GraphDB Constraint Validation

Consistency checks
GraphDB inference engine background
Operations on rulesets

GraphDB Enterprise supports consistency violation checks using standard OWL2RL semantics. It is possible to define rulesets that contain consistency rules.

Consistency checks

Materialisation and consistency mix: the rulesets support the definition of a mixture of materialization and consistency rules. This follows the existing naming syntax “id:” and “Consistency:”
Multiple named rulesets: GraphDB Enterprise supports multiple named rulesets.
No down time deployment: The deployment of new/updated rulesets can be done to a running instance.
Update transaction ruleset: Each update transaction can specify which named ruleset to apply. This is done by using “special” RDF statements within the update transaction.
Consistency violation exceptions: GraphDB Enterprise throws exceptions if a consistency rule is violated. The exception includes details as which rule has been violated and to which RDF statements.
Consistency Rollback: if a consistency rule is violated within an update transaction, the transaction will be rolled back and no statements will be committed.

GraphDB inference engine background

In order to instantiate an inferencer, first GraphDB requires the .pie file of each ruleset to be compiled. The process includes several steps:

Generating a java code out of the pie file contents using the built-in GraphDB rule compiler.
Compiling the java code (it requires JDK instead of JRE, hence the java compiler will be available through the standard java instrumentation infrastructure).
Instantiating the java code using a custom bytecode class loader.

In prior-GraphDB 6 versions, this inferencer was instantiated when the repository was initialized. The process was slow and took some time depending on the ruleset used and the rules included.
In GraphDB 6, the inferencer can be dynamically extended with new rulesets, as specified in the text section.

Operations on rulesets

All examples below use the sys: namespace, defined as:

Operation	Add a custom ruleset from .pie file
Predicate	sys:addRuleset
Description	Adds a custom ruleset from the specified .pie file. The ruleset is named after the filename, without the .pie extension.
Example	INSERT DATA { _:b sys:addRuleset <file://c:/graphdb/test-data/test.pie> } This creates a new ruleset "test". Note that under *nix (e.g. Linux) systems, if the file resides on e.g. /opt/rules/test.pie, it should be specified as <file:///opt/rules/test.pie>, i. e. with 3 slashes instead of two.

Operation	Add a built-in ruleset
Predicate	sys:addRuleset
Description	Adds a built-in ruleset (one of the rulesets that GraphDB supports natively)
Example	INSERT DATA { _:b sys:addRuleset "owl-max" } This adds the "owl-max" ruleset to the list of rulsets in the repository.

Operation	Add a custom ruleset with SPARQL INSERT
Predicate	sys:addRuleset
Description	Adds a custom ruleset from the specified .pie file. The ruleset is named after the filename, without the .pie extension.
Example	INSERT DATA { <:custom> sys:addRuleset "Prefices { a : http://a/ } Axioms {} Rules { Id: custom a b c a <a:custom1> c ----------------------- b <a:custom1> a } "} This creates a new ruleset "custom".

Operation	List all rulesets
Predicate	sys:listRulesets
Description	Lists all ruleset available in the repository.
Example	SELECT ?state ?ruleset { ?state sys:listRulesets ?ruleset }

Operation	Explore a ruleset
Predicate	sys:exploreRuleset
Example	SELECT * { ?content sys:exploreRuleset "test" }

Operation	Set a default ruleset
Predicate	sys:defaultRuleset
Description	Switches the default ruleset to the one, specified in the object literal.
Example	INSERT DATA { _:b sys:defaultRuleset "test" } This sets the default ruleset to "test". All transactions use this ruleset, unless they specify another ruleset as a first operation in the transaction.

Operation	Rename a ruleset
Predicate	sys:renameRuleset
Description	Renames the ruleset from "custom" to "test". Note that "custom" is specified as the subject URI in the default namespace.
Example	INSERT DATA { <:custom> sys:renameRuleset "test" }

This renames the ruleset "custom" to "test".

Operation	Delete a ruleset
Predicate	sys:removeRuleset
Description	Deletes the ruleset "test", specified in the object literal.
Example	INSERT DATA { _:b sys:removeRuleset "test" }

Operation	Consistency check
Predicate	sys:consistencyCheckAgainstRuleset
Description	Checks if the repository is consistent with the specified ruleset.
Example	INSERT DATA { _:b sys:consistencyCheckAgainstRuleset "test" }