a pullover to be uniformly red within complex light conditions, reducing the surface color to the woolen thread color.

Consequently, describing “the colour” of an object is not a question of a simple vocabulary. Even given under standard light conditions, it still needs the definition of the spot size of integration, and the representative surface parts of features meant by this categorization.

Art conservators recently tend to scan art objects by much more colors than the three colored subspectra the human eye distinguishes. This allows for much better print representation and scientific analysis of colorants.

Post date:

2016-03-01

Authors:

Martin Doerr

Headers of the Erlagen version of OWL of CIDOC CRM

Title:

What are the approved by CRM- SIG headers for Erlagen OWL implementation of Official CIDOC CRM

Answer:

Official CIDOC CRM / Erlangen CRM OWL Header (SIG approved, no restrictions etc.)

Version DDMMYYYY of the Erlangen CRM

- implements CIDOC CRM Version 5.0.5

- uses OWL Version 1.0 DL

Things you should know about before use

- the CIDOC Conceptual Reference Model (CIDOC CRM, http://www.cidoc-crm.org/)

- the Web Ontology Language (OWL, http://www.w3.org/standards/techs/owl)

- the primer for the Web Ontology Language (https://www.w3.org/TR/owl-primer/)

- the Erlangen CRM (ECRM, http://erlangen-crm.org/)

This Version of the Erlangen CRM

- is the recommended OWL implementation of the CRM approved by the of the CIDOC CRM Special Interest Group (SIG)

- contains all classes, properties, scope notes and examples of the CIDOC CRM

- contains class and property hierarchy as well as statements for transitive and inverse/symmetric properties

- does not contain any further restrictions or quantifications

In case this is not the version you were looking for, consider using

- the standard Erlangen CRM (http://erlangen-crm.org/current-version)

- the RDF version as provided by the CRM SIG (http://cidoc-crm.org/official_release_cidoc.html)

- the standard document of the CIDOC CRM (http://cidoc-crm.org/official_release_cidoc.html)

Standard Erlangen CRM OWL Header

Version 150929 of the Erlangen CRM

- implements CIDOC CRM Version 6.2

- uses OWL Version 1.0 DL

Things you should know about before use

- the CIDOC Conceptual Reference Model (CIDOC CRM, http://www.cidoc-crm.org/)

- the Web Ontology Language (OWL, http://www.w3.org/standards/techs/owl)

- the primer for the Web Ontology Language (https://www.w3.org/TR/owl-primer/)

- the Erlangen CRM (ECRM, http://erlangen-crm.org/)

This version of the Erlangen CRM

- is NOT the recommended OWL version of the CIDOC CRM Special Interest Group (SIG). See http://erlangen-crm.org/current-version for the recommended OWL version.

- contains all classes, properties, scope notes and examples of the according CIDOC CRM version.

- contains class and property hierarchy as well as statements for transitive and inverse/symmetric properties

- contains existential and quantitive property restrictions derived from the CRM scope notes and quantifications

- supports automatic deduction systems to find logical contradictions

- may be used by people knowing restrictions as well as their benefits and drawbacks or for those who are convinced the ECRM developers know what they are doing

In case this is not the version you were looking for, consider using

- the SIG-recommended Erlangen CRM ‘without restrictions’ (http://cidoc-crm.org/something)

- the RDF version as provided by the CRM SIG (http://cidoc-crm.org/official_release_cidoc.html)

- the standard document of the CIDOC CRM (http://cidoc-crm.org/official_release_cidoc.html)

Post date:

2016-02-26

Authors:

Mark Fichtner

Erlangen CRM / OWL

Title:

The name spaces for the enconding of CIDOC CRM in RDF & OWL

Answer:

Versioning Mechanism

http://www.cidoc-crm.org/cidoc-crm/ and http://erlangen-crm.org/current/ follow the same mechanism already

Versioned namespace (e.g. http://erlangen-crm.org/150716/) is mainly for users who want to be able to track which version of the document they used at a certain point in time (e.g. in order to track how concepts were described in old versions)

There is no such mechanism for the rdf

Suggestion: Synchronisation via equivalence on the ontological layer for the two above

Post date:

2016-02-02

Authors:

Christos Georgis, Mark Fichtner

Roles in the CIDOC‐CRM / modelling properties of properties

Title:

How to model Roles in the CIDOC‐CRM RDF encoding / How to model properties of properties

Answer:

This is a presentation about how to model Roles in the CIDOC‐CRM RDF encoding.

This is a proposal of enconding Roles in rdfs

Reference links:

modelling Properties of Properties (last update 2/8/2016)

Post date:

2015-02-12

Authors:

Martin Doerr

Allen Operators

Title:

A brief explanation of time

Answer:

You may find here a brief explanation of time

Post date:

2007-07-12

Authors:

Matthew Stiff

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Best Practices

Adding notes for most specific interpretation of properties

Official CIDOC CRM / Erlangen CRM OWL Header (SIG approved, no restrictions etc.)

You may find here a brief explanation of time