OWLlink:
HTTP/XML Binding
Version 1.0
Working Group Recommendation 23 October 2009
- This version:
- http://www.owllink.org/owllink-httpxml-20091023/
- Latest version:
- http://www.owllink.org/owllink-httpxml/
- Previous version:
- http://www.owllink.org/owllink-httpxml-20081001/
- Authors:
- Olaf
Noppens, Ulm University
-
Marko Luther, DOCOMO Euro-Labs Munich
- Thorsten
Liebig, Ulm University
- Michael Wessel,
Racer Systems GmbH
- Contributors: (in alphabetic order)
- Sean
Bechhofer, The University of Manchester
- Matthew
Horridge, The University of Manchester
- Ralf
Möller, TU Hamburg
- Boris
Motik, Oxford University
- Peter F.
Patel-Schneider, Bell Labs Research, Alcatel-Lucent
- Dmitry
Tsarkov, The University of Manchester
- Anni-Yasmin
Turhan, TU Dresden
- Timo
Weithöner, formerly Ulm University
Abstract
The OWLlink interface provides an implementation-neutral
mechanism for accessing OWL reasoner functionality. OWLlink relies
on OWL 2 for the primitives of the modeling language, and is thus
fully compatible with OWL. The set of OWLlink primitives described
in this document cover basic reasoner managment, assertion of
axioms and elementary ask functionality. An extension mechanism is
provided in order to easily add any required functionality in a
controlled way to the core language. This document defines a
concrete binding of OWLlink into [HTTP/1.1] and [XML Schema]. A structural
specification of OWLlink is given in an accompanying document
[OWLlink
Structural Specification].
Summary of Changes
Since the latest Working Draft:
- Aligned with the latest OWLlink core specification as well as OWL 2
- OWLlink XML schema updated (w.r.t. latest OWL 2 schema)
- Examples added (prefix, load ontologies, etc.)
Please Comment
The OWLlink Working Group seeks public feedback on these Working
Drafts. Please send your comments to public-comments@owllink.org or post to the public
discussion forum at http://www.owllink.org/forum/.
1 Introduction
OWLlink is defined in terms of a structural specification
[OWLlink
Structural Specification]. The following describes a
binding of the specification to a concrete communication protocol,
namely XML over HTTP. Note that this is only one conceivable
binding. Other bindings may utilize [SOAP] or another particular Remote Message
Invocation protocol.
The HTTP/XML binding of OWLlink uses HTTP as its underlying
communication protocol for exchanging XML content between a
reasoner and a client. More technically, the reasoner has to accept
HTTP POST requests and responds as appropriate according to the
OWLlink specification. The requests as well as responses have to
consist of XML data according to the OWLlink HTTP/XML Schema. The
schema is obtained by a translation of the objects from the UML
diagrams of the OWLlink specification according to the translation
rules (see Section 2.2).
Note that the HTTP/XML binding is not intended to be
backwards compatible with existing implementations of the
[DIG 1.1] specification.
However, it relies on the [OWL 2 XML
Serialization] for the primitives of the ontology
language, and is thus fully compatible with OWL. As a result,
implementors of the XML binding of OWLlink can re-use their
implementation of OWL 2 parsers to parse the OWL 2 specific
contents of OWLlink primitives.
2 Binding
A common transport mechanism for communicating with an OWLlink
server is through the [HTTP/1.1] protocol. XML is a verbose
format and large Knowledge Bases may require a lot of information
to be transferred over the wire. It has been observed with DIG 1.1
implementations that this can introduce a considerable overhead
into the communication process. To alleviate this, OWLlink servers
should support the use of compression, with message pay-loads being
compressed before transfer. This may be realized by standard
compression technology of the HTTP/1.1 transport mechanism. For
instance, a server may include Content-Encoding:
gzip in the header of each HTTP message to specify that the
content has been compressed according to the gzip specification.
Alternatively, an OWLlink HTTP/XML implementation could make use of
methods developed within the Efficient XML Interchange initiative
[EXI]
2.1 Sessions and Messages
An OWLlink session is mapped to an HTTP connection and is
typically established upon sending the first request. HTTP servers
are in general allowed to close the HTTP connection at their own
discretion, which in effect terminates the OWLlink session. In
order to prevent this from happening, the client can include the
keepAlive in the header of each HTTP
request it sends. Note that closing an OWLlink session does not
imply the release of the Knowledge Base. OWLlink HTTP servers are
required to recognize this HTTP header and implement its
functionality according to the HTTP/1.1 specification.
Messages are sent using the HTTP POST
requests. The content type for messages is text/xml. The Content-Length must be explicitly set and confirm to
the HTTP standard.
2.2 XML Schema
The XML syntax for OWLlink is defined as an [XML Schema] within the
following document.
<http://www.owllink.org/owllink-xml-20091023.xsd>
It has been obtained by a straightforward translation of the
structural specification from the [OWLlink
Specification] in the following way:
- Each UML class that is intended to be instantiated is mapped to
a global element, whose sub-elements and attributes correspond to
the components of the UML class.
- Each UML class that is not intended to be instantiated
directly, but instead gathers together commonalities, is mapped to
a global element group, whose choice members correspond to the
children of the UML class.
- Each UML attribute is mapped to an XML attribute. If multiple
UML elements use the same attribute (e.g., GetObjectPropertiesBetween and GetObjectProprtiesOfFiller use the negative attribute as shown in [OWLlink
Specification], Figure
26) the UML attribute is mapped to a global XML attribute and
linked via a reference.
- If the owl.IRI class (cf.,
[OWLlink Specification], Figure 1) is
used in an association, it is always mapped to an (optional)
attribute labelled IRI and an (optional)
attribute labelled abbreviatedIRI. If the
owl.fullIRI class is used in an
association it is always mapped to an attribute (labelled according
to the association name) of the source class of the
association.
- The value attribute of the Literal class is mapped to an XML content.
- If the same structure is used in several UML classes (e.g.,
several KBRequests with one individual
and one object property) they are modeled as a XSD (complex) types
and re-used in their respective XML elements.
- In case the argument sequence of a request matters (is not only
a singleton or set) the order is specified due to the following
scheme:
- sub-super entity requests have a { sub-entitiy,
super-entity } argument order (cf. IsClassSubsumedBy)
- individual-class requests have an { individual, class
expression } order (cf. IsInstanceOf)
- property-individual related requests have a { [property
expression], [source individual], [target individual/literal] }
order where upt to two of the arguments are omitted (cf.
AreIndividualsRelated, GetDataPropertiesBetween).
Certain global conditions on OWLlink XML documents that are
related to the communication cannot be captured in an XML Schema,
i.e. the correspondence of requests and responses. Furthermore, the
root element of any OWLlink XML document written in this syntax
must be either RequestMessage for
bundling requests or ResponseMessage for
bundling responses.
The XML schema presented in this document covers the entire
OWLlink specification including all management, tell and ask
primitives.
2.3 OWLlink Requests and
Responses
Following a straightforward translation of the OWLlink
specification into a XML schema the content body of a HTTP message
is either the root element RequestMessage
or a ResponseMessage containing requests
resp. responses. Each Request need to be
acknowledged with a Response element as
described in the OWLlink specification document in the order
matching with the order of the corresponding requests.
<RequestMessage>
[request #1]
[request #2]
[ ... ]
[request #n]
</RequestMessage>
<ResponseMessage>
[response #1 (for request #1)]
[response #2 (for request #2)]
[ ... ]
[response #n (for request #n)]
</ResponseMessage>
If a server cannot process a request, it should attempt to
recover gracefully, and process other pending requests as if the
error did not happen. If, however, this recovery is not possible,
after sending the Error response, the server should close the
OWLlink session. If the OWLlink client or server detects a
violation of the HTTP protocol such as invalid headers, it should
respond as specified in the HTTP standard and then close the HTTP
connection, i.e. the OWLlink session.
3 Extensions
To enable the embedding of new requests and responses into XML
messages, implementors should use the redefinition mechanism of XML
Schema and extend the ol:Request and
ol:Response element groups. We strongly
encourage the definition of two files: one which contains the
schema file of the new elements with a separate namespace and one
file which redefines the OWLlink schema. Otherwise, if two
different extensions directly extend the OWLlink schema without
defining a new namespace it is not possible to use them at the same
time because XML schema does not allow for the redefinition of two
schemas at the same time.
For instance, let us assume that some extension defines a new
Knowledge Base request and an additional request with a
corresponding response. This extension can be defined in a separate
XML schema file with a separate namespace.
<?xml version="1.0"
encoding="UTF-8"?>
<xsd:schema
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:ol="http://www.owllink.org/owllink-xml#"
targetNamespace="http://www.owllink.org/ext/sample-xml#"
elementFormDefault="qualified"
attributeFormDefault="unqualified">
<xsd:import namespace="http://www.w3.org/2002/07/owl#"
schemaLocation="http://www.w3.org/2009/10/owl2-xml.xsd"/>
<xsd:import namespace="http://www.owllink.org/owllink-xml"
schemaLocation="http://www.owllink.org/owllink-xml-20091023.xsd"/>
<!-- simple
request without additional parameters -->
<xsd:element name="NewRequest1" type="ol:Request"/>
<!-- simple
KBRequest without additional parameters -->
<xsd:element name="NewKBRequest1" type="ol:KBRequest"/>
<!--
complex request -->
<xsd:element name="NewKBRequest2">
<xsd:complexType>
<xsd:complexContent>
<xsd:extension
base="ol:KBRequest"> [...definition...] </xsd:extension>
</xsd:complexContent>
</xsd:complexType>
</xsd:element>
<!--
complex response -->
<xsd:element name="NewResponse1">
<xsd:complexType>
<xsd:complexContent>
<xsd:extension
base="ol:Response"> [...definition...] </xsd:extension>
</xsd:complexContent>
</xsd:complexType>
</xsd:element>
<!--
complex KBResponse -->
<xsd:element name="NewKBResponse1">
<xsd:complexType>
<xsd:complexContent>
<xsd:extension
base="ol:KBResponse"> [...definition...] </xsd:extension>
</xsd:complexContent>
</xsd:complexType>
</xsd:element>
</xsd:schema>
The next step is to redefine the OWLlink schema. It is not
necessary to modify the original OWLlink file. Instead a new file
(e.g., sample-xml-20091023.xsd) according
to the following structure should be used:
<?xml version="1.0"
encoding="UTF-8"?>
<xsd:schema
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:ol="http://www.owllink.org/owllink-xml#"
xmlns:ext="http://www.owllink.org/sample-xml#"
targetNamespace="http://www.owllink.org/owllink-xml#"
elementFormDefault="qualified"
attributeFormDefault="unqualified">
<xsd:import namespace="http://www.w3.org/2002/07/owl#"
schemaLocation="http://www.w3.org/2009/10/owl2-xml.xsd"/>
<xsd:import namespace="http://www.owllink.org/sample-xml#"
schemaLocation="sample-xml-def-20091023.xsd"/>
<xsd:redefine schemaLocation="http://www.owllink.org/owllink-xml-20091023.xsd">
<xsd:group name="Request">
<xsd:choice>
<xsd:group
ref="ol:Request"/>
<xsd:element
ref="ext:NewRequest1"/>
<xsd:element
ref="ext:NewKBRequest1"/>
<xsd:element
ref="ext:NewKBRequest2"/>
</xsd:choice>
</xsd:group>
<xsd:group name="Response">
<xsd:choice>
<xsd:group
ref="ol:Response"/>
<xsd:element
ref="ext:NewResponse1"/>
<xsd:element
ref="ext:NewKBResponse1"/>
</xsd:choice>
</xsd:group>
</xsd:redefine>
</xsd:schema>
4 Examples
Here are several basic examples of OWLlink communication in
accordance with this specification. All the examples can be
downloaded at http://www.owllink.org/owllink-httpxml-20091023/examples/
4.1 Introspecting Reasoner
Capabilities
To introspect reasoner capabilities OWLlink offers the GetDescription request.
owllink-example-GetDescription-request-20091023.xml
<?xml version="1.0"
encoding="UTF-8"?>
<RequestMessage
xmlns="http://www.owllink.org/owllink-xml#"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.owllink.org/owllink-xml#
http://www.owllink.org/owllink-xml-20091023.xsd">
<GetDescription/>
</RequestMessage>
The answer response Description must
contained the reasoner name (e.g. MyOwnReasoner), the
version of the reasoner as well as of the supported OWLlink
protocol. In addition, the answer has to consist of a set of
supported settings (Setting element) and
(read-only) properties (Property element)
as well as the supported OWLlink extensions (Extension) and the public Knowledge Bases. For
instance, in the following sample response message the reasoner
states that it supports the following profiles: OWL 2 EL and
OWL DL. In addition, OWL 2 EL is used as the profile for newly
created Knowledge Bases by default. The default values can be
overridden for each Knowledge Base separately as shown in Section 4.2 . The ignoresAnnotations
Property informs that the reasoner
ignores annotation and that this behavior can not be changed.
owllink-example-GetDescription-response-20091023.xml
<?xml version="1.0"
encoding="UTF-8"?>
<!DOCTYPE ResponseMessage [
<!ENTITY ole "http://www.owllink.org/ext/">
]>
<ResponseMessage xmlns="http://www.owllink.org/owllink-xml#"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.owllink.org/owllink-xml#
http://www.owllink.org/owllink-xml-20091023.xsd">
<Description name="MyOwnReasoner">
<ProtocolVersion major="1"
minor="0"/>
<ReasonerVersion major="1"
minor="0"
build="0"/>
<Setting key="selectedProfile">
<OneOf
abbreviatedIRI="xsd:string">
<Literal>OWL
DL</Literal>
<Literal>OWL
2 EL</Literal>
</OneOf>
<Literal>OWL
2 EL</Literal>
</Setting>
<Property key="appliedSemantics">
<OneOf
abbreviatedIRI="xsd:string">
<Literal>RDF-based</Literal>
</OneOf>
<Literal>RDF-based</Literal>
</Property>
<Property key="supportedDatatypes">
<List
abbreviatedIRI="xsd:anyURI"/>
<Literal>http://www.w3.org/2001/XMLSchema#long</Literal>
<Literal>http://www.w3.org/2001/XMLSchema#int</Literal>
<Literal>http://www.w3.org/2001/XMLSchema#nonPositiveInteger</Literal>
<Literal>http://www.w3.org/2001/XMLSchema#nonNegativeInteger</Literal>
<Literal>http://www.w3.org/2001/XMLSchema#short</Literal>
<Literal>http://www.w3.org/2002/07/owl#real</Literal>
</Property>
<Setting key="abbreviatesIRIs">
<Datatype
abbreviatedIRI="xsd:boolean"/>
<Literal>true</Literal>
</Setting>
<Property key="ignoresAnnotations">
<Datatype
abbreviatedIRI="xsd:boolean"/>
<Literal>true</Literal>
</Property>
<Property key="ignoresDeclarations">
<Datatype
abbreviatedIRI="xsd:boolean"/>
<Literal>true</Literal>
</Property>
<Setting key="uniqueNameAssumption">
<Datatype
abbreviatedIRI="xsd:boolean"/>
<Literal>true</Literal>
</Setting>
<SupportedExtension identifier="&ole;retraction"/>
<SupportedExtension identifier="&ole;told"/>
<PublicKB kb="http://www.owllink.org/examples/KB_1"
name="Test KB
1"/>
<PublicKB kb="http://www.owllink.org/examples/KB_2"
name="Test KB
2"/>
</Description>
</ResponseMessage>
4.2 Creating Knowledge
Bases
The following sample request starts with a CreateKB request in order to allocate a new Knowledge
Base at the server. This is followed by a Tell request which asserts two subclass axioms to the
new KB. Finally a single ask request checks the satisfiability of
one of the classes introduced in one of the subclass axioms
(IsClassSatisfiable).
owllink-example-CreateKB-request-20091023.xml
<?xml version="1.0"
encoding="UTF-8"?>
<RequestMessage xmlns="http://www.owllink.org/owllink-xml#"
xmlns:owl="http://www.w3.org/2002/07/owl#"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.owllink.org/owllink-xml#
http://www.owllink.org/owllink-xml-20091023.xsd">
<CreateKB kb="http://www.owllink.org/examples/KB_1"/>
<Tell kb="http://www.owllink.org/examples/KB_1">
<owl:SubClassOf>
<owl:Class
IRI="A"/>
<owl:Class
IRI="B"/>
</owl:SubClassOf>
<owl:SubClassOf>
<owl:Class
IRI="B"/>
<owl:Class
IRI="C"/>
</owl:SubClassOf>
</Tell>
<IsClassSatisfiable kb="http://www.owllink.org/examples/KB_1">
<owl:Class IRI="A"/>
</IsClassSatisfiable>
<ReleaseKB kb="http://www.owllink.org/examples/KB_1"/>
</RequestMessage>
According to the [OWLlink Structural
Specification] every single Request must be acknowledged with a corresponding
Response considering the ordered sequence
of request elements. The CreateKB is
acknowledged by a KB element, the Tell
request is acknowledged by an OK response
and the satisfiability ask is acknowledged by a BooleanResponse carrying a positive answer.
owllink-example-CreateKB-response-20091023.xml
<?xml version="1.0"
encoding="UTF-8"?>
<ResponseMessage xmlns="http://www.owllink.org/owllink-xml#"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.owllink.org/owllink-xml#
http://www.owllink.org/owllink-xml-20091023.xsd">
<KB
kb="http://www.owllink.org/examples/KB_1"/>
<OK/>
<BooleanResponse result="true"/>
<OK/>
</ResponseMessage>
4.3 Retrieving Settings
The actual settings for a Knowledge Base can be retrieved by
sending a GetSettings message.
owllink-example-GetSettings-request-20091023.xml
<?xml version="1.0"
encoding="UTF-8"?>
<RequestMessage xmlns="http://www.owllink.org/owllink-xml#"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.owllink.org/owllink-xml#
http://www.owllink.org/owllink-xml-20091023.xsd">
<CreateKB kb="http://www.owllink.org/examples/KB_1"
name="KB
1"/>
<GetSettings kb="http://www.owllink.org/examples/KB_1"/>
<ReleaseKB kb="http://www.owllink.org/examples/KB_1"/>
</RequestMessage>
The corresponding ResponseMessage will contain all settings of the
specified Knowledge Base.
owllink-example-GetSettings-response-20091023.xml
<?xml version="1.0"
encoding="UTF-8"?>
<ResponseMessage xmlns="http://www.owllink.org/owllink-xml#"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.owllink.org/owllink-xml#
http://www.owllink.org/owllink-xml-20091023.xsd">
<KB
kb="http://www.owllink.org/examples/KB_1"/>
<Settings>
<Setting key="selectedProfile">
<OneOf
abbreviatedIRI="xsd:string">
<Literal>OWL
2 QL</Literal>
<Literal>OWL
2 RL</Literal>
</OneOf>
<Literal>OWL
2 RL</Literal>
</Setting>
<Setting key="abbreviatesIRIs">
<Datatype
abbreviatedIRI="xsd:boolean"/>
<Literal>false</Literal>
</Setting>
</Settings>
<OK/>
</ResponseMessage>
4.4 Changing Settings
Set allows to modify a KB setting. All
available settings as well as their default value can be inspected
using GetDescription as shown in Section 4.1 Introspecting Reasoner
Capabilities.
owllink-example-Set-request-20091023.xml
<?xml version="1.0"
encoding="UTF-8"?>
<RequestMessage xmlns="http://www.owllink.org/owllink-xml#"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.owllink.org/owllink-xml#
http://www.owllink.org/owllink-xml-20091023.xsd">
<CreateKB kb="http://www.owllink.org/examples/KB_1"
name="KB
1"/>
<Set
kb="http://www.owllink.org/examples/KB_1"
key="abbreviatesIRIs">
<Literal>true</Literal>
</Set>
<GetSettings kb="http://www.owllink.org/examples/KB_1"/>
<ReleaseKB kb="http://www.owllink.org/examples/KB_1"/>
</RequestMessage>
If the Set has not been refused an
OK will be returned, otherwise an
Error.
owllink-example-Set-response-20091023.xml
<?xml version="1.0"
encoding="UTF-8"?>
<ResponseMessage xmlns="http://www.owllink.org/owllink-xml#"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.owllink.org/owllink-xml#
http://www.owllink.org/owllink-xml-20091023.xsd">
<KB
kb="http://www.owllink.org/examples/KB_1"/>
<OK/>
<Settings>
<Setting key="selectedProfile">
<OneOf
abbreviatedIRI="xsd:string">
<Literal>OWL
2 QL</Literal>
<Literal>OWL
2 RL</Literal>
</OneOf>
<Literal>OWL
2 RL</Literal>
</Setting>
<Setting key="abbreviatesIRIs">
<Datatype
abbreviatedIRI="xsd:boolean"/>
<Literal>true</Literal>
</Setting>
</Settings>
<OK/>
</ResponseMessage>
4.5 Declaring Prefixes
CreateKB allows for declaring prefixes.
All abbreviated IRIs are then resolved with respect to the
prefixes.
owllink-example-Prefix-request-20091023.xml
<?xml version="1.0"
encoding="UTF-8"?>
<!DOCTYPE RequestMessage [
<!ENTITY ont "http://www.owllink.org/examples/myOntology#">
]>
<RequestMessage xmlns="http://www.owllink.org/owllink-xml#"
xml:base="http://www.owllink.org/examples/myOntology#"
xmlns:owl="http://www.w3.org/2002/07/owl#"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.owllink.org/owllink-xml#
http://www.owllink.org/owllink-xml-20091023.xsd">
<CreateKB kb="http://www.owllink.org/examples/KB_2">
<Prefix name="test" fullIRI="http://www.owllink.org/test/ont#"/>
<Prefix name="myOnt" fullIRI="http://www.owllink.org/examples/myOntology#"/>
</CreateKB>
<Tell kb="http://www.owllink.org/examples/KB_2">
<owl:SubClassOf>
<owl:Class
abbreviatedIRI="test:A"/>
<owl:Class
abbreviatedIRI="myOnt:A"/>
</owl:SubClassOf>
</Tell>
<Set
kb="http://www.owllink.org/examples/KB_2"
key="abbreviatesIRIs">
<Literal>false</Literal>
</Set>
<GetSubClasses kb="http://www.owllink.org/examples/KB_2"
direct="false">
<owl:Class IRI="&ont;A"/>
</GetSubClasses>
<GetSubClasses kb="http://www.owllink.org/examples/KB_2"
direct="false">
<owl:Class abbreviatedIRI="myOnt:A"/>
</GetSubClasses>
<Set
kb="http://www.owllink.org/examples/KB_2"
key="abbreviatesIRIs">
<Literal>true</Literal>
</Set>
<GetSubClasses kb="http://www.owllink.org/examples/KB_2"
direct="false">
<owl:Class IRI="http://www.owllink.org/examples/myOntology#A"/>
</GetSubClasses>
<GetSubClasses kb="http://www.owllink.org/examples/KB_2"
direct="false">
<owl:Class IRI="A"/>
</GetSubClasses>
<ReleaseKB kb="http://www.owllink.org/examples/KB_2"/>
</RequestMessage>
If the CreateKB and the Tell are processed successfully the corresponding
ResponseMessage will contain a
KB and a OK
response.
owllink-example-Prefix-response-20091023.xml
<?xml version="1.0"
encoding="UTF-8"?>
<ResponseMessage xmlns="http://www.owllink.org/owllink-xml#"
xmlns:owl="http://www.w3.org/2002/07/owl#"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.owllink.org/owllink-xml#
http://www.owllink.org/owllink-xml-20091023.xsd">
<KB
kb="http://www.owllink.org/examples/KB_2"/>
<OK/>
<OK/>
<SetOfClassSynsets>
<ClassSynset>
<owl:Class
IRI="http://www.owllink.org/test/ont#A"/>
</ClassSynset>
</SetOfClassSynsets>
<SetOfClassSynsets>
<ClassSynset>
<owl:Class
IRI="http://www.owllink.org/test/ont#A"/>
</ClassSynset>
</SetOfClassSynsets>
<OK/>
<SetOfClassSynsets>
<ClassSynset>
<owl:Class
abbreviatedIRI="test:A"/>
</ClassSynset>
</SetOfClassSynsets>
<SetOfClassSynsets>
<ClassSynset>
<owl:Class
abbreviatedIRI="test:A"/>
</ClassSynset>
</SetOfClassSynsets>
<OK/>
</ResponseMessage>
4.6 Loading Ontologies
The following example demonstrates that it is possible to create a
Knowledge Base and fill it with both (i) axioms of ontologies
loaded directly from their location and (ii) directly transmitted
axioms. Note that the prefix declared for the Knowledge Base are
not considered when executing the LoadOntologies request.
owllink-example-LoadOntologies-request-20091023.xml
<?xml version="1.0"
encoding="UTF-8"?>
<RequestMessage xmlns="http://www.owllink.org/owllink-xml#"
xmlns:owl="http://www.w3.org/2002/07/owl#"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.owllink.org/owllink-xml#
http://www.owllink.org/owllink-xml-20091023.xsd">
<CreateKB kb="http://www.owllink.org/examples/KB_1">
<Prefix name="test:" fullIRI="http://www.owllink.org/test/ont#"/>
<Prefix name="myOnt:" fullIRI="http://www.owllink.org/examples/myOntology#"/>
</CreateKB>
<LoadOntologies kb="http://www.owllink.org/examples/KB_1">
<OntologyIRI IRI="http://www.owllink.org/examples/ontologies/myOntology"/>
<OntologyIRI IRI="http://www.owllink.org/examples/ontologies/myOntology2"/>
<IRIMapping key="http://www.owlllink.org/examples/ontologies/myOntology"
value="file:///examples/ontologies/myOntology"/>
</LoadOntologies>
<Tell kb="http://www.owllink.org/examples/KB_1">
<owl:SubClassOf>
<owl:Class
abbreviatedIRI="test:A"/>
<owl:Class
abbreviatedIRI="myOnt:A"/>
</owl:SubClassOf>
</Tell>
<ReleaseKB kb="http://www.owllink.org/examples/KB_1"/>
</RequestMessage>
The corresponding response message contains a KB response as well as OK
messages indicating that the LoadOntologies
respectively Tell requests have been
successfully processed by the server.
owllink-example-LoadOntologies-request-20091023.xml
<?xml version="1.0"
encoding="UTF-8"?>
<ResponseMessage xmlns="http://www.owllink.org/owllink-xml#"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.owllink.org/owllink-xml#
http://www.owllink.org/owllink-xml-20091023.xsd">
<KB
kb="http://www.owllink.org/examples/KB_1"/>
<OK/>
<OK/>
<OK/>
</ResponseMessage>
4.7 Pooling Requests
The following example demonstrates that it is possible to pool tell
and ask operations for different Knowledge Bases within one
RequestMessage. This is useful, say for
test-suites or benchmarking. The following request creates the a
first KB, adds OWL axioms, poses queries, and then one creates a
second one. Note that the next to last request will release only
the first Knowledge Base: for that, the last ask will produce an
error because the KB it is referring to is no longer available.
owllink-example-PoolingRequests-request-20091023.xml
<?xml version="1.0"
encoding="UTF-8"?>
<RequestMessage xmlns="http://www.owllink.org/owllink-xml#"
xmlns:owl="http://www.w3.org/2002/07/owl#"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.owllink.org/owllink-xml#
http://www.owllink.org/owllink-xml-20091023.xsd">
<CreateKB kb="KB_1"/>
<!-- Some
tells in KB_1 -->
<Tell kb="KB_1">
<owl:SubClassOf>
<owl:Class
IRI="B"/>
<owl:Class
IRI="A"/>
</owl:SubClassOf>
<owl:SubClassOf>
<owl:Class
IRI="C"/>
<owl:Class
IRI="A"/>
</owl:SubClassOf>
<owl:EquivalentClasses>
<owl:Class
IRI="D"/>
<owl:Class
IRI="E"/>
</owl:EquivalentClasses>
<owl:ClassAssertion>
<owl:Class
IRI="A"/>
<owl:NamedIndividual
IRI="iA"/>
</owl:ClassAssertion>
<owl:SubClassOf>
<owl:Class
IRI="C"/>
<owl:Class
IRI="A"/>
</owl:SubClassOf>
</Tell>
<!-- Some
asks -->
<GetAllClasses kb="KB_1"/>
<GetEquivalentClasses kb="KB_1">
<owl:Class IRI="D"/>
</GetEquivalentClasses>
<IsClassSubsumedBy kb="KB_1">
<owl:Class abbreviatedIRI="owl:Thing"/>
<owl:Class abbreviatedIRI="owl:Nothing"/>
</IsClassSubsumedBy>
<GetSubClasses kb="KB_1">
<owl:Class IRI="C"/>
</GetSubClasses>
<!-- Some
tells for the public KB named 'MyKB_2' -->
<CreateKB kb="KB_2"
name="MyKB_2"/>
<Tell kb="KB_2">
<owl:SubClassOf>
<owl:Class
IRI="A"/>
<owl:Class
IRI="B"/>
</owl:SubClassOf>
</Tell>
<!-- KB
Management -->
<ReleaseKB kb="KB_2"/>
<ReleaseKB kb="KB_1"/>
<!-- One
more ask -->
<GetAllClasses kb="KB_1"/>
</RequestMessage>
Note that the request message contains a repetition of an axiom and
therefore the OWLlink server acknowledges the Tell with a warning. The response to the last request
has to be an Error because KB_1
has been released before.
owllink-example-PoolingRequests-response-20091023.xml
<?xml version="1.0"
encoding="UTF-8"?>
<ResponseMessage xmlns="http://www.owllink.org/owllink-xml#"
xmlns:owl="http://www.w3.org/2002/07/owl#"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.owllink.org/owllink-xml#
http://www.owllink.org/owllink-xml-20091023.xsd">
<KB
kb="KB_1"/>
<OK
warning="Duplicate
axiom ignored"/>
<SetOfClasses>
<owl:Class IRI="A"/>
<owl:Class IRI="B"/>
<owl:Class IRI="C"/>
<owl:Class IRI="D"/>
<owl:Class IRI="E"/>
</SetOfClasses>
<SetOfClasses>
<owl:Class IRI="D"/>
<owl:Class IRI="E"/>
</SetOfClasses>
<BooleanResponse result="false"/>
<SetOfClassSynsets/>
<KB
kb="KB_2"/>
<OK/>
<OK/>
<OK/>
<KBError error="KB_1 does
not exist!"/>
</ResponseMessage>
4.8 Retrieving Taxonomies
The following example shows how to retrieve the class-subsumption
hierarchy of a KB. In this example four Knowledge Bases are creates
and the class-subsumption hierarchy is requested for each of them.
Note that these four KBs correspond to the example KB introduced in
Section '5.3.2 Retrieving the Class Hierarchy' [OWLlink Structural
Specification]
owllink-example-Taxonomy-request-20091023.xml
<?xml version="1.0"
encoding="UTF-8"?>
<RequestMessage xmlns="http://www.owllink.org/owllink-xml#"
xmlns:owl="http://www.w3.org/2002/07/owl#"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.owllink.org/owllink-xml#
http://www.owllink.org/owllink-xml-20091023.xsd">
<CreateKB kb="KB_1"/>
<CreateKB kb="KB_2"/>
<Tell kb="KB_2">
<owl:SubClassOf>
<owl:Class
IRI="A"/>
<owl:Class
abbreviatedIRI="owl:Thing"/>
</owl:SubClassOf>
</Tell>
<CreateKB kb="KB_3"/>
<Tell kb="KB_3">
<owl:SubClassOf>
<owl:Class
IRI="A"/>
<owl:Class
abbreviatedIRI="owl:Thing"/>
</owl:SubClassOf>
<owl:SubClassOf>
<owl:Class
IRI="B"/>
<owl:Class
IRI="A"/>
</owl:SubClassOf>
<owl:SubClassOf>
<owl:Class
IRI="D"/>
<owl:Class
IRI="A"/>
</owl:SubClassOf>
</Tell>
<CreateKB kb="KB_4"/>
<Tell kb="KB_4">
<owl:EquivalentClasses>
<owl:Class
IRI="A"/>
<owl:Class
abbreviatedIRI="owl:Thing"/>
</owl:EquivalentClasses>
<owl:EquivalentClasses>
<owl:Class
IRI="C"/>
<owl:Class
abbreviatedIRI="owl:Nothing"/>
</owl:EquivalentClasses>
<owl:SubClassOf>
<owl:Class
IRI="B"/>
<owl:Class
abbreviatedIRI="owl:Thing"/>
</owl:SubClassOf>
</Tell>
<GetSubClassHierarchy kb="KB_1"/>
<GetSubClassHierarchy kb="KB_2"/>
<GetSubClassHierarchy kb="KB_3"/>
<GetSubClassHierarchy kb="KB_4"/>
<ReleaseKB kb="KB_1"/>
<ReleaseKB kb="KB_2"/>
<ReleaseKB kb="KB_3"/>
<ReleaseKB kb="KB_4"/>
</RequestMessage>
The corresponding response message contains responses for the
management requests as well as the GetSubClassHierarchy request.
owllink-example-Taxonomy-response-20091023.xml
<?xml version="1.0"
encoding="UTF-8"?>
<ResponseMessage xmlns="http://www.owllink.org/owllink-xml#"
xmlns:owl="http://www.w3.org/2002/07/owl#"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.owllink.org/owllink-xml#
http://www.owllink.org/owllink-xml-20091023.xsd">
<KB
kb="KB_1"/>
<KB
kb="KB_2"/>
<OK/>
<KB
kb="KB_3"/>
<OK/>
<KB
kb="KB_4"/>
<OK/>
<ClassHierarchy>
<ClassSubClassesPair>
<ClassSynset>
<owl:Class
abbreviatedIRI="owl:Thing"/>
</ClassSynset>
<SetOfClassSynsets/>
</ClassSubClassesPair>
</ClassHierarchy>
<ClassHierarchy>
<ClassSubClassesPair>
<ClassSynset>
<owl:Class
abbreviatedIRI="owl:Thing"/>
</ClassSynset>
<SetOfClassSynsets>
<ClassSynset>
<owl:Class
IRI="A"/>
</ClassSynset>
</SetOfClassSynsets>
</ClassSubClassesPair>
</ClassHierarchy>
<ClassHierarchy>
<ClassSubClassesPair>
<ClassSynset>
<owl:Class
abbreviatedIRI="owl:Thing"/>
</ClassSynset>
<SetOfClassSynsets>
<ClassSynset>
<owl:Class
IRI="A"/>
</ClassSynset>
</SetOfClassSynsets>
</ClassSubClassesPair>
<ClassSubClassesPair>
<ClassSynset>
<owl:Class
IRI="A"/>
</ClassSynset>
<SetOfClassSynsets>
<ClassSynset>
<owl:Class
IRI="B"/>
</ClassSynset>
<ClassSynset>
<owl:Class
IRI="D"/>
</ClassSynset>
</SetOfClassSynsets>
</ClassSubClassesPair>
</ClassHierarchy>
<ClassHierarchy>
<ClassSubClassesPair>
<ClassSynset>
<owl:Class
IRI="A"/>
<owl:Class
abbreviatedIRI="owl:Thing"/>
</ClassSynset>
<SetOfClassSynsets>
<ClassSynset>
<owl:Class
IRI="B"/>
</ClassSynset>
</SetOfClassSynsets>
</ClassSubClassesPair>
<ClassSubClassesPair>
<ClassSynset>
<owl:Class
IRI="B"/>
</ClassSynset>
<SetOfClassSynsets>
<ClassSynset>
<owl:Class
IRI="C"/>
<owl:Class
abbreviatedIRI="owl:Nothing"/>
</ClassSynset>
</SetOfClassSynsets>
</ClassSubClassesPair>
</ClassHierarchy>
<OK/>
<OK/>
<OK/>
<OK/>
</ResponseMessage>
5. References
- [DIG 1.1]
- The DIG
Description Logic Interface: DIG/1.1. Sean Bechhofer.
Technical Report, Feb 2003, http://dl-web.man.ac.uk/dig/2003/02/interface.pdf.
- [EXI]
- Efficient XML Interchange Format
1.0 John Schneider and Takuki Kamiya. W3C Working Draft,
March 2008.
- [HTTP/1.1]
- Hypertext Transfer
Protocol - HTTP/1.1, Request for Comments 2616. R.
Fielding, J. Gettys, J. Mogul, H. Frystyk, L. Masinter, P. Leach,
and T. Berners-Lee.
- [OWL 2 XML Serialization]
- OWL 2 Web Ontology Language: XML Serialization Boris Motik, Bijan Parsia, Peter F. Patel-Schneider, eds. W3C Recommendation, 27 October 2009, http://www.w3.org/TR/2009/REC-owl2-xml-serialization-20091027/. Latest version available at http://www.w3.org/TR/owl2-xml-serialization/.
- [OWLlink Structural Specification]
- OWLlink: Structural Specification Thorsten Liebig, Marko Luther, Olaf Noppens, Michael Wessel. Working Group Recommendation, 23 October 2009, http://www.owllink.org/owllink-20091023/. Latest version available at http://www.owllink.org/owllink/.
- [SOAP]
- SOAP Version
1.2 Part 1: Messaging Framework (Second Edition). M.
Gudgin, M. Hadley, N. Mendelsohn, J-J. Moreau, H. F. Nielsen, A.
Karmarkar, Y. Lafon, eds. W3C Recommendation 27 April 2007,
http://www.w3.org/TR/2007/REC-soap12-part1-20070427/.
- [XML Schema]
- XML Schema
Part 1: Structures Second Edition. Henry S. Thompson,
David Beech, Murray Maloney, Noah Mendelsohn, eds. W3C
Recommendation 28 October 2004, http://www.w3.org/TR/2004/REC-xmlschema-1-20041028/.