Table 2 in An Xper 3 reference guide for taxonomists: a collaborative system for identification keys and descriptive data

Table 2. Glossary of the terms used in Xper3. TermDefinitionapplicability or inapplicabilityStatus of a descriptor in a description. A descriptor is applicable in a description if the description does not contain an eliminatory state as an attribute value for the parent descriptor.attributeData associating an item and a descriptor. In the case of a categorical descriptor, an attribute can be one or a set of states if expressing polymorphism is needed for the item. In the case of a numerical descriptor, the attribute is a statistical distribution of values expressed by its minimum and maximum or by its mean and standard deviation. Syn. element description.calculated descriptorA descriptor whose values are automatically calculated from other data using logical (Boolean) operators.categorical descriptorA descriptor taking as possible values qualitative states, or numeric intervals. Examples: “Blade shape”; “Number of antenna articles” with states “less than five”; “five to ten”; “more than ten”. A descriptor that takes qualitative states or numerical intervals as possible values. Examples: “blade shape”; “number of antennae articles” with states “less than five”; “five to ten”; “more than ten”.checkbaseA tool to check the consistency of the descriptions and to compare them in pairs.descriptionSet of attributes relating to the same item.descriptive modelSet of descriptors with their relationships (hierarchy) and their list of states or metrics. The descriptive model defines the common terminology for all the descriptions in a knowledge base.descriptorElement used to describe items, essentially a character for taxonomists, or a trait for ecologists.discriminant powerAbility of a descriptor to distinguish between items.elimination stateState used in a rule to define the condition of inapplicability of a descriptor.extensionVolume of the representation space corresponding to the description of an item. It is therefore the set of single descriptions (without variability, one value per descriptor) compatible with the item description.groupGrouping, under a chosen heading, a set of objects of the same nature; a set of descriptors, or a set of items.Ikey+Web service for generating a single-access identification key.itemObject which can be described in a knowledge base. For taxonomists, it usually is a taxon.keyA practical means to identify a specimen. We distinguish the interactive key (see Mkey+) and single access key (see IKey+).knowledge baseDataset in an Xper3 database.Mkey+Web service for multi-access interactive identification key.numerical descriptorA descriptor expressing a continuous numerical value, with a measurement unit, e.g., antenna length in mm.parent descriptorA descriptor used to define the rule of inapplicability of another descriptor (child descriptor).state (categorical state)A possible value of categorical descriptors, e.g., for a descriptor named “Colour of the eye”, its states could be “Blue”, “Black”, etc.unknown valueSpecial value to express ignorance. In case of an unknown value, Xper3 considers all the states or all the numerical values as equally possible.