Semantic Layers

["CarlMattocks" <CarlMattocks@CHECKMi.com>]

Folks:

To ensure the 'discussion' on Semantic Layers (et al) has the appropriate focus - please peruse the assertions below and let me know :
>if it is too trivial
>what questions it prompts
>what it does not say
>where it could be used 

Semantic Layers

Classification
Semantic layers use semantic relationships and controlled vocabularies to increase the meaning of metadata and provide context to items that have metadata properties . Historically, semantic layers have been used by (information) scientists to classify unstructured knowledge. Currently there is a lost of discussion about expanding the application of semantic layers to provide domain links for semi-structured information and structured information. Whatever the usage, the key benefits of using semantic layers are:
 The body of knowledge is partitioned into logical groupings 
 Users can discover information using a single word search term 
 Topic to sub-topic, drill down searches are supported 
 Domain scopes are declared 
 The ambiguities of the (English) language are less problematic

Controlled Vocabulary, Taxonomy, Thesaurus, Ontology, Business Model, Topic Maps? 
A simple lexicon that only contains the definition of words used by a particular group of professionals can be considered a controlled vocabulary. Ontologies, Taxonomies and Thesauri relate terms in a controlled vocabulary via parent-child and associative relationships. Business Models contain associative relationships, they also contain explicit grammar rules to constrain how to use controlled vocabulary terms to express (model) something meaningful within a domain of interest. More formally :

A controlled vocabulary is a list of elemental terms that have been enumerated explicitly. This list is controlled by and is available from an authority, such as, ACORD. Ideally, all elements in a controlled vocabulary have a unique label and an unambiguous, non-redundant definition, as in:
1. If  a (term) token of an element label is commonly used to mean different concepts in different contexts, then that token is explicitly qualified to resolve the ambiguity. 
2. If multiple terms are used to mean the same thing, they are considered (equally alternate) synonyms.

A thesaurus is a networked collection of controlled vocabulary terms. This means that a thesaurus uses associative relationships in addition to broader-narrower (parent-child) relationships, e.g. synonym. The expressiveness of the associative relationships in a thesaurus vary and can be as simple as “related to term” as in term A is related to term B.

A taxonomy is a collection of controlled vocabulary terms organized into a hierarchical structure. Each term in a taxonomy is in one or more parent-child relationships to other terms in the taxonomy. There may be different types of parent-child relationships in a taxonomy (e.g., whole-part, genus-species, type-instance). In a poly-hierarchy, a term can have multiple parents, yet it has the same children in every location.

An ontology can mean different things and the definition continues to evolve since developers of agent-based software consider that each (semantic) web service must be defined in un-ambiguous terms. That is, ontologies allow a web service to be ‘published’ using a language that expresses something meaningful within a specified domain of interest. Therein, the ontology grammar contains formal constraints (e.g., specifies what it means to be a well-formed statement, assertion, query, etc.). OWL Web Ontology Language can be used to explicitly represent the meaning of terms in vocabularies and the relationships between those terms. However, it is intended to be used when the information contained in documents needs to be processed by applications, as opposed to situations where the content only needs to be presented to humans.

A business model is an explicit model of the constructs and rules needed to map specific types of processing and data within a domain of interest e.g. namespace. Many accept the statement that the contents of a domain specific business model would contain the same type of knowledge as an ontology with the same scope. 

A Topic Map is an ISO standard for building knowledge about a domain and integrating this encoded knowledge to information resources that are considered relevant to the domain. Topic maps are organized around topics, which represent subjects of discourse; associations, representing relationships between the subjects; and occurrences, which connect the subjects to pertinent information resources.  The first version used SGML DTDs the latest version is based on  XSDs (schemas). A topic map processor is any module or system that can process topic maps. 



cheers
carl
Carl Mattocks
CEO CHECKMi
e-mail: CarlMattocks@checkmi.com
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