Jena Eyeball manual

This document describes Eyeball, an "RDF lint". See the release notes for descriptions of changes from previous versions. Eyeball is part of the Jena family of RDF/OWL tools. For help and support with Eyeball, please see the Jena support page

Throughout this document, the prefix eye: stands for the URL http://jena.hpl.hp.com/Eyeball\#.

Introduction

Eyeball is a library and command-line tool for checking RDF and OWL models for various common problems. These problems often result in technically correct but implausible RDF. Eyeball checks against user-provided schema files and makes various closed-world assumptions.

Eyeball can check for:

  • unknown [with respect to the schemas] properties and classes
  • bad prefix namespaces
  • ill-formed URIs, with user-specifiable constraints
  • ill-formed language tags on literals
  • datatyped literals with illegal lexical forms
  • unexpected local names in schema namespaces
  • untyped resources and literals
  • individuals having consistent types, assuming complete typing
  • likely cardinality violations
  • broken RDF list structures
  • suspected broken use of the typed list idiom
  • obviously broken OWL restrictions
  • user-specified constraints written in SPARQL

Eyeball's checks are performed by Inspector plug-ins and can be customised by the user. Rendering its reports to output is performed by Renderer plug-ins which can also be customised by the user.

Installation

Fetch the Eyeball distribution zipfile and unpack it somewhere convenient. Eyeball 2.1 comes with its own copy of Jena 2.5 with CVS updates. Do not attempt to use other versions of Jena with Eyeball. TODO is this still true? -ed

In the Eyeball distribution directory, run the Eyeball tests:

ant test

If these tests fail, something is wrong. Please ask on the user mailing list or file a Jira issue.

If the tests have passed, you can use Eyeball from the installation directory, or copy lib, etc and mirror to somewhere convenient.

Command line operation

You must ensure that all the Eyeball jars from lib are on your classpath. (Note that Eyeball comes with its own Jena jar files and may not work with other Jena jars.) The directories etc and mirror should be in the current directory or also on your classpath.

Run the Eyeball command:

java [java options eg classpath and proxy] jena.eyeball
    (-check | -sign | -accept) specialURL+
    [-assume Reference*]
    [-config fileOrURL*]
    [-set Setting*]
    [-root rootURI]
    [-render Name]
    [-include shortName*]
    [-exclude shortName*]
    [-analyse | -repair]
    [-remark] [-version]

The -whatever sections can come in any order and may be repeated, in which case the additional arguments are appended to the existing ones. Exactly one of -check, -sign, -accept, or version must be provided; all the other options are optional.

When Eyeball resolves ordinary filenames or URLs it uses the Jena file manager to possibly map those names (eg to redirect an http: URL to a local cached copy). See the file manager howto for details on how to configure the file manager.

Examples of command-line use

java jena.eyeball -version

java jena.eyeball -check myDataFile.rdf

java jena.eyeball -assume dc -check http://example.com/nosuch.n3

java jena.eyeball -assume mySchema.rdf -check myData.rdf -render xml

java jena.eyeball -check myData.rdf -include consistent-type

java jena.eyeball -check myConfig.ttl -sign >signedConfig.ttl

-check specialURL+

The -check command checks the specified models for problems. The specialURLs designate the models to be checked. In the simplest case, these are plain filenames, file: URLs, or http: URLs. At least one specialURL must be specified. Each specified model is checked independently of the others.

-check myModel.ttl
-check file:///c:/rdf/pizza.owl
-check http://example.com/rdf/beer.rdf

If the specialURL is of the form ont:NAME:base, then the checked model is the model base treated as an OntModel with the specification OntModelSpec.<i>NAME</i>; see the Jena ontology documentation for the available names.

-check ont:OWL_MEM_RDFS_INF:myModel.ttl
-check ont:OWL_DL_MEM_RULE_INF:http://example.com/rdf/beer.rdf

If the specialURL is of the form ja:R@AF, then the model is that described by the resource R in the Jena assembler description file AF. R is prefix-expanded using the prefixes in AF.

-check ja:my:root@my-assembly.ttl
-check ont:OWL_MEM_RDFS_INF:my:root@my-assembly.ttl

If the URL (or the base) is of the form jdbc:DB:head:model, then the checked model is the one called model in the database with connection jdbc:DB:head. (The database user and password must be specified independently using the jena.db.user and jena.db.password system properties.)

-check jdbc:mysql://localhost/test:example

-config fileOrURL and -root rootURI

The -config fileOrURL options specify the Eyeball assembler configuration files to load. A single configuration model is constructed as the union of the contents of those files. If this option is omitted, the default configuration file etc/eyeball-config.n3 is loaded. See inside the Eyeball configuration file for details of the configuration file.

-config my-hacked-config-file.n3
-config etc/eyeball-config.n3 extras.ttl

The -root rootURI option specifies the root resource in the Eyeball configuration. If this option is omitted, eye:eyeball is used by default. rootURI is prefix-expanded using the prefixes in the configuration file.

-root my:root
-root my:sparse-config
-root urn:x-hp:eyeball-roots:special

-set Setting*

The -set option allows command-line tweaks to the configuration, eg for enabling checking URIs for empty local names. You will rarely need to use this; it is presented here because of its association with the -config and -root options.

Each Setting has the form S.P=O and adds the statement (S' P' O') to the configuration.

The current Eyeball converts the components of the S.P=O string into RDF nodes S', P', O' using some special rules:

  • A component starting with a digit is treated as an xsd:integer literal (and hence should only appear as the object of the setting).
  • A component starting with a quote, either " or ', is treated as a literal whose lexical form extends to the matching closing quote. Note: (a) literals with embedded spaces are not supported; (b) your command-line interpreter may treat quotes specially, and to allow the quotes to pass through to Eyeball, you'll have to use another (different) pair of quotes!
  • A component starting with _ is treated as a blank node with that label.
  • Otherwise, the component is treated as a URI reference. If it starts with a prefix (eg, rdf:) that prefix is expanded using the prefixes of the configuration file. If it has no prefix, it is as though the empty prefix was specified: in the default configuration file, that is set to the Eyeball namespace, so it is as though the prefix eye: had been used.

For example, to enable the URI inspectors non-default reporting of URIs with empty local names, use:

-set URIInspector.reportEmptyLocalNames="'true'"

Note the nested different quotes required to pass 'true' to Eyeball so that it can interpret this as a literal.

-include/-exclude shortNames

The various Eyeball inspectors are given short names in the configuration file. By default, an Eyeball check uses a specific set of inspectors with short name defaultInspectors. Additional inspectors can be enabled using the -include option, and default inspectors can be disabled using the -exclude option. See below for the available inspectors and their short names, and see inspectors configuration for how to configure inspectors.

-include list all-typed
-exclude cardinality
-include owl -exclude consistent-type

-assume Reference

The -assume References identifies any assumed schemas used to specify the predicates and classes of the data model. The reference may be a file name or a URL (and may be mapped by the file manager).

Eyeball automatically assumes the RDF and RDFS schemas, and the built-in XSD datatype classes. The short name owl can be used to refer to the OWL schema, dc to the Dublin Core schema, dcterms to the Dublin Core terms schema, and dc-all to both.

-assume owl
-assume owl dc-all
-assume owl my-ontology.owl

-sign and -accept (experimental)

If -sign is specified, Eyeball first does a -check. If no problem reports are generated, Eyeball writes a signed version of the current model to the standard output. The signature records the Eyeball configuration used and a weak hash of the model. If the input model is already signed, that signature is discarded before computing the new signature and writing the output.

If -accept is specified, the model is checked for its signature. If it is not signed, or if the signature does not match the content of the model -- either the hash fails, or the recorded configuration is not sufficient -- a problem is reported; otherwise not.

The intended use of -sign and -accept is that an application can require signed models which have passed some minimum set of inspections. The application code can then rely on the model having the desired properties, without having to run potentially expensive validation checks every time a model is loaded.

Important. Model signing is intended to catch careless mistakes, not for security against malicious users.

-version

Eyeball will print its version on the standard error stream (currently "Eyeball 2.1 (Nova Embers)").

-remark

Normally Eyeball issues its report or signed model to the standard output and exits with code 0 (success) or 1 (failure) with no additional output. Specifying -remark causes it to report success or some problems reported to standard error.

-repair and -analyse (experimental)

These operations are not currently documented. Try them at your peril: -repair may attempt to update your models.

-render Name

The eyeball reports are written to the standard output; by default, the reports appear as text (RDF rendered by omitting the subjects - which are all blank nodes - and lightly prettifying the predicate and object). To change the rendering style, supply the -render option with the name of the renderer as its value. Eyeball comes with N3, XML, and text renderers; the Eyeball config file associates renderer names with their classes.

-render n3
-render rdf

setting the proxy

If any of the data or schema are identified by an http: URL, and you are behind a firewall, you will need specify the proxy to Java using system properties; one way to do this is by using the Java command line options:

    -DproxySet=true
    -DproxyHost=theProxyHostName
    -DproxyPort=theProxyPortNumber

Inspectors shipped with Eyeball

Eyeball comes with a collection of inspectors that do relatively simple checks.

PropertyInspector (short name: "property")

Checks that every predicate that appears in the model is declared in some -assumed schema or owl:imported model -- that is, is given rdf:type rdf:Property or some subclass of it.

ClassInspector (short name: "presumed-class")

Checks that every resource in the model that is used as a class, ie that appears as the object of an rdf:type, rdfs:domain, or rdfs:range statement, or as the subject or object of an rdfs:subClassOf statement, has been declared as a Class in the -assumed schemas or in the model under test.

URIInspector (short name: "URI")

Checks that every URI in the model is well-formed according to the rules of the Jena IRI library. May apply additional rules specified in the configuration file: see uri configuration later for details.

LiteralInspector (short name: "literal")

Checks literals for syntactically correct language codes, syntactically correct datatype URIs (using the same rules as the URIInspector), and conformance of the lexical form of typed literals to their datatype.

PrefixInspector (short name: "prefix")

The PrefixInspector checks that the prefix declarations of the model have namespaces that are valid URIs and that if the prefix name is "well-known" (rdf, rdfs, owl, xsd, and dc) then the associated URI is the one usually associated with the prefix.

The PrefixInspector also reports a problem if any prefix looks like an Jena automatically-generated prefix, j.<i>Number</i>. (Jena generates these prefixes when writing RDF/XML if the XML syntactically requires a prefix but the model hasn't defined one.)

VocabularyInspector (short name: "vocabulary")

Checks that every URI in the model with a namespace which is mentioned in some schema is one of the URIs declared for that namespace -- that is, it assumes that the schemas define a closed set of URIs.

The inspector may be configured to suppress this check for specified namespaces: see vocabulary configuration later.

OwlSyntaxInspector (short name: "owl")

This inspector looks for "suspicious restrictions" which have some of the OWL restriction properties but not exactly one owl:onProperty and exactly one constraint (owl:allValuesFrom, etc).

SparqlDrivenInspector (short name: "sparql")

The SparqlDrivenInspector is configured according to configuring the SPARQL-driven inspector, and applies arbitrary SPARQL queries to the model. The queries can be required to match or prohibited from matching; a problem is reported if the constraint fails.

AllTypedInspector (short name: "all-typed")

Checks that all URI and bnode resources in the model have an rdf:type property in the model or the schema(s). If there is a statement in the configuration with property eye:checkLiteralTypes and value eye:true, also checks that every literal has a type or a language. Not in the default set of inspectors.

ConsistentTypeInspector (short name: "consistent-type")

Checks that every subject in the model can be given a type which is the intersection of the subclasses of all its "attached" types -- a "consistent type".

For example, if the model contains three types Top, Left, and Right, with Left and Right both being subtypes of Top and with no other subclass statements, then some S with rdf:types Left and Right would generate this warning.

CardinalityInspector (short name: "cardinality")

Looks for classes C that are subclasses of cardinality restrictions on some property P with cardinality range min to max. For any X of rdf:type C, it checks that the number of values of P is in the range min..max and generates a report if it isn't.

Literals are counted as distinct if their values (not just their lexical form) are distinct. Resources are counted as distinct if they have different case-sensitive URIs: the CardinalityInspector takes no account of owl:sameAs statements.

ListInspector (short name: "list")

The ListInspector performs two separate checks:

  • looks for lists that are ill-formed by having multiple or missing rdf:first or rdf:rest properties on their elements.
  • looks for possible mis-uses of the "typed list" idiom, and reports the types so defined.

The typed list idiom is boilerplate OWL for defining a type which is List-of-T for some type T. It takes the form:

my:EList a owl:Class
    ; rdfs:subClassOf rdf:List
    ; rdfs:subClassOf [owl:onProperty rdf:first; owl:allValuesFrom my:Element]
    ; rdfs:subClassOf [owl:onProperty rdf:rest; owl:allValuesFrom my:EList]
    .

The type my:Element is the element type of the list, and the type EList is the resulting typed list. The list inspector checks that all the subclasses of rdf:List (such as EList above) that are also subclasses of any bnode (such as the two other superclasses of EList)that has any property (eg, owl:onProperty) that has as an object either rdf:first or rdf:rest is a subclass defined by the full idiom above: if not, it reports it as a suspectListIdiom.

Eyeball problem reports

Eyeball generates its reports as items in a model. Each item has rdf:type eye:Item, and its other properties determine what problem report it is. The default text renderer displays a prettified form of each item; use -render n3 to expose the complete report structure.

One of the item's properties is its main property, which identifies the problem; the others are qualifications supplying additional detail.

PropertyInspector: predicate not declared

[] eye:unknownPredicate "*URIString*".

The predicate with the given URI is not defined in any of the -assumed schemas.

ClassInspector: class not declared

[] eye:unknownClass "*URIString*".

The resource with the given URI is used as a Class, but not defined in any of the -assumed schemas.

URIInspector: bad URI

[] eye:badURI "*URIString*"; eye:forReason *Reason*.

The URIString isn't legal as a URI, or is legal but fails a user-specified spelling constraint. Reason is a resource or string identifying the reason.

reason explanation
eye:uriContainsSpaces the URI contains unencoded spaces, probably as a result of sloppy use of file: URLs.
eye:uriFileInappropriate a URI used as a namespace is a file: URI, which is inappropriate as a global identifier.
eye:uriHasNoScheme a URI has no scheme field, probably a misused relative URI.
eye:schemeShouldBeLowercase the scheme part of a URI is not lower-case; while technically correct, this is not usual practice.
eye:uriFailsPattern a URI fails the pattern appropriate to its schema (as defined in the configuration for this eyeball).
eye:unrecognisedScheme the URI scheme is unknown, perhaps a misplaced QName.
eye:uriNoHttpAuthority an http: URI has no authority (domain name/port) component.
eye:uriSyntaxFailure the URI can't be parsed using the general URI syntax, even with any spaces removed.
eye:namespaceEndsWithNameCharacter a namespace URI ends in a character that can appear in a name, leading to possible ambiguities.
eye:uriHasNoLocalname a URI has no local name according to the XML name-splitting rules. (For example, the URI http://x.com/foo#12345 has no local name because a local name cannot start with a digit.)
"did not match required pattern Taili for prefix Head". This badURI starts with Head, but the remainder doesn't match any of the Tailis associated with that prefix.
"matched prohibited pattern Tail for prefix Head". This badURI starts with Head, and the remainder matched a prohibited Tail associated with that prefix.

LiteralInspector: illegal language code

[] eye:badLanguage "*badCode*"; eye:onLiteral "*spelling*".

A literal with the lexical form spelling has the illegal language code badCode.

LiteralInspector: bad datatype URI

[] eye:badDatatypeURI "*badURI*"; eye:onLiteral "*spelling*".

A literal with the lexical form spelling has the illegal datatype URI badURI.

LiteralInspector: bad lexical form

[] eye:badLexicalForm "*spelling*"; eye:forDatatype "*dtURI*".

A literal with the datatype URI dtURI has the lexical form spelling, which isn't legal for that datatype.

PrefixInspector: bad namespace URI

[] eye:badNamespaceURI "*URIString*" ; eye:onPrefix "*prefix*" ; eye:forReason *Reason*.

The namespace URIString for the declaration of prefix is suspicious for the given Reason (see the URIInspector reports for details of the possible reasons).

PrefixInspector: Jena prefix found

[] eye:jenaPrefixFound "*j.Digits*"; eye:forNamespace "*URIString*".

The namespace URIString has an automatically-generated Jena prefix.

PrefixInspector: multiple prefixes for namespace

[] eye:multiplePrefixesForNamespace "*NameSpace*" ; eye:onPrefix "*prefix<sub>1</sub>"* ...

There are multiple prefix declarations for NameSpace, namely, prefix1 etc.

VocabularyInspector: not from schema

[] eye:notFromSchema "*NameSpace*"; eye:onResource *Resource*.

The Resource has a URI in the NameSpace, but isn't declared in the schema associated with that NameSpace.

OwlSyntaxInspector: suspicious restriction

[] eye:suspiciousRestriction *R*; eye:forReason *Reason*...

The presumed restriction R is suspicious for the given Reasons:

  • eye:missingOnProperty -- there is no owl:onProperty property in this suspicious restriction.
  • eye:multipleOnProperty -- there are multiple owl:onProperty properties in this suspicious restriction.
  • eye:missingConstraint -- there is no owl:hasValue, owl:allValuesFrom, owl:someValuesFrom, or owl:[minC|maxC|c]ardinality property in this suspicious restriction.
  • eye:multipleConstraint -- there are multiple constraints (as above) in this suspicious restriction.

The restriction R is identified by (a) supplying its immediate properties, and (b) identifying its named equivalent classes and subclasses.

SparqlDrivenInspector: require failed

[] eye:sparqlRequireFailed "*message*".

A SPARQL query that was required to succeed against the model did not. The message is either the query that failed or a meaningful description, depending on the inspector configuration.

SparqlDrivenInspector: prohibit failed

[] eye:sparqlProhibitFailed "*message*".

A SPARQL query that was required to fail against the model did not. The message is either the query that succeeded or a meaningful description, depending on the inspector configuration.

AllTypedInspector: should have type

[] eye:shouldHaveType *Resource*.

The Resource has no rdf:type. Note that when using models with inference, this report is unlikely, since inference may well give the resource a type even if it has no explicit type in the original model.

ConsistentTypeInspector: inconsistent types for resource

[] eye:noConsistentTypeFor *URI* ; eye:hasAttachedType *TypeURI<sub>i</sub>*
...

The resource URI has been given the various types TypeURIi, but if we assume that subtypes are disjoint unless otherwise specified, these types have no intersection.

The ConsistentTypeInspector must do at least some type inference. This release of Eyeball compromises by doing RDFS inference augmented by (very) limited union and intersection reasoning, as described in the Jena rules in etc/owl-like.rules, so its reports must be treated with caution. Even with these restrictions, doing type inference over a large model is costly: you may need to suppress it with -exclude until any other warnings are dealt with.

While, technically, a resource with no attached types at all is automatically inconsistent, Eyeball quietly ignores such resources, since they turn up quite often in simple RDF models.

CardinalityInspector: cardinality failure

[] eye:cardinalityFailure *Subject*; eye:onType *T*; eye:onProperty *P*

The Subject has a cardinality-constrained rdf:type T with owl:onProperty P, but the number of distinct values in the model isn't consistent with the cardinality restriction.

Additional properties describe the cardinality restriction and the values found:

  • eye:numValues N: the number of distinct values for (Subject, P) in the model.
  • eye:cardinality [eye:min min; eye:max max]: the minimum and maximum cardinalities permitted.
  • eye:values Set: A blank node of type eye:Set with an rdfs:member value for each of the values of P.

ListInspector: ill-formed list

[] eye:illFormedList *URI* ; eye:because [eye:element *index<sub>i</sub>*; *Problem<sub>i~*]~i</sub> ...

The list starting at URI is ill-formed because the element with index indexi had Problemi. The possible problems are:

  • eye:hasNoRest -- the element has no rdf:rest property.
  • eye:hasMultipleRests -- the element has more than one rdf:rest property.
  • eye:hasNoFirst -- the element has no rdf:first property.
  • eye:hasMultipleFirsts -- the element has more than one rdf:rest property.

ListInspector: suspect list idiom

[] eye:suspectListIdiom *Type*.

The resource Type looks like it's supposed to be a use of the "typed list idiom", but it isn't complete/accurate.

Inside the Eyeball configuration file

Configuration files

The Eyeball command-line utility is configured by files (or URLs) specified on the command line: their RDF contents are unioned together into a single config model. If no config file is specified, then etc/eyeball-config.n3 is loaded. The configuration file is a Jena assembler description (see Assemblers) with added Eyeball vocabulary.

Eyeball is also configured by the location-mapping file etc/location-mapping.n3. The Eyeball jar contains copies of both the default config and the location mapper; these are used by default. You can provide your own etc/eyeball-config.n3 file earlier on your classpath or in your current directory; this config replaces the default. You may provide additional location-mapping files earlier on your classpath or in your current directory.

Configuring schema names

To avoid having to quote schema names in full on the Eyeball command line, (collections of) schemas can be given short names. [] eye:shortName shortNameLiteral ; eye:schema fullSchemaURL ... .

A shortname can name several schemas. The Eyeball delivery has the short names rdf, rdfs, owl, and dc for the corresponding schemas (and mirror versions of those schemas so that they don't need to be downloaded each time Eyeball is run.)

Configuring inspectors

The inspectors that Eyeball runs over the model are specified by eye:inspector properties of inspector resources. These resources are identified by eye:shortNames (supplied on the command line). Each such property value must be a plain string literal whose value is the full name of the Inspector class to load and run; see the Javadoc of Inspector for details.

An inspector resource may refer to other inspector resources to include their inspectors, using either of the two properties eye:include or eye:includeByName. The value of an include property should be another inspector resource; the value of an includeByName property should be the shortName of an inspector resource.

Configuring the URI inspector

As well as applying the standard URI rules, Eyeball allows extra pattern-oriented checks to be applied to URIs. These are specified by eye:check properties of the URIInspector object in the configuration.

The object of an eye:check property is a bnode with eye:prefix, eye:prohibit, and eye:require properties. The objects of these properties must be string literals.

If a URI U can be split into a prefix P and suffix S, and there is a check property with that prefix, and either:

  • there's a prohibit property and S matches the object of that property, or
  • there's a require property and S does not match the object of that property,

then a problem is reported. If there are multiple prohibits, then a problem is reported if any prohibition is violated; if there are multiple requires, a problem is reported if none of them succeed.

eye:URIInspector eye:check
  [eye:prefix "urn:x-hp:"; eye:prohibit ".*:.*"]
  ; [eye:prefix "http://example.com/"; eye:require ".*eyeball.*"]

The prefixes, requires, and prohibits are treated as Java patterns. The URI inspector can be configured to report URIs with an empty local name. These arise because the meaning of "local name" comes from XML, and in XML a local name must start with an NCName character, typically a letter but not a digit. Hence URIs like http://example.com/productCode#1829 have an empty local name. This is sometimes confusing.

To report empty local names, add the property eye:reportEmptyLocalNames to the inspector eye:URIInspector with the property value true. You may edit the configuration file or use the -set command-line option.

Configuring the vocabulary inspector

The vocabulary inspector defaults to assuming that schema namespaces are closed. To disable this for specified namespaces, the inspector object in the configuration can be given eye:openNamespace properties.

The object of each of these properties must be a resource; the URI of this resource is an open namespace for which the inspector will not report problems.

eye:VocabularyInspector eye:openNamespace <http://example.com/examples#>

Configuring the SPARQL-driven inspector

The SPARQL inspector object in the configuration may be given eye:sparql properties whose objects are resources specifying SPARQL queries and problem messages.

eye:SparqlDrivenInspector eye:sparql [...]

The resource may specify a SPARQL query which must succeed in the model, and a message to produce if it does not.

eye:SparqlDrivenInspector eye:sparql
  [eye:require "select * where {?s ?p ?o}"; eye:message "must be non-empty"]

If the query is non-trivial, the string may contain a reference to a file containing the query, rather than the entire query.

eye:require "@'/home/kers/example/query-one.sparql'"

The quoted filename is read using the Jena file manager and so respects any filename mappings. "@" characters not followed by "'" are not subject to substitution, except that the sequence "@@" is replaced by "@".

Using eye:prohibit rather than eye:require means that the problem is reported if the query succeeds, rather than if it fails.

Configuring renderers

The renderer class that Eyeball uses to render the report into text is giving in the config file by triples of the form:

[]
  eye:renderer FullClassName
  ; eye:shortName ShortClassHandler

The FullClassName is a string literal giving the full class name of the rendering class. That class must implement the Renderer interface and have a constructor that takes a Resource, its configuration root, as its argument.

The ShortClassHandle is a string literal giving the short name used to refer to the class. The default short name used is default. There should be no more than one eye:shortName statement with the same ShortClassHandle in the configuration file, but the same class can have many different short names.

The TextRenderer supports an additional property eye:labels to allow the appropriate labels for an ontology to be supplied to the renderer. Each object of a eye:labels statement names a model; all the rdfs:label statements in that model are used to supply strings which are used to render resources.

The model names are strings which are interpreted by Jena's FileManager, so they may be redirected using Jena's file mappings.

Inside the Eyeball code

Eyeball can be used from within Java code; the command line merely provides a convenient external interface.

Creating an Eyeball

An Eyeball object has three subcomponents: the assumptions against which the model is to be checked, the inspectors which do the checking, and the renderer used to display the reports.

The assumptions are bundled into a single OntModel. Multiple assumptions can be supplied either by adding them as sub-models or by loading their content directly into the OntModel.

The inspectors are supplied as a single Inspector object. The method Inspector.Operations.create(List) creates a single Inspector from a list of Inspectors; this inspector delegates all its inspection methods to all of its sub-inspectors.

The renderer can be anything that implements the (simple) renderer interface.

To create an Eyeball:

Eyeball eyeball = new Eyeball( inspector, assumptions, renderer );

To eyeball a model

Models to be inspected are provided as OntModels. The problems are delivered to a Report object, where they are represented as an RDF model.

eyeball.inspect( report, ontModelToBeInspected )

The result is that same report object. The Report::model() method delivers an RDF model which describes the problems found by the inspection. The inspections supplied in the distribution use the EYE vocabulary, and are used in the standard reports:

Every report item in the model is a blank node with rdf:type eye:Item. See earlier sections for the descriptions of the properties attached to an Item.

Rebuilding Eyeball

The provided ant script can be used to rebuild Eyeball from source:

ant clean build jar

(Omitting clean will do an incremental build, useful for small changes.)

The libraries required by Eyeball are all in the lib directory, including the necessary Jena jars.

Creating and configuring an inspector

To make a new inspector available to Eyeball, a new Inspector class must be created and that class has to be described in the Eyeball configuration.

Creating an Inspector

Any inspector must implement the Inspector interface, which has four operations:

  • begin( Report r, OntModel assume ): Begin a new inspection. r is the Report object which will accept the reports in this inspection; assume is the model containing the assumed ontologies. begin is responsible for declaring this inspectors report properties.
  • inspectModel( Report r, OntModel m ): Do a whole-model inspection of m, issuing reports to r.
  • inspectStatement( Report r, Statement s ): Inspect the single statement s, issuing reports to r.
  • end( Report r ): Do any tidying-up reports required.

Typically end and one of inspectModel or inspectStatement do nothing.

An inspector must also have a constructor that takes a Resource argument. When Eyeball creates the Inspector object, it passes the Resource which is the root of this inspector's configuration. (This is, for example, how the SPARQL-driven inspector receives the query strings to use.)

Developers may find the class InpsectorBase useful; it has empty implementations for all the Inspector methods. They may also find InspectorTestBase useful when writing their inspector's tests, both for its convenience methods and because it requires that their class has the appropriate constructors.

Reports and report properties

Eyeball reports are statements in a report model. To let the renderer know which property of a report is the "main" one, and which order the other properties should appear in, the inspector's begin method should declare the properties:

r.declareProperty( EYE.badDatatypeURI );
r.declareOrder( EYE.badLanguage, EYE.onLiteral );

declareProperty(P) announces that P is a report property of this inspector. declareOrder(F,S) says that both F and S are report properties, and that F should appear before S in the rendered report.

Reports are made up of report items, which are the subjects of the report properties. To create a report item, use one of reportItem() or reportItem(S). The second form is appropriate when the report is attached to some statement S of the model being inspected; a report renderer will attempt to display S.

To add the main property to a report item R, use R.addMainProperty(P,O); to add non-main properties, use R.addProperty(P,O).

Configuring an inspector

To add an inspector to a configuration file, choose a URI for it (here we're using my:Fresh and assuming a prefix declaration for my:) and a short name (here, "fresh") and add a description to the configuration file:

my:Fresh a eye:Inspector
  ; eye:shortName "fresh"
  ; rdfs:label "fresh checks for my application"
  ; eye:className "full.path.to.Fresh"
  .

Replace full.path.to.Fresh with the full classname of your inspector. Now you can use Fresh by adding -include fresh to the Eyeball command line (and ensuring that the class is on your classpath).

If you want Fresh to be included by default, then you must add it as an eye:inspector property of the configuration root, eg:

eye:eyeball a eye:Eyeball
  ; eye:inspector
    eye:PrefixInspector,    # as delivered
    my:FreshInspector,      # new inspector
    eye:URIInspector,       # as delivered
    ...