Gellish

Gellish is a controlled natural language in which information and knowledge can be expressed so that it is computer interpretable, but still system independent. Gellish is a structured subset of natural language that is suitable for information and knowledge representation and as a successor of electronic data interchange. From a data modeling perspective it is a generic data model that includes domain specific knowledge and semantics.

Overview

Gellish is intended for the expression of complete and unambiguous specifications of products, facilities and processes, and for information about their purchasing, fabrication, installation, operation and maintenance and for the exchange of such information between systems, although in a system independent and computer interpretable way. It is also intended for the expression of knowledge about such things.

The definition of Gellish includes a large 'smart dictionary' of concepts with relations between those concepts, called STEPlib. It is called a 'smart dictionary', because the concepts are arranged in subtype-supertype hierarchy, making it a taxonomy which supports inheritance (computer science) of properties from supertype concepts to subtype concepts. Furthermore, because together with other relations between the concepts the smart dictionary is extended into an ontology (computer science). Gellish has an object-relation-object structure and therefor it includes the definition of a large number of standard relation types.

In principle, for every natural language there is a Gellish variant that is specific for that language. For example, Gellish Dutch (Gellish Nederlands), Gellish German (Gellish Deutsch), Gellish English etc. Gellish does not invent its own terminology, such as Esperanto, but uses the terms from natural languages. Thus for example the Gellish English dictionary is an ordinary dictionary that is extended with additional concepts and with relations between the concepts.

For example, the Gellish dictionary contains definitions of concepts such as 'pump' and 'mass' and definitions of relations. For example relations that can be indicated by standard phrases, such as 'is a subtype of', 'is classified as a', 'has as aspect', and 'is quantified as'. This enables a computer to correctly interpret the Gellish expressions, especially when they are expressed in tabular form, such as a Gellish Table or in RDF/Notation3 as follows:

Full Gellish requires additional columns for unique identifiers, the language of the expression, the validity context, status, creation date, etc. Gellish Light only requires the three above columns, which does not support for example capabilities to distinguish homonyms, automated translation and version management, as is supported by Full Gellish.

The collection of standard relation types define the kinds of facts that can be expressed in Gellish. There are mainly three groups of relation types, being:
* Relation types for relations between kinds of things (classes). They are intended for the expression of knowledge. For example, the specialization relation on the first example line above,
* Relation types for relations between individual things. They are intended for the expression of information about individual things. For example the possession of an aspect relation on the third of the above lines.
* Relation types for relations between individual things and kinds of things. They are intended for links between individual things and general concepts in the dictionary (or to private extensions of that dictionary). For example the classification and qualification relations above.Anybody can extend the Gellish dictionary and the relation types with privately defined concepts.

A knowledge base with basic engineering knowledge is integrated with the Gellish Dictionary. That knowledge is itself expressed in Gellish. Typically the Gellish dictionary is used to select classes for classification or as standard terminology (metadata) or to harmonize data in various computer systems or as a tool in a search engine.

Gellish uses a numeric identifier for every concept. For example, 130206 (pump) and 1225 (is classified as a). This makes that the concepts are identified in a natural language independent way. A feature of that is that information and knowledge that is expressed in Gellish in one language variant can be automatically translated and presented in any other language variant for which a Gellish dictionary is available. For example, a computer can automatically express the second above Gellish expression in German as follows:- P-123 'ist klassifiziert als ein' Zentrifugalpumpe

Gellish Database table

Gellish is typically expressed in the form of a Gellish Database [http://gellish.wiki.sourceforge.net/Gellish+Database] table.A Gellish Database table is a standard table that is suitable to represent any expression in the Gellish language. Its table columns are standardised. The table can be used as part of a database or as a data exchange file. A Gellish Database table can be implemented in any tabular format. For example, it can be implemented as a SQL based database or otherwise, as a STEPfile (according to ISO 10303-21), or as a simple spreadsheet table. The core of the table is equivalent with Notation 3 for RDF and consists also of three columns, whereas each line expresses a fact:
- a left hand object
- a relation type
- a right hand object

A full Gellish Database table has additional columns to express auxiliary facts that enable the use of synonyms and homonyms and multiple languages, unique identifiers for objects, roles and facts, validity contexts, units of measure, status, dates and references.

A difference between a Gellish Database table and RDF / Notation 3 is that Gellish English includes an English Dictionary of concepts and contains an extendable set of standard relation types, whereas RDF only defines a few basic concepts.

Gellish compared with OWL

OWL (Web Ontology Language) and Gellish are both meant for use on the semantic web. Nevertheless there are important differences between the two languages. The main differences are as follows:

1. Target audience and meta level
OWL is a metalanguage, including a basic grammar but without a dictionary. OWL is meant to be used by computer system developers and ontology developers to create ontologies. Gellish is a language, that includes a grammar as well as a dictionary and ontology. Gellish is meant to be used by computer system developers as well as by end users and can also be used by ontology developers when the Gellish ontology should be extended. Gellish does not make a distinction between a meta-language and a user-language, but the concepts from both 'worlds' are integrated in one language. So, the Gellish English dictionary contains concepts that are equivalent to the OWL concepts, but also contains the concepts from an ordinary English dictionary.

2. Vocabularies and ontologies
OWL can be used to explicitly represent the meaning of terms in vocabularies and the relationships between those terms. In other words: it can be used for the definition of taxonomies or ontologies. The terms in such a vocabulary do not become part of the OWL language. So OWL does not include definitions of the terms in a natural language such as road, car, bolt or length. However, it can be used to define them and to build an ontology.
The upper ontology part of Gellish can also be used to define terms and the relations between them. However, many of such natural language terms are already defined in the lower part of the Gellish dictionary / taxonomy / ontology itself. So in Gellish, terms such as road, car, bolt or length are part of the Gellish language. Therefore, Gellish English is a subset of natural English.

3. Synonyms and multi-language capabilities
Gellish makes a distinction between concepts and the various terms that are used as names (synonyms, abbreviations and translations) to refer to those concepts in different contexts and languages. Every concept is identified by a unique identifier that is natural language independent and can have many different terms in different languages to denote the concept. This enables automatic translation between different natural language versions of Gellish. In OWL the various terms in different languages and the synonyms are in principle different concepts that need to be declared to be the same by explicit equivalence relations. On one hand this is a simpler concept, but it makes automated translation significantly more complicated.

4. Upper ontology
OWL can be regarded as an upper ontology that consists of 54 'language constructs' (constructors or concepts). Gellish currently consists of over 40.000 concepts of which over 1000 belong to the upper ontology part. This indicates the large semantic richness and expression capabilities of Gellish. Furthermore, Gellish contains definitions of many facts about the defined concepts that are expressed as relationships between those concepts.

5. Extensibility
OWL has a fixed set of concepts (terms) that are only extended when the OWL standard is extended. Gellish is extensible by any user.

History

Gellish is a further development of ISO 10303-221 (AP221) and ISO 15926. Gellish is an integration and extension of the concepts that are defined in both standards. The specific philosophy of spatio-temporal parts to represent dicrete time periods without change to represent time is possible, but not necessary in Gellish. A subset of the Gellish Dictionary (STEPlib) is used to create ISO 15926-4.

External links and References

* [https://sourceforge.net/projects/gellish The Gellish dictionary and knowledge base] at SourceForge, which contains various documents about Gellish in the Download area, such as
- the Gellish English Application Handbook
- the Gellish Database table definition
- the Gellish Database extension manual.
- various sets of guidelines and examples.The project website also contains a downloadable version of the full Gellish English Dictionary (STEPlib).

* [http://www.dupress.nl/loadtop/dup_load.php?isbn=9789040725975 Gellish, an extensible ontological language]