Semantic Web

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The Semantic Web is a concept originated by Tim Berners-Lee and a set of technologies and practices developed out of this vision. Simply put, the Semantic Web is a Web whereby collections of assertions about the state of the world are linked together in much the same way as web pages are. What differentiates the Semantic Web from existing data structures is the use of URIs to uniquely identify things, and relationships between things. The sort of problem scenario that Semantic Web technologies try to solve are those involving multiple disparate source of data - for instance, hooking together train timetables and class timetables, so a student can automatically plan their travel itinerary without having to manually match the data together.

The W3C have put forward a variety of standards built on top of the Resource Description Framework, a formal semantic model for representing things and the relationships between them.

Domain-specific semantic models

Medicine

Semantic models seem the major trend in expert support to medicine. As an example of how semantic methodologies are used, consider several isolated concepts, which could be considered "nouns":

• beta-adrenergic antagonists (i.e., beta blockers)
• bradycardia (i.e., slow pulse)
• asthma
• hypertension
• benign hand tremor

One of the notations for relationships is the Unified Medical Language System® (UMLS®). Informally, some of the "verb" semantic relationships among the above could be:

• beta-adrenergic antagonists TREAT hypertension and benign hand tremor
• beta-adrenergic antagonists CAUSE bradycardia
• beta-adrenergic antagonists TRIGGER asthma

"Hypertension" would have a number of other TREATS relations, from drug classes such as thiazide diuretics, angiotensin-II converting enzyme antagonists, calcium channel blockers, angiotensin-II receptor blockers, etc.

ULMS is now being extended with formal ontologies: