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Developer training session providing an overview of the core features and services of the Talis Platform. Includes basic overview of REST and RDF
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Getting Started with the Talis PlatformLeigh Dodds
Platform Programme Manager
Talis
December 2008
http://creativecommons.org/licenses/by/2.0/uk/
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Agenda
• Platform Overview• Core Concepts• Review of the RDF Model• Managing binary data• Managing structured metadata• Exploring RDF data with SPARQL• Extra Features• Store Administration• Summary
Platform Overview
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Software as a Service
Multi-Tenant Data Storage Service
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Unstructured Data Storage
e.g. binary files, including images, documents, etc
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Structured Data Storage
RDF metadata
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Access Control
All data is open (to read) by defaultConfigurable access options
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Full-Text Searching and Querying
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Standards Compliance
RDF, SPARQL, HTTP
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Platform Architecture
Web API
Metabox
Contentbox
REST, RDFAuthentication & AuthorizationContent Negotiation
Core Conceptsaka “The Science Bit”
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REST
Representational State Transfer
Correct Use of HTTP
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Resource-Centric API
Everything has a unique URI
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Interact with resources using HTTP
GET = readPUT = write
POST = update/modifyDELETE = delete
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Use HTTP Response Codes
200 = OK201 = Created (new resource)
202 = Accepted (for processing)400 = Bad Request500 = Server Error
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Mime Types
Used to identifiy content & meaning of request and response body
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Content Negotiation
Majority of services support multiple output options, list varies by resource
Accept headeroutput parameter
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Our Service Checklist
Consistent URI structureEvery service has human interfacePlain text error messages for easy debuggingCacheable…etc
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Authentication
HTTP Digest Authentication
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Authentication Example
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Authorization
By default stores are world-readable, Store owner writable
Customisable roles and privileges per-Store
Review of the RDF Model
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Apollo 11 was launched from Cape Canaveral
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Apollo 11 was launched from Cape Canaveral
Subject Predicate Object
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<http://purl.org/net/schemas/space/spacecraft/apollo-11> <http://purl.org/net/schemas/space/launchsite>
<http://purl.org/net/schemas/space/launchsite/capecanaveral>.
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space:spacecraft/apollo-11 space:launchsite
space:launchsite/capecanaveral.
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space:spacecraft/apollo-11 space:launchsite space:launchsite/capecanaveral.
space:spacecraft/apollo-11 rdfs:label “Apollo 11”.
space:launchsite/capecanaveral rdfs:label “Cape Canaveral”.
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Benefits of RDF?
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Good for Semi-structured Data
“Schema-Free”Very Flexible
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Extensible
New propertiesNew resources
New types of resourceNew statements
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Encourages Convergence
Reuse of vocabularies (i.e. properties)Reuse of identifiers (i.e. talk about the same things)
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Simplifies Data Integration and Aggregation
Shared identifiersCommon data model
Common query languageCommon data formats
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Several Different Ways to Serialize RDF
Optimized for different purposes
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Turtle
Simple to read and hand-authorUsed in SPARQL query language
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@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>@prefix space: <http://purl.org/net/schemas/space/> @@prefix dc: <http://purl.org/dc/elements/1.1/>
<http://purl.org/net/schemas/space/spacecraft/1969-059A> rdf:type
<http://purl.org/net/schemas/space/Spacecraft>; dc:description "Apollo 11 was…”; space:agency "United States" .
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RDF/XML
Best for data interchangeHarder to read
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<rdf:RDF xmlns:j.0="http://xmlns.com/foaf/0.1/“ xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:space="http://purl.org/net/schemas/space/" xmlns:dc="http://purl.org/dc/elements/1.1/" xml:base="http://purl.org/net/schemas/space">
<rdf:Description rdf:about="/spacecraft/1969-059A">
<dc:description>Apollo 11 was…</dc:description> <rdf:type rdf:resource="http://purl.org/net/schemas/space/Spacecraft"/> <space:agency>United States</space:agency>
</rdf:Description>
</rdf:RDF>
The Content BoxManaging unstructured, binary data
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Store any stream of binary data
Images, documents, Javascript, etc
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Full HTTP Caching Support
ETagsEfficient retrieval
Conditional updates
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Server or Client Assignment of Identifiers
Provides full control over how URIs assigned
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ContentBox URLs
• /storename/items– The Contentbox container
• /storename/items/<id>– An individual item
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Adding Content
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Deleting Content
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Metadata for Contentbox Resources
Minimum is URI and ETagExtract height & width of images
…more metadata extraction in future
The Meta Box
Managing structured metadata
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Full RDF Data Storage
Create, read, update, delete RDF resourcesQuery RDF data
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Configurable Full Text Indexing of RDF
Indexes updated whenever new metadata added
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Versioned and Un-Versioned Updates
By submitting data to separate resourcesMaintain audit trail
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Can be Divided into Sub-Graphs
Separate access control options
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Metabox URLs
• /storename/meta– The metabox
• /storename/meta/changesets– The collection of changesets associated with this metabox
• /storename/meta/graphs – The collection of sub-graphs
• /storename/meta/graphs/{id}– A sub-graph
• /storename/meta/graphs/{id}/changesets – The collection of changesets associated with a sub-graph
• /storename/services/sparql– SPARQL endpoint for metabox
• /storename/services/multisparql– SPARQL endpoint for querying across all sub-graphs
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Storing RDF
POST application/rdf+xmlChanges saved immediately
Search indexing asynchronous
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Triples are Merged into Store
Can catch out the unwaryUpdates happen through separate mechanism
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Retrieving Metadata
/meta?about=…URI…Can select RDF serialization
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Updating Resources
POST application/vnd.talis.changeset+xml
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ChangeSets
Vocabulary that specifies removals/additions to an RDF graph
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:cs="http://purl.org/vocab/changeset/schema#"> <cs:ChangeSet rdf:about="http://example.com/changesets#change"> <cs:subjectOfChange rdf:resource="http://purl.org/net/schema/space/launch/1969-059"/> <cs:createdDate>2008-12-08T00:00:00Z</cs:createdDate> <cs:creatorName>Leigh Dodds</cs:creatorName> <cs:changeReason>More accurate launch time</cs:changeReason> <cs:removal> <rdf:Statement> <rdf:subject rdf:resource="http://purl.org/net/schema/space/launch/1969-
059"/> <rdf:predicate rdf:resource="http://purl.org/net/schema/space/launched"/> <rdf:object>1969-07-16</rdf:object> </rdf:Statement> </cs:removal> <cs:addition> <rdf:Statement> <rdf:subject rdf:resource="http://purl.org/net/schema/space/launch/1969-
059"/> <rdf:predicate rdf:resource="http://purl.org/net/schema/space/launched"/> <rdf:object>1969-07-16T13:32:00</rdf:object> </rdf:Statement> </cs:addition> </cs:ChangeSet></rdf:RDF>
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:cs="http://purl.org/vocab/changeset/schema#"> <cs:ChangeSet rdf:about="http://example.com/changesets#change"> <cs:subjectOfChange rdf:resource="http://purl.org/net/schema/space/launch/1969-059"/> <cs:createdDate>2008-12-08T00:00:00Z</cs:createdDate> <cs:creatorName>Leigh Dodds</cs:creatorName> <cs:changeReason>More accurate launch time</cs:changeReason> <cs:removal> <rdf:Statement> <rdf:subject rdf:resource="http://purl.org/net/schema/space/launch/1969-
059"/> <rdf:predicate
rdf:resource="http://purl.org/net/schema/space/launched"/> <rdf:object>1969-07-16</rdf:object> </rdf:Statement> </cs:removal> <cs:addition> <rdf:Statement> <rdf:subject rdf:resource="http://purl.org/net/schema/space/launch/1969-
059"/> <rdf:predicate rdf:resource="http://purl.org/net/schema/space/launched"/> <rdf:object>1969-07-16T13:32:00</rdf:object> </rdf:Statement> </cs:addition> </cs:ChangeSet></rdf:RDF>
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:cs="http://purl.org/vocab/changeset/schema#"> <cs:ChangeSet rdf:about="http://example.com/changesets#change"> <cs:subjectOfChange rdf:resource="http://purl.org/net/schema/space/launch/1969-059"/> <cs:createdDate>2008-12-08T00:00:00Z</cs:createdDate> <cs:creatorName>Leigh Dodds</cs:creatorName> <cs:changeReason>More accurate launch time</cs:changeReason> <cs:removal> <rdf:Statement> <rdf:subject rdf:resource="http://purl.org/net/schema/space/launch/1969-
059"/> <rdf:predicate rdf:resource="http://purl.org/net/schema/space/launched"/> <rdf:object>1969-07-16</rdf:object> </rdf:Statement> </cs:removal> <cs:addition> <rdf:Statement> <rdf:subject rdf:resource="http://purl.org/net/schema/space/launch/1969-
059"/> <rdf:predicate
rdf:resource="http://purl.org/net/schema/space/launched"/> <rdf:object>1969-07-16T13:32:00</rdf:object> </rdf:Statement> </cs:addition> </cs:ChangeSet></rdf:RDF>
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Versioned Updates
POST to /meta/changesetsApply update and stores changeset for later retrieval
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Batch Updates
Combine several changesets into single POSTLinked together to define ordering
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:cs="http://purl.org/vocab/changeset/schema#"> <cs:ChangeSet rdf:about="http://example.com/changesets/1"> <cs:subjectOfChange
rdf:resource="http://purl.org/net/schema/space/launch/1969-059"/>
<cs:changeReason>More accurate launch time</cs:changeReason> <cs:precedingChangeset rdf:resource="http://example.com/changesets/2"/> <!– changes --> </cs:ChangeSet> <cs:ChangeSet rdf:about="http://example.com/changesets/2"> <cs:subjectOfChange
rdf:resource="http://purl.org/net/schema/space/launch/1969-059"/>
<cs:precedingChangeset rdf:resource="http://example.com/changesets/3"/>
<!– changes --> </cs:ChangeSet> <cs:ChangeSet rdf:about="http://example.com/changesets/3"> <cs:subjectOfChange
rdf:resource="http://purl.org/net/schema/space/spacecraft/1969-059D"/> <!– changes -->... </cs:ChangeSet> </rdf:RDF>
Data Extraction & Exploration with SPARQL
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SPARQL
RDF query language; HTTP protocol; Results format4 different forms of query
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ASK
Test whether the graph contains some data of interest
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#Was there a launch on 16th July 1969?
PREFIX space: <http://purl.org/net/schemas/space/>PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
ASK WHERE { ?launch space:launched "1969-07-16"^^xsd:date.}
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<?xml version="1.0"?><sparql xmlns="http://www.w3.org/2005/sparql-results#"> <head> </head> <boolean>true</boolean></sparql>
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DESCRIBE
Generate an RDF description of a resource(s)
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#Describe launch(es) that occurred on 16th July 1969
PREFIX space: <http://purl.org/net/schemas/space/>PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
DESCRIBE ?launch WHERE { ?launch space:launched "1969-07-16"^^xsd:date.}
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#Describe spacecraft launched on 16th July 1969
PREFIX space: <http://purl.org/net/schemas/space/>PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
DESCRIBE ?spacecraft WHERE {
?launch space:launched "1969-07-16"^^xsd:date.
?spacecraft space:launch ?launch.
}
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CONSTRUCT
Create a custom RDF graph based on query criteria
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PREFIX space: <http://purl.org/net/schemas/space/>PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>PREFIX foaf: <http://xmlns.com/foaf/0.1/>
CONSTRUCT { ?spacecraft foaf:name ?name; space:agency ?agency; space:mass ?mass. }WHERE { ?launch space:launched "1969-07-16"^^xsd:date.
?spacecraft space:launch ?launch; foaf:name ?name; space:agency ?agency; space:mass ?mass. }
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SELECT
SQL style result set retrieval
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PREFIX space: <http://purl.org/net/schemas/space/>PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?name ?agency ?massWHERE {
?launch space:launched "1969-07-16"^^xsd:date.
?spacecraft space:launch ?launch; foaf:name ?name; space:agency ?agency; space:mass ?mass. }
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<?xml version="1.0"?><sparql xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns="http://www.w3.org/2005/sparql-results#" > <head> <variable name="name"/> <variable name="agency"/> <variable name="mass"/> </head> <results> <result> <binding name="name"> <literal>Apollo 11 Command and Service Module (CSM)</literal> </binding> <binding name="agency"> <literal>United States</literal> </binding> <binding name="mass"> <literal>28801.0</literal> </binding> </result> <!– more results --> </results></sparql>
…as XML
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{ "head": { "vars": [ "name" , "agency" , "mass" ] } , "results": { "bindings": [ { "name": { "type": "literal" , "value": "Apollo 11 Command and Service Module (CSM)" } , "agency": { "type": "literal" , "value": "United States" } , "mass": { "type": "literal" , "value": "28801.0" } } , { "name": { "type": "literal" , "value": "Apollo 11 SIVB" } , "agency": { "type": "literal" , "value": "United States" } , "mass": { "type": "literal" , "value": "13300.0" } } , { "name": { "type": "literal" , "value": "Apollo 11 Lunar Module / EASEP" } , "agency": { "type": "literal" , "value": "United States" } , "mass": { "type": "literal" , "value": "15065.0" } } ] }}
…as JSON
Tour of Extra Features
Searching, browsing, augmentation
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Searching
Full text index over RDF literalsConfigurable indexing options
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/items?query=[query] &max=[10] &offset=[0] &sort=[comma-separated fieldnames] &xsl=[XSLT stylesheet] &content-type=[mimetype for XSLT results]
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Query Syntax
• lunar
• luna*
• “apollo 11”
• lunar OR apollo
• name:apollo
• (lunar OR apollo) AND agency:united states
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Query Results
RSS 1.0 feedOpenSearch extensions (paging, relevance)
Full description of each resource
<rdf:RDF xmlns="http://purl.org/rss/1.0/" xmlns:foaf="http://xmlns.com/foaf/0.1/" xmlns:relevance="http://a9.com/-/opensearch/extensions/relevance/1.0/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:os="http://a9.com/-/spec/opensearch/1.1/" xmlns:ns.1="http://purl.org/net/schemas/space/"> <channel rdf:about=“…"> <title>lunar</title> <link>…</link> <description>Results of a search for lunar on space</description> <items> <rdf:Seq rdf:about="urn:uuid:eae4ead8-ca6a-4b12-b714-fe631d38e447"> <rdf:li resource="http://purl.org/net/schemas/space/spacecraft/LUNAR-A" /> </rdf:Seq> </items> <os:startIndex>0</os:startIndex> <os:itemsPerPage>10</os:itemsPerPage> <os:totalResults>118</os:totalResults></channel>
<item rdf:about="http://purl.org/net/schemas/space/spacecraft/LUNAR-A"> <title>Item</title> <link>http://purl.org/net/schemas/space/spacecraft/LUNAR-A</link> <relevance:score>1.0</relevance:score> <foaf:name>Lunar-A</foaf:name> <space:mass>520.0</space:mass> <space:internationalDesignator>LUNAR-A</space:internationalDesignator></item></rdf:RDF>
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Facetted Search
Similar to Amazon product search, etcGroup search results by specific fields
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/services/facet?query=[query] &fields=[comma-separated fieldnames]
&top=[10] &format=[xml|html]
<facet-results xmlns="http://schemas.talis.com/2007/facet-results#"> <head> <query>name:luna*</query>
<fields>agency</fields><top>10</top><output>xml</output>
</head> <fields> <field name="agency">
<term value="U.S.S.R" number="25" facet-uri=“…" search-uri=“…"/>
<term value="United States" number="9" facet-uri=“…" search-uri=“…"/>
<term value="Japan" number="1" facet-uri=“…" search-uri=“…"/>
<term value="India" number="1" facet-uri=“…" search-uri=“…"/>
</field> </fields></facet-results>
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Augmentation
Annotate an RSS 1.0 feed against a storeAutomatically add a description of each referenced
resource
Store Administration
Job Control, Store Configuration
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Field Predicate Map
Associate a short name to a RDF propertyProperties in field predicate map are indexed for
searchingShort name used in query syntax, sort order, etc
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<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" xmlns:bf="http://schemas.talis.com/2006/bigfoot/configuration#" xmlns:frm="http://schemas.talis.com/2006/frame/schema#“ xml:base=“http://api.talis.com/stores/space”>
<bf:FieldPredicateMap rdf:about="/indexes/default/fpmaps/default">
<frm:mappedDatatypeProperty> <rdf:Description rdf:about="/indexes/default/fpmaps/default#agency">
<frm:property rdf:resource="http://purl.org/net/schema/space/agency"/> <frm:name>agency</frm:name>
</rdf:Description> </frm:mappedDatatypeProperty>
</bf:FieldPredicateMap>
</rdf:RDF>
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Query Profile
Assign weightings to fields for searching
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<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" xmlns:bf="http://schemas.talis.com/2006/bigfoot/configuration#" xmlns:frm="http://schemas.talis.com/2006/frame/schema#“xml:base=“http://api.talis.com/stores/space”> <bf:QueryProfile rdf:about="">
<bf:fieldWeight> <rdf:Description rdf:about="/indexes/default/queryprofiles/default#name"> <bf:weight>10.0</bf:weight> <frm:name>name</frm:name> </rdf:Description> </bf:fieldWeight> <bf:fieldWeight> <rdf:Description rdf:about="/indexes/default/queryprofiles/default#agency"> <bf:weight>5.0</bf:weight> <frm:name>agency</frm:name> </rdf:Description> </bf:fieldWeight> </bf:QueryProfile></rdf:RDF>
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Job Control
Reindex, Reset, Snapshot, Restore
POST Job Request to /jobs
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<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" xmlns:bf="http://schemas.talis.com/2006/bigfoot/configuration#">
<bf:JobRequest> <rdfs:label>Reset the data in my store</rdfs:label> <bf:jobType
rdf:resource="http://schemas.talis.com/2006/bigfoot/configuration#ResetDataJob"/> <bf:startTime>2008-12-01T15:10:00Z</bf:startTime> </bf:JobRequest> </rdf:RDF>
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Jobs
Each job is a resource, with a URI
GET to monitor status, DELETE to remove
Summing Up
Summary, Additional Resources
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The Talis Platform…
• Provides a standards compliant storage infrastructure for structured and unstructured metadata
• Uses RDF to support widest possible variety of data models and integration options
• Allow managing of data assets through simple web APIs
• Offers a range of data extraction options including full-text searching, SPARQL, RSS augmentation
• Can be tailored to individual applications using the API
• Can be driven by scheduling jobs to perform data management tasks
• Is constantly evolving…
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Additional Resources
• API Reference– http://n2.talis.com/wiki/Platform_API
• Mailing List– http://groups.google.com/group/n2-dev
• Blog– http://blogs.talis.com/n2/
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Client Libraries (in various states of development)
• Moriarty– http://code.google.com/p/moriarty/
• Javascript/JQuery– http://n2.talis.com/wiki/Talis_jQuery_plugin
• Ruby Client– http://rubyforge.org/projects/talis-platform/
• Java Client– http://code.google.com/p/penry/
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