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Materialized Reasoner | AllegroGraph 8.4.1

AllegroGraph has two different inference engines: one supports a superset of RDFS inference rules and the other supports OWL 2 RL. The first is called the dynamic RDFS++ reasoner because it generates inferred triples on-the-fly and does not save them in the triple-store. The second is an OWL 2 RL materializer: it uses a set of inference rules to generate new triples and adds them to the triple-store.

If the triple store is changed via additions or deletions then materialization may have to be run again so that the triple store contains the correct set of materialized triples.

The dynamic reasoner is best when:

• you do not need OWL 2 RL inference rules and
• the store you are using is changing.

The materializer is best when:

• OWL 2 RL inference is required or
• the store is relatively static.

OWL 2 RL is the subset of OWL 2 that is designed to support rule based reasoners. OWL 2 RL contains a large number of rules for generating triples and some rules for verifying that the triple store is consistent with respect to the OWL 2 RL ontology.

The complete OWL 2 RL rule set is described on the OWL 2 RL reference page.

There is New WebView interface, see the Manage reasoning item on the Repository Control submenu on the Repository menu, and a traditional AGWebView interface, see WebView, particularly the Repository Overview Page section; a Java interface, see AGMaterializer#newInstance() and AGRepositoryConnection#materialize; a Python interface, as well as the Lisp interface described below. There is also a command-line interface described next.

The program agtool materialize is the command-line version of the materializer. The agtool program is the general program for AllegroGraph command-line operations. (In earlier releases, there was a separate agmaterialize program.)

A user who wishes to materialize a repository must have read/write permission for that repo and must also be allowed to start sessions. See the Managing Users document for information on user permissions.

Here is an overview of its options:

Usage:

agtool materialize [OPTIONS] GROUND-REPO-SPEC 

The options are identified with a double dash when the full option name is used (--verbose) and a single dash when a single letter abbreviation is used (-v).

Materialization options:

--delete

Delete existing materialized triples and exit. No materialization is performed.

--display-ontology

Read and display the store's ontology and exit. No materialization is performed.

-f GRAPH, --graph GRAPH

May be specified multiple times. Materialization will be limited to triples whose graphs are among the graphs specified by instances of this argument. The --inferred-graph (abbreviated -g) will always be included, whether or not it is actually specified as a value of this argument.

-g GRAPH, --inferred-graph GRAPH

The graph into which inferred triples will be placed

--rule NAME

Specify materialization rule; can be used multiple times. Rules are: all, class, property, restriction, same-as, values-from.

--bulk

If specified, then materialization will be run in bulk mode. This mode provides approximately 30% faster materialization. Note that bulk mode is global to the store and means that transactions will not be durable (in particular, will not be logged). Therefore, the switch should generally be used only when the store is not being used for other operations and the store should be backed up when the materialization is complete.

Other options:

-v, --verbose

Include more output (this option may be repeated, the more times it appears, the more output will be provided).

Triple-store options:

-c CATALOG, --catalog CATALOG

This option is obsolete. The catalog is specified as part of the GROUND-REPO-SPEC.

-p PORT, --port PORT

This option is obsolete. The port is specified as part of the GROUND-REPO-SPEC.

GROUND-REPO-SPEC

This argument identifies the repository to be worked on. Its general form is

[USER:PASSWORD@][[HOST][:[PORT][s]]/][CATALOG:]REPO 

The s after the port number indicates the https scheme if present and the http scheme if absent. See the Repository Specification document for a complete description of repo specs.

The user must have read/write permission in REPO and also have permission to start sessions.

Examples

The repository is lubm-50 in catalog stores. The --rule, and --verbose options are specified (--verbose twice which means more information will be provided than if --verbose was just specified once):

agtool materialize --rule all --verbose -verbose stores:lubm-50 

Here is the same command run on a different host so the host running the AllegroGraph server (myhost), and the user (user1) and password (foo) must be supplied. The port is 12345 and the scheme is https:

agtool materialize --rule all --verbose -verbose user1:foo@myhost:123245s/stores:lubm-50  

The Lisp interface consists of two functions:

Materialize inferred triples based on a rule set. Returns the number of materialized triples added.

• db: specifies the triple store to materialize (defaults to *db*).

• commit: can be t, nil or the batch size as positive integer: if nil then the materializer will never commit (which is not a good idea if the database is large and there are many materialized triples); if positive integer then after this many triples are added to the triple store commit-triple-store will be called for that batch, and a commit will be done when the materializer is finished; if t then the previous case applies with a default batch size.

• delete-first?: if true (the default) then existing materialized triples are deleted first, before adding new materialized triples.

• delete-duplicates-first?: if true (the default) then duplicated triples are deleted before materializing as by delete-duplicate-triples (with :spog as mode). This prevents duplicated materialized triples.

• materialized-graph: the graph into which inferred triples will be added. The default is <http://franz.com/ns/allegrograph/4.12/materializer/defaultGraph>.

• print-ontology: will print the classes and properties found in the triple store.

• use-type-subproperty: change the implied predicate for subproperty reasoning

• verbose: Either true or a number. If true, then all materializer logging is sent to the log. Using a number can limit the amount of logging information generated with higher numbers indicating more logging. A level of 4 tends to present a reasonable amount of detail without being too overwhelming.

• with: either "all" or a list of the sets of rules to run (details below).

• without: a list of sets of rules to not run.

The symbolic names for the rulesets (which are written as string) are as follows. These are described in detail in the materializer documentation.

• "all"
• "same-as"
• "restriction"
• "values-from"
• "class"
• "property"

Note that "values-from" is a special subset of "restriction" rules. If "restriction" is specified then you can also specify "values-from" to enable that set of restriction rules

Remove any previously materialized triples. Returns the number of materialized triples deleted.

• db: specifies the triple store to materialize (defaults to *db*)

• commit: If true then commit-triple-store will be called once after the materialized triples are deleted; if false then the triple deletion will not be automatically committed to the store.

• materialized-graph: the graph from which materialized triples will be removed. The default is <http://franz.com/ns/allegrograph/4.12/materializer/defaultGraph>.

Examples of how to specify rulesets

(materialize-entailed-triples) 

will add the RDFS++ entailed triples.

(materialize-entailed-triples :with "all") 

will run all rules. Note that the result of this call may differ between versions of the materializer.

(materialize-entailed-triples :with  '("same-as" "restriction")) 

run the RDFS++ reasoning as well as "same-as" and "restriction".

(materialize-entailed-triples :with  '("values-from")) 

this is just basic RDFS++ reasoning as "restriction" was not specified as well so "values-from" is ignored.

(materialize-entailed-triples :without '("property"  "values-from")) 

run all rules except "property" and the "values-from" part of "restriction" reasoning.

The use-type-subproperty argument changes the triple which is generated in the following way:

Given:

classA rdfs:subClassOf classB  
mytype rdfs:subPropertyOf rdf:type  
objX   mytype          classA 

then:

we would normally generate this triple::

objX   rdf:type        classB 

but if use-type-subproperty is true then we will instead generate this triple:

objX   mytype          classB 

The table below is from the OWL 2 RL definition. We’ve added a second column where we describe how this rule is treated by the materializer.

Rules which are not implemented are numbered 1, 2, or 3 or have no number at all. The numbers indicate why they aren’t done. The rules with no number have not been considered yet for inclusion in the materializer and may appear in a future version.

Rules numbered 10 or 11 have been included in the materializer. Rules numbered 10 are part of the basic RDFS++ materializer and always run. Rules numbered 11 are implemented by another part of the materializer where they are run as independent rules. If the number 11 is followed by one or more ruleset names then those rulesets must be enabled for these rules to run.

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