A Museum Mapping for the Real World

The BM Mapping in a Nutshell

The contextual generalisations of the Conceptual Reference Model (CRM) have been derived by examining a wide range of data models particularly from the cultural heritage and museums sector. This means that many of the concepts are familiar to those working with museum documentation. The following provides a summary of the mapping for a typical British Museum object based on some key CRM properties (it is not comprehensive and does not describe all elements). As you will see the CRM closely follows the events and concepts that many museum staff find familiar and uses real world descriptions rather than the technical labels commonly found in databases tables. The CRM differentiates itself from other aggregating frameworks because it does not attempt to strip down data sources into a common set of fields but instead provides a model for harmonising rich and complex data sets, from whatever source and however formed, to derive the maximum benefit.

The CRM requires an understanding of the domain and range of the properties that it uses. Every CRM property has a carefully selected scope of use. It will only be applicable for a specified domain (the subject of an RDF triple) and a specified range (the object of a triple). The CRM has a structure of classes and the while the domain and range are specified at the highest appropriate class its sub-classes are also implied. Therefore the range of E39_Actor includes the sub-classes E21_Person and E74_Group. A domain of E5_Event includes the sub-class E7_Activity and its sub-class E8_Acquisition – and so on.

The following summary is not an instruction in mapping CRM but an exercise in demonstrating the appropriateness of the ontology to cultural heritage objects. The narrative underlines terms that are reflected in the labels of properties and classes that are listed (again not comprehensively or in any order) next to the narratives. The summary is taken from a larger document that does describe the mapping process in more detail.

Narrative Properties Classes
Museums hold objects that tell the history of the world. These objects sometimes have a title and are recorded with an identifier (an accession number). Some objects form part of a sub-collection with a collection title.
  • P102_has_title
  • P1_is_identified_by
  • P46i_forms_part_of
  • E22_Man-Made_Object
  • E35_Title
  • E42_Identifier
  • E78_Collection
CRM Mapping NoteThe domain of the property P102_has_title is E71_Man-Made_Thing.  A BM object is typed as an E22_Man-Made_Object which is part of the E71_Man-Made_Thing class hierarchy. Therefore P102_has_title can be used with a man-made object. The range is E35_Title. Therefore the node that the triple uses as an object node (as in subject – predicate – object) must be of type, E35_Title.The domain of P1_is_identified_by is E1_CRM_Entity (so any entity in the CRM could have an identifier. The range is E41_Appellation. E41_Appellation has sub-classes that include E42_Identifier. Therefore to make the triple using P1_is_identified_by valid the object node in the triple is, and is typed as, an E42_Identifier.Lastly, P46i_forms_part_of is the inverse of the property P46_is_composed_of, and is used to show that the object forms part of a collection. It has a domain and a range of E18_Physical_Thing. This class includes the sub-class E24_Physical_Made-Made_thing which in turn has the sub-class E78_Collection. Therefore a collection is a type of E18_Physical_Thing and is valid for the mapping.
Most collection catalogue databases will allow curators to write some comments or notes about the object.
  • P3_has_note
  • E62_String
CRM Mapping NoteAs you might expect P3_has_note has the domain of E1_CRM_Entity and can therefore apply to any triple subject (you can write notes about anything). Its range is E62_String and therefore the node it points to must be of type E62_String. Straight forward, yes?(Note: You may be starting to understand how the CRM ensures integrity of mapping. This is essential for the end product to make sense, but also ensures data harmonisation.
Museums will record where the object came from and therefore the details of the various transfers of it from one person or organisation to another, and ultimately to the current owner. However, the current owner could be a third party if the object is on loan, and the acquisition may simply be a transfer of custody rather than of ownership.
  • P23_transferred_title_from
  • P51_has_former_or current owner.
  • P52_has_current_owner
  • P28_custody_surrendered_by
  • E22_Man_Made_object
  • E8_Acquisition
  • E10_Transfer of Custody
CRM Mapping NoteP23_transferred_title_from is a predicate that uses a subject node with a type of E8_Acquisition (domain) but must refer (range) to an E39_Actor (e.g. a person E21 or a Group E78). This makes sense because the object must come from some sort of group or person. For P51_has_former_owner we are talking about the object’s (E22_Man-Made_Object) former owner (the domain is E18_Physical_Thing) and a range of E39_Actor again (Acquisitions work around people or organisations). Likewise the property P52_has_current_owner also operates in the domain of the physical thing (E18_Physical_Thing) and the range of an Actor.P28_custody_surrendered_by has a range of E39_Actor but the domain is E10_Transfer_of _Custody. This triple operates between the acquisition node (typed as a transfer of custody as well as an acquisition) and the actor from which the object was transferred. Other forms of transfer exist likeP24_transferred_ownership_through (rather than ‘from’). The semantics are different and therefore there will be different forms of acquisition mapping. We call this different constructs
In some cases details of where an object was originally found are known and recorded.  The find itself is an event at which the object was present.
  • P12i_was_present_at
  • EX_Discovery (BM specialisation)
CRM Mapping NoteP12i_was_present_at is the inverse of the property P12_occurred_in_the_presence_of which is used in the domain of E5_Event. The Museum has created a sub-class of E5_Event called EX_Discovery to describe the event of discovery of an object. If the CRM doesn’t have a class that describes your entity fully then you can usually create a sub-class of an existing CRM class. The BM has limited the number of class specialisations to the absolute minimum and instead made use of typing by vocabularies.
Further investigation of the object will often provide more information about how the object was created or produced in the first place. Like an acquisition or a find, a production is an event with a range of useful information. For example, the technique used to produce the object. The BM records the broad production types to support precise searching.
  • P108i_was_produced_by
  • P32_used_general_technique
  • E12_Production
  • E55_Type
CRM Mapping NoteP108i_was_produced_by provides the initial relationship between the collection item and the production event node. Therefore the domain must be the classes that describe an object, in this case E24_Physical_Man-Made_Thing which clearly denotes that this is an artificial thing that has been produced (and encompasses E22_Man_Made_object).P32_used_general_technique works with activities (E7_Activity being the domain) and production is indeed an activity because it is a sub-class of E11_Modification which is, in turn, a sub-class of E7_Activity. The British Museum then uses a thesaurus of technique terms in a SKOS format – the term itself is typed as E55_Type – which is the range of P32_used_general_technique.
The period in which production falls within is a key piece of information and may be accompanied by a date or specific time period.
  • P10_falls_within
  • P4_has_time_span
  • E52_Time_Span
CRM Mapping NoteP10_falls_within has both a domain and a range of E4_Period.  An example of a period is an E7_Event and all activities are therefore within the sub-classes of E4_Period, including say, an E8_Acquisition. Therefore in the mapping we can use P10_falls_within with any event object but must ensure that the triple subject comes within the realms of E4_Period node before defining the details of the period. This is done by creating an appropriate date URI, typed as a time span, to hold the date information.
People and places are commonly associated with production information. The people, groups or artistic schools who carried out the production of the object and the locations where production took place (which might be various) are important material aspects of the object.
  • P14_carried_out_by
  • P7_took_place_at
  • E21_Person
  • E39_Actor
  • E74_Group
  • E53_Place
CRM Mapping Note The most frequent use of the generalisation P14_carried_out_by in the Museum’s mapping is in production, and in particular, the relationship with people and places (using P7_took_place_at).Unsurprisingly P14_carried_out_by has a domain of E7_Activity (as production is also an event) and a range of E39_Actor.  P7 P14_carried_out_by has the same domain but the range is, of course, E53_Place.
Other people indirectly involved in the process might be those who influenced the production (another artist for example) or were the motivation for it, like a coin minted for an emperor. Otherwise an object might have been made for an event.
  • P15_was_influenced_by
  • P17_was_motivated_by
  • E21_Person
  • E39_Actor
  • E74_Group
  • E53_Place
  • E5_Event
CRM Mapping NoteP15_was_influenced_by and P17_was_motivated_by are again talking about the domain of ‘activities’. In the BM mapping these might be people or groups who have influenced or motivated (although P15 and P17 have a range which includes all CRM entities (E1_CRM_Entity) a production process. These are generalisations that are very open to reification with internal vocabularies. For example, the motivation of something through an authority, like an emperor, is useful information to add to the mapping.
If the object has an inscription on it then this is a type of visual item which might directly refer to a subject, place, person or group.
  • P65_shows_visual_item
  • P67_refers
  • E65_Creation
  • E34_Inscription
CRM Mapping NoteP65_shows_visual_item refers to  E24_Physical_Man-Made_Thing and has a range of E36_Visual_Item. In the mapping this is a node created for the purpose of using P67_refers (which has the domain of E89_Propositional_Object – a class containing immaterial objects like information objects (E73_Information_Object). An Information object includes a visual item (E36_Visual_Item) that itself contains a class for ‘markings’ (E37_Mark) and this has the sub-class for inscriptions (E34_Inscription) – and therefore is a valid range for P65_shows_visual_item.
An inscription is a type of production process (a creation) in its own right and therefore we may record specific production information against it including the person who carried out the inscription (who may be different from the object producer).
  • P14_carried_out_by
  • E21_Person
CRM Mapping NoteSee production above
The object may directly depict or visually represent as an image place, person or group and so on.
  • P62_depicts
  • P65_shows_visual_item
  • P138_represents
  • E38_Image
  • E21_Person
  • E39_Actor
  • E53_Place
CRM Mapping NoteDepiction is a short cut for a visual image (picture) representation. P65_shows_visual_item can refer to a picture (image) on the object itself (the domain and range above). Instead of P67_refers a pictorial representation uses the property P138_represents. This operates with a (you guessed it) an E36_Visual_Item and any other CRM entity (E1_CRM_Entity).
The object may also have more indirect associations to these things and carry references. The object may also have conceptual subjects (information object) which can tell people more about the object and its meaning.
  • P128_carries P67_refers
  • P129_is_about
  • E73_Information_Object
CRM Mapping NoteAn object may refer to something in a more indirect conceptual way. The Museum has invented a URI node called ‘concept’ and typed it as an E73_Information_Object. P128_carries can use this node as its range (with a domain of E24_Physical_Man-Made_thing – the physical object) and this provides the basis for a reference to an E21_Actor (like an ethnic group – e.g. this visual design alludes to a particular culture)  or an recorded event. P67_refers has the domain E89_Propositional_Object (including an E28_Conceptual_Object) and can have a range of any concept.  P128 has the range E90_Symbolic_Object (including the “aggregation of symbols”) covering subject terms.
Other more technical information is also recorded against the object like the material it was made out of (or that it consists of).
  • P45_consists_of
  • E57_Material
CRM Mapping NoteThis one is straight forward. P45_consists_of has a domain and refers to an E19_Physical_Thing and has the range of E57_Material. This would be a thesauri identifier leading to a SKOS schema for the term.
Dimension measurements are taken for the object and these are stored as values and units.
  • P43_has_dimensionP90_has_value
  • P91_has_unit
  • E54_Dimension
CRM Mapping NoteP43_has_dimension operates over E70_Thing (our object again) and has the range of an E54_Dimension. E54 provides the domain for P90_has_value which has the range of E60_Number.   P91_has_unit has the same domain but the range E58_Measurement.
Objects will be documented in bibliographic material which is created through publishing and authoring. This includes journals (a component of a series) and references that are part (components) of a collection.
  • P70i_is_documented_in
  • P94i_was_created_by
  • P148i_is_a_component_of
  • E31_Document
  • EX_Bibliographic _Series
  • E65_Creation
CRM Mapping NoteNot surprisingly P70_documents (P70i _ is_documented_in) refers to E31_Document and can apply to any CRM entity. P94_has_created has the domain E65_Creation and applies to E28_Conceptual_Object. In this case the concept is ‘Authoring’. P148i refers to a document being part of a E89_Propositional_Object
People might be identified with different names (or appellations) and the Museum records people who belong to or were members of a school (of art for example). These are people of different (belong to) national groups.
  • P131_is_identified_by
  • P107i_is_current_or_former_member_of
  • E39_Actor
  • E21_Person
  • E74_Group
CRM Mapping NoteP131 is used specifically to identify the name of an E39_Actor with the range E82_Actor_Appellation. P107 deals with members of a group with the domain being E74_Group and a range of E39_Actor.