Special Slots

• Definition: This slot is mandatory in all concepts and instances. It has only a Value facet whose filler is a definition of the concept in English intended only for human consumption.
• Time-Stamp: This is used to encode a signature showing who created this concept and when as well as updates done to the concept. It may be noted that not all concepts have an up to date Time-Stamp since the tools we have been using have and have not provided this feature at various times.
• Referenced-By-Token: This slot has been used in the past to encode a sentence from some source which led to a need for this concept. Many English sentences were thus inserted into concept frames in the past. In the current multi-lingual setup of this project, we have done away with this slot (mainly because of inconsistent ways of encoding the example sentences in the ontology we started with). This slot perhaps belongs only in a lexicon and will not be used in our ontology.
• Is-A: This slot is mandatory for all concepts except ALL which is the root of the hierarchy. Instances do not have an Is-A slot. This slot has only a Value facet which is filled by the names of the immediate parents of the concept. A concept missing an Is-A slot is called an orphan. Ideally, only ALL should be an orphan.
• Subclasses: This slot is mandatory for all concepts except leaves (which do not have other concepts as their immediate children). Concepts that only have instances as children do not have this slot. This slot also has only a Value facet which is filled by the names of the immediate children of the concept.
• Instances: This slot is present in any concept that has instances as children. A concept may have both Subclasses and Instances. There is no requirement that only leaf concepts have instances. This slot also has only a Value facet filled by the names of the instances of this concept.
• Instance-Of: This slot is mandatory for all instances and is present only in instances. It has only a Value facet which is filled by the name of the parent concept. Question: Can there be more than one parent concept for an instance? It seems possible.
• Inverse: This slot is present in all Relations and only in Relations. It has only a Value facet which is filled by the name of the Relation which is the Inverse of this Relation.
• Domain: This slot is present in all Properties and only in Properties. It has only a Sem facet which is filled by the names of concepts which can be in the domain of this Relation or Attribute. A Domain slot never has a Value facet since there is never an instance of a Property. A Property enters a text meaning representation (TMR) only as a slot in an instance of an OBJECT, EVENT, or other TMR constructs (such as TMR Relations).
• Range: This slot is also present in all Properties and only in Properties. It too has only a Sem facet. In Relations, the filler of the Sem facet is the names of concepts that are in the range of this Relation. In an Attribute, the Sem facet is filled by all the possible literal or numerical values permissible for that Attribute. The filler can also be a numerical range specific using appropriate mathematical comparison operators (such as >, <, ...). Again, the Range slot never has a Value facet since there is never an instance of a Property in a TMR other than as a slot in some other instance.

All other slots have Sem facets in concepts and Value facets in instances. Any slot either in a concept or in an instance may have in addition a Default, a Salience, or a Measuring-Unit facet. These facets have only been used sparingly in the current ontology. In fact, the Salience facet has never been used. It may also be noted that no slot is mandatory in these non-special slots. For example, a slot may have just a Default facet specified (with the implication that there is no constraint on other possible values for the filler).