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Frequently asked questions

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Basic concepts

What is CHARM?
CHARM is an abstract reference model of the cultural heritage. This is a particular kind of conceptual model; specifically, one that is designed to be used by a wide and diverse range of people and extended to meet their particular needs.

What is a conceptual model?
A conceptual model is a formal or semi-formal representation of a subject under study, which can be anything. Being relatively formal, conceptual models are composed of concepts rather than physical parts, and hence the name. Since concepts are abstract and cannot be seen, conceptual models are often visualised in the form of diagrams plus accompanying text. Please see the ConML FAQs for more information.

Why is a conceptual model of cultural heritage necessary?
It is necessary for two main reasons. First of all, a conceptual model helps you understand the portion of reality that you are dealing with much better, since it removes some of detail and complexity that often makes it unmanageable. Secondly, a conceptual model constitutes an excellent language in which to communicate statements about that portion of reality, especially when people from different backgrounds and disciplines are involved.

Ontological and epistemological issues

But cultural heritage cannot be modelled, or not in this way at least.
CHARM is a conceptual model based on the object-oriented paradigm; this, in turn, is highly linguistic. You will see that CHARM represents things in terms of concepts, properties of concepts, and relationships between concepts. This is what human language does through nouns, adjectives and verbs, and through mechanisms such as generalisation/specialisation and classification. You cannot avoid modelling; the mere usage of language to share knowledge and communicate ideas implies a great deal of modelling (albeit non-formal), and a shared understanding of reality. This is what CHARM does.

But a common, shared understanding is not necessarily good; tolerant conflict between incompatible discourses is what makes humanities and social sciences richer.
We do not deny the value of conflict and debate for many purposes in the construction of intersubjective realities. However, there are pragmatic reasons that make a common, shared understanding a valuable resource. The exchange of information between individuals and organisations, especially if they don't share a similar background, is highly facilitated if a common, shared frame of reference is used. Similarly, the existence of a well-known model helps us to reuse knowledge over time, and thus create new knowledge based on the work of others.

Anyway, I don't need a model this large or deep for my particular field of interest.
CHARM is a descriptive, rather than prescriptive, model. You don't need to use everything in CHARM; you can pick only the elements that are useful to you, and refine them to match precisely the needs of your organisation and project, and even your personal preferences. By using CHARM, your information will be readily understandable by others with minimum effort, and will benefit from a model that has been proven to work in a number of situations and conditions.


What is the scope of CHARM?
CHARM represents any thing that may be the recipient of cultural value ascribed by any individual, plus the associated valorisations ascribed to said things, plus the representations of these things that may exist. In this way, CHARM does not only represent the specific entities that might make up cultural heritage, but also other entities which, without doing so, are necessary in order to describe and understand the former.

Will I need to change the way I work in order to use CHARM?
Not much, or nothing at all. Since CHARM is an abstract model, you will need to create a particular model in order to use it. This particular model can reflect the structure and properties of the information that best suit your organisational and project needs, so you shouldn't expect a big adjustment.

What is a particular model?
A particular model is an extension of CHARM that you create in order to use CHARM. CHARM is an abstract model, which describes only so much about cultural heritage. You will need to add the particularities of your organisation, project and situation to CHARM, choosing what information you want to describe and how you want to describe it. The outcome of this process is a particular model.

How do I create a particular model?
You create a particular model by using extension mechanisms on CHARM, which are based on proven object-oriented principles such as specialisation/generalisation of classes and Liskov type compatibility. Extension mechanisms are explained in full detail in the Resources section.


Why is CHARM necessary if there is already CIDOC CRM?
CHARM is necessary because, despite the fact that CIDOC CRM has been available as a standard since 2006, there is no clear and solid approach to create and manage cultural heritage models from an integrative and flexible perspective that is also based on modern modelling techniques and recent advances in software and knowledge engineering.

What are the differences between CHARM and CIDOC CRM?
There are three major differences. First, CIDOC CRM is oriented towards "the curated knowledge of museums", i.e. it focuses on tangible artefacts as understood and managed by museums and similar organisations. CHARM, on the other hand, is much wider in scope, encompassing tangible and intangible entities, agents, valorisations, representations, events and other kinds of things related to cultural heritage with equal emphasis. Secondly, CIDOC CRM is a standard that aims to offer a complete and relatively off-the-shelf solution that is readily applicable. CHARM, conversely, does not provide a finalised, overprescribing solution, but provides only an abstract model that must be extended into particular models to fit each organisation and project. Finally, the formalism (or language) in which CIDOC CRM is expressed has not been explicitly described and is not well documented, which makes processing CIDOC CRM models, or extending the standard itself, a very difficult task. Contrarily, CHARM is expressed in ConML, a well-defined conceptual modelling language that is documented through a public specification, and explicit extension mechanisms are provided so that reasoning and extension on models can be carried out with minimal ambiguity.

Are CHARM and CIDOC CRM compatible?
The answer depend on what we mean by "compatible". From a modelling domain perspective, everything that can be expressed by CIDOC CRM can also be expressed by CHARM; in this sense, they are compatible. However, there are things that can be expressed by CHARM that could not be easily expressed by CIDOC CRM, such as scalar attributes of classes, multivocal (i.e. subjectively varying) values of entities, or much information in domains such as cultural value, rights by agents on cultural heritage, or intangible entities. In this sense, they are not compatible. From a modelling paradigm perspective, CHARM is based on mainstream object-oriented building blocks such as class, attribute and association. CIDOC CRM is roughly object-oriented, but it does not use attributes or associations as generally understood. This means that CHARM and CIDOC CRM are expressed in languages that are similar but different and, therefore, are slightly incompatible.

I am using CIDOC CRM. Should I switch to CHARM?
You should switch to CHARM if the benefits outweigh the costs within a reasonable timeframe. One of the major benefits is the possibility to provide a much better context for your data in terms of the related agents, events, intangible entities, places, valorisations, and other types of entities that CHARM models better than CIDOC CRM. Other benefits include the possibility to describe the subjective and temporal variability of your information, or the advantage of being able to easily extend CHARM to create a particular model that is adjusted to the specific needs of your organisation or project. One last benefit, of course, is that of data compatibility with other CHARM users. Costs, on the other hand, include the cost of learning CHARM, the cost of constructing your particular model, and the cost of data transformation from CIDOC CRM into CHARM.

Technical details

What is ConML?
ConML is a conceptual modelling language that was created for non-experts in information technologies to develop their own conceptual models. It is very easy to use and understand, yet highly expressive, and it has been especially designed with the humanities and social sciences in mind. Please see ConML for more information.

What is a class, an attribute, an association, an enumerated type?
Classes, attributes, associations and enumerated types are the major kinds of elements that make up a model in ConML. They are, so to speak, the "words" in the ConML language. Classes roughly correspond to main concepts (or nouns) in the model, attributes describe properties of those concepts (adjectives or qualifiers), associations describe relationships between conceptos (verbal connectors), and enumerated types correspond to lists of pre-defined options for controlled vocabularies.

Why doesn't CHARM use RDF?
CHARM does not use RDF because RDF lacks abstraction, is too web-oriented, and relies too much on XML. First of all, RDF lacks abstraction, i.e. it focuses too much on the details of how things are implemented rather than the concepts behind them. For example, RDF cannot express in a simple and compact way that an atttribute varies depending on the observer, or that a value exists but is not known. In other words, RDF is geared towards representing data rather than concepts. Secondly, RDF assumes that the web plays a central role on the working of any model. Whereas the web is an important part of information systems today, many models are described and used regardless of the web, and introducing web-centric concepts is an imposing annoyance on the user. Finally, RDF is designed around XML, which is a textual rather than conceptual or visual language. XML is a good option for encoding data, but less than optimal for the representation of complex conceptual models. Having said all this, obtaining an RDF representation of a CHARM model can be trivially accomplished by using encoding tools and conventions.

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