Axioms and rules

Axioms and rules

In EthOn domain knowledge is expressed using OWL 2.0 axioms and SWRL rules.

Axioms are stated as a OWL statement, e.g. defining a class, a subclass or a property. Axioms can also state restrictions such as domain and range for properties.

Rules are used to express things that cannot be easily represented in OWL. SWRL is used as a rule language.

Examples

Axioms are sentences in description logic statements. At this early stage only a few axioms have been defined in EthOn. The expressiveness will increase as the structure of EthOn matures. The axioms can be used with reasoners to infer information from data. You can best have a look at them if you open EthOn in Protégé.

Some example axioms

Informal statement: Blocks have exactly one property blockHash of type xsd:hexBinary. EthOn axiom in Manchester Syntax: Class: Block SubClassOf: blockHash exactly 1 xsd:hexBinary SubClassOf Block

To be exact the axiom states "A Block is a subclass of the theoretical class of 'all things that have exactly one blockHash property with a value of type xsd:hexBinary'". We have specified a necessary but not sufficient condition. We are saying there might be other things that have a blockHash and are not Blocks.

Also, something that doesn't have such a property may still be a Block. We don't know, maybe it's just one that is not as well described (see open world assumption).

Informal statement: Blocks with a number of 0 are Genesis Blocks. EthOn axiom: Block and (number some {"0"^^xsd:int}) EquivalentTo GenesisBlock

Informal statement: When a Tx Receipt has a post Tx state, the Tx itself has a createsState property relation. EthOn axiom: hasReceipt o hasPostTxState SubPropertyOf: createsState