Introduction to the CB-NL

Background

In 2012, the BIR decided to start the development of the CB-NL: the Dutch concept library. This decision was based on the pilot phase in which the need and objective, but also the configuration, requirements and workplan for the CB-NL were determined. This was reported in the document “Nederlandse conceptenbibliotheek (CB-NL) Hoofdrapportage Pilotfase”.

The Modeling Guide is an elaboration of the modeling principles as described in the report of the pilot phase. Since then it has been updated based on new insights from the work being done to fill the CB-NL with concepts.

The Nederlandse Conceptenbibliotheek (CB-NL) is a library or collection of concepts for the building knowledge domain. This library is in fact an ontology, which defines concepts and semantic relations between these concepts.

The starting point for CB-NL is OWL2. CB-NL conforms with ISO 12006-3 and ISO 16354.

One aspect of the CB-NL ontology is its application as a regular controlled vocabulary: it contains terms and definitions in Dutch and English that users of the CB-NL agree to use. These terms function as labels or symbols for the concepts in the library. But this is only a part of the ontology. It also contains a taxonomy: the concepts are structured in a hierarchy. In this taxonomy concepts can be a subclass of more than one concept. The ontology also contains non-hierarchical relations between concepts, making it possible to capture all kinds of knowledge about the world.

The terms vocabulary and ontology are often confused and/or used to mean the same or similar things. Usually, the term controlled vocabulary is used for simple, usually informal collections of terms, while the term ontology is most often used when referring to more complex and formal (i.e. with a strictly applied structure) collections of terms and their interrelations (see W3C Vocabularies).

In this document, we use the terms to mean distinct things. The controlled vocabulary is seen as the simplest form of a collection of terms, to which a dictionary, taxonomy and ontology each  add a layer of information and complexity.

A vocabulary is a collection of terms  [ISO 16354] that users from a domain agree to use, or in other words, a set of domain-dependent predicates and functions that provide the basis for the statement of facts [Brachman et al 2004, p32, 209].: all the things that play a role in some domain, are named in the vocabulary. A vocabulary is just that: a list of names (labels) of things. Part of the CB-NL ontology is a vocabulary. The vocabulary contains terms in Dutch and/or English. 

A dictionary enriches the terms from a vocabulary with descriptions of their meanings.

A taxonomy is an ordering of concepts in a tree-like structure. The concepts have a name (vocabulary) and meaning (dictionary). A taxonomy is organized hierarchically, with the most general concepts at the top and the more specialized ones further down; a specialization hierarchy of classes. [Brachman et al 2004, p172]. The top concepts of the hierarchy are predefined in CB-NL and described later on in this guideline (see Top-level CB-NL).

An ontology, as the term is used in the field of Knowledge Representation, is a catalogue of the kinds of objects (constants, functions, relations) that are important in a domain (i.e. a sphere of knowledge, influence, or activity – Merriam Webster dictionary), the properties those objects will be thought to have, and the relationships among them. The kinds of objects in an ontology are also called concepts. The relationships in an ontology are not necessarily hierarchic. In CB-NL, relationships between concepts such as behaviour (function) are used for their definition.

Summarizing: 

• Vocabulary: an agreed list of names of things
• Dictionary: vocabulary + gives definitions to named things
• Taxonomy: vocabulary + dictionary + orders things in a classification hierarchy
• Ontology: vocabulary + dictionary + taxonomy + adds relationships and properties to things

The CB-NL contains names of things, definitions, a taxonomy, and relationships between concepts, making it an ontology.

Quick intro to CB-NL terms

For a good understanding of CB-NL and this wiki it is important to explain a few key concepts. 

The first terms that need explanation are "Concept" and "Concept library". In the CB-NL, concepts are common things with their definitions, that exist within the Building and Infrastructure domains. For example, the concept 'Bridge'. In the CB-NL this is not a description of a physically existing bridge, but a commonly holding definition, which can in principle be true for all possible bridges in the world. In the CB-NL such a thing is called a 'concept' and not an 'object' Bridge, because the term 'object' is commonly associated with tangible things. For the same reason the CB-NL is a 'concept library' and not an 'object library'. The latter would by a lot of people be understood as something like a product catalogue. 

In the CB-NL, these concepts are ordened in a structure: a taxonomy. In this structure each concept has one or more higher, more abstract parent concepts (supertypes) and one or more lower, more concrete child concepts (subtypes). The supertype of 'Brug', for example, is
'Overbrugging' and subtypes of 'Brug' are, for example, 'Beweegbare brug', 'Vaste brug', 'Verkeersbrug' en 'Spoorbrug'. 

An important aspect of the CB-NL is that a subtype inherits all characteristics from its supertype. Besides these inherited characteristics, subtypes always have a characteristic that distinguishes it from its supertype, i.e. that makes it different. For example, 'Verkeersbrug' differs from its supertype 'Brug' in that it has the application 'Wegverkeer'.  This distinguishing characteristic is called a 'discriminator' in CB-NL. 

Of course, there is an end to the levels of supertypes that exist. The highest, most abstract levels are together called the 'Top level'. 

Core and contexts

The CB-NL Core is filled with concepts from a number of pre-existing sources. Semantic Concepts (SC), Cheobs, OTL Rijkswaterstaat and IMGeo are the primary sources for the information that is found in CB-NL. 

Contexts are external concept libraries that are mapped to the CB-NL.