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A Semantic Web Content Model and Repository
Max Völkel
6.9.2007I-Semantics,
Graz
© 2007 Max [email protected]
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Outline
Motivation
Analysis: Web vs. Semantic Web
Developing a unified Semantic Web Content Model In three easy steps
Implementation
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How to model structure + content in one model?
Background Wikis, Personal Semantic Wikis, Semantic Desktop, …
Two motivations: Bring flexibility and expressivity of RDF to the end-user Allow RDF to model and represent content as well – not only its
metadata
Goal: Unified Model As usable as the web
But how to represent semantics? Semantic queries? As expressive and as flexible as the semantic web
How to represent binary data (desktop files, web resources) in RDF?
Unified search “Give me all papers written by author X which contain Y”
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Analysis: The Web
Granularity: Gets smaller Web 1.0: homepages, portals Web 2.0: micro-content
Renderable representations
Freedom of formalisation Less semantic HTML is less
portable, but works
HTTP
HTTPHTML,
JPG, CSS, JS, PDF, …
Content
Representation
URI
ChangeDate
MimeType
Encoding
meta-data
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Analysis: The Semantic Web
Flexible, very expressive
Not expressive enough: Literals cannot be addressed Statements cannot be addressed (but
reified)
10 different node types complex for end-users
Exising formal knowledge can be re-used
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Content granularity
Expressivity
Binary Content
Freedom of formalisation
Human-usable Renderable representations Human-type- and memorizable names (e.g. like WikiWords) Inverse Relations
Knowledge re-use
Standard CMS features: Access rights addressable parts Versioning addressable parts
Requirements for a SWCM
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Feature Web Sem. WebDesired
Content granularity mid/large small any Goal: From small comments to full web pages/files
Expressivity - + ++
Binary Content ++ ~ ++
Freedom of formalisation + - +
Human-usable ++ - ++ Renderable representations Human-type- and memorizable names (e.g. like WikiWords) Inverse Relations
Knowledge re-use - ++ +
Standard CMS features: Access rights addressable parts + ~
+ Versioning addressable parts + ~
+
Comparison
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Creating the SWCM:
Step 1: A Human-Usable RDF
1
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Step 1: A Human-Usable RDF
Items have a URI and can have a Literal Addressable Literals
Item0..1
URI Literal
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Step 1: A Human-Usable RDF
Statements connect Items Expressivity of RDF
Item
Statement
source
targ
et
0..1
URI
relation
Literal
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Step 1: A Human-Usable RDF
Addressable Statements Syntactic sugar over reification
Item
Statement
source
targ
et
0..1
URI
relation
Literal
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Step 1: A Human-Usable RDF
Address Items via human-type-able name (e.g. WikiWords) Human-usable naming
Item
Statement NameItem
source
targ
et
0..1
URI
relation
Literal
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Step 1: A Human-Usable RDF
Statements (Item, NameItem, Item) Decision that relations should be human-name-able
Item
Statement NameItem
source
targ
et
0..1
URI
relation
Literal
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Step 1: A Human-Usable RDF
Relations have always an inverse Item-centric rendering easier for tools
Item
Statement
Relation
NameItem
source
targ
et
inverse
0..1
URI
relation
Literal
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Step 1: A Human-Usable RDF
A Model contains Items
A Model has a URI
Item
Model
Statement
Relation
NameItem
source
targ
et
inverse
0..1
URI0..n
relation
Literal
© 2007 Max [email protected]
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Creating the SWCM:
Step 2: Include Binary Content
2
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Step 2: Include Binary Content
From addressable literals to addressable representations
Literal
Item0..1
URI
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Step 2: Include Binary Content
Representation
Item0..1
URI
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Step 2: Include Binary Content
Representations on the web have some built-in properties Metadata: Mime-type, encoding, change-date Data: the actual content itself
Representation
Item0..1
URI
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Step 2: Include Binary Content
Content
Representation
ChangeDate
MimeType
Encoding
Item0..1
URI
Representations on the web have some built-in properties Metadata: Mime-type, encoding, change-date Data: the actual content itself
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Step 2: Include Binary Content
In SWCM, representations have an author Like in wikis, blogs, web pages, … Can be „anonymous“
Content
Representation
ChangeDate
MimeType
Encoding
Item0..1
URI
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Step 2: Include Binary Content
In SWCM, representations have an author Like in wikis, blogs, web pages, … Can be „anonymous“
author
Content
Representation
ChangeDate
MimeType
Encoding
Item0..1
URI
© 2007 Max [email protected]
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Creating the SWCM:
Step 3: Merge Step 1 and Step 2
3
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The Semantic Web Content Model
author
Content
Representation
ChangeDate
MimeType
Encoding
Item
Model
Statement
Relation
NameItem
source
targ
et
inverse
0..1
URI0..n
relation
Structure Content
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The Semantic Web Content Model
We expect end-users to understand the circled parts
author
Content
Representation
ChangeDate
MimeType
Encoding
Item
Model
Statement
Relation
NameItem
source
targ
et
inverse
0..1
URI0..n
relation
Structure Content
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Swecr is implemented in two layers
swecr.core interface
swecr.model interface
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The swecr.model API (see www.swecr.org)
IItemINameContent
IModel
IStatement
IContent
IRelaton
INameItem
source
targ
et
inverse
0..1
IMimeTypeRDF2Go.URI
0..n
IRepository 0..n
author
1. Content of a INameItem is unique within its
IModel.2. Mimetype always =
„text/plain“
ChangeDate
IContentItem
IBinContent
www.swecr.org
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Swecr.core: Some Content stored in RDF
:FZI a swcm:NameItem , swcm:Item ;swcm:hasChangeDate "2007-08-24T16:07:29Z"^^xsd:dateTime ;swcm:hasContent “FZI Forschungszentrum Informatik" .
:employs a swcm:NameItem , swcm:Item , swcm:Relation ;swcm:hasAuthor swcm:anonymous-author ;swcm:hasChangeDate "2007-08-24T16:07:32Z"^^xsd:dateTime ;swcm:hasContent “employs" ;swcm:hasInverse :employedBy .
:worksFor a swcm:NameItem , swcm:Item , swcm:Relation ;swcm:hasAuthor swcm:anonymous-author ;swcm:hasChangeDate "2007-08-24T16:07:33Z"^^xsd:dateTime ;swcm:hasContent “works for" ;swcm:hasInverse :employs .
www.swecr.org
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Implemented in two layers
<urn:rnd:-1d72b0a2:11498a0d25f:-7fff>a swcm:Item , swcm:Statement ;swcm:hasChangeDate "2007-08-24T16:07:30Z"^^xsd:dateTime ;swcm:stmtRelation :employs ;swcm:stmtSource :FZI ;swcm:stmtTarget :Max .
www.swecr.org
Statements stored in two RDF models: user model
and index model Query answering
:FZI :employs :Max .
:Max :worksFor :FZI .redundant
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But where to store binaries?
?RDF ModelSet
ModelSetImpl
swecr.core interface
swecr.model interface
user model index model
www.swecr.org
© 2007 Max [email protected]
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BinStore – a simple binary store
Intuition: The simplest web-like API, that would possibly work (and allow random-access)
Data model:URI Metadata + InputStream /
OutputStream
Simple implementation on files Future: Consider JCR
www.swecr.org
getReadHandle InputStream readStream(); getMimeType(), getSize()
getWriteHandle writeStream( InputStream,
MimeType ) setMimeType( MimeType )
getRandomAccessHandle
delete( URI )
Binary Store
BinStoreImpl
API
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Persistence in an RDF ModelSet and a Binary Store
Binary Store
RDF ModelSet
ModelSetImpl
BinStoreImpl
swecr.core interface
swecr.model interface
www.swecr.org
user model index model
Full text queries need a full text index
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The complete swecr.core
www.swecr.org
Binary Store
RDF ModelSet
Query Engine
IndexingBinStore
IndexingModelSet
BinStoreImpl
TextIndexImpl
ModelSetImpl
AdapterServer
Bin2Text(Aperture
)
swecr.core interface
swecr.model interface
Existing component In progress Download from www.swecr.org
© 2007 Max [email protected]
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Example: Wiki-page
Example: A wiki-page in SWCM Title of wiki page NameItem Content of wiki page Item Relation between title and page content Statement
Who uses it? WavesWiki (part of BMBF project, http://waves.fzi.de) SemFS a Semantic File System (presented at I-KNOW in 2006) Conceptual Data Structures (end-user personal KM tool) Interest from XWiki and Cognium Systems
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Summary
SWCM is a content management model combining the usability of the web with the expressivity and flexibility of the semantic web
Item
Statement
Relation
NameItem
source
targ
et
inverse
relationFuture Work:
Refactor core layer into smaller parts (services)
Create RDF with binaries – API
Unified queries (like the LuceneSAIL or LARQ)
Crawling of external resources (index localled, stored remote)
From structured text to SWCM models (see paper)
Thank You.
