ESDSWG2011 – Semantic Web session Semantic Web Sub-group Session ESDSWG 2011 Meeting – Semantic Web sub-group session Wednesday, November 2, 2011 Norfolk, VA Brian Wilson Hook Hua

Outline 2 Intro. to Semantic Web – See tutorial materials on the Cluster page Discussion of the technology stack – What’s missing? – What should be target for the testbed and future tutorials? On-going work (sub-group & Cluster) – Organizing demos for Jan ESIP Federation meeting – Ontology development: preservation, provenance Planning for 2012 – Should SemWeb go forward as a Working Group? – What should be in the work plan? Deliverables? Segue to Casting Standards (Interoperability work) – Service, data, and event casting – Change proposals, OpenSearch extensions

Semantic Web Stack T10:15:00-05:00 Linked Open Data (LOD)

Linked Open Data T10:15:00-05:00

Resource Description Framework (RDF) Built on the triple, a 3-tuple consisting of – Subject, Predicate, and Object Example graph below: – Resource: Some entity. – Property: An attribute of a resource. – Literal: A string of characters which can be the value of a property T10:15:00-05:00. "August 16, 1999". "en".

RDF/XML Representation T10:15:00-05:00. "August 16, 1999". "en". <rdf:RDF xmlns:rdf= xmlns:dc= xmlns:exterms= August 16, 1999 en Long hand representation – URI references be written out completely, in angle brackets Short hand represetation – XML qualified name (or QName) without angle brackets – Uses form prefix:localname

Common Namespace Prefix Bindings PrefixIRI rdf: rdfs: xsd: fn: foaf: vcardhttp:// dchttp://purl.org/dc/elements/1.1/ opensearchhttp://a9.com/-/spec/opensearch/1.1/ geohttp:// T10:15:00-05:00 Not hardwired, but commonly used prefix bindings

Query Languages T10:15:00-05:00 ESIP 2011 Winter Meeting – Semantic Web Cluster SPARQL – W3C Standard query language for RDF – querying at RDF-level, not at OWL-level OWL query language (OWL-QL) – now obsolete SPARQUL – Peter Fox has been made a collaborator Query Lang – commercial and embedded QL SeRQL, RDFQuery, and many more…

What is SPARQL? Defined in terms of the W3C's RDF data model – Compatible with models that can be mapped into RDF Consists of three specifications 1.Query language specification 2.Query results XML format 3.Data access protocol SPARQL is [currently] read-only – Does not have “CRUD” operators W3C Recommendation ( ) – T10:15:00-05:00

Structure of a SPARQL Query Simple example: T10:15:00-05:00 SELECT ?project ?technology WHERE { ?project ?technology } PREFIX esip: SELECT ?project ?technology WHERE { ?project esip:worksWithTechnology ?technology } Add PREFIX namespace

SPARQL Commands SELECT – Return a table of results. – Results can be in text, XML, or even JSON ASK – Ask a boolean query. – Results can be in text, XML, or even JSON CONSTRUCT – Returns an RDF graph, based on a template in the query. DESCRIBE – Returns an RDF graph, based on what the query processor is configured to return. Show Joseki’s web SPARQL query form example.. – T10:15:00-05:00

Implementations ARQ – a SPARQL processor for Jena Pellet – OWL DL reasoner with some SPARQL query support Joseki – SPARQL server for Jena – HTTP implementation of SPARQL access protocol – Rasqal – RDF query library in Redland framework Allegrograph, and others… T10:15:00-05:00

Filtering Solutions/ regex() FILTERs restrict solutions to those for which the filter expression evaluates to TRUE. Sometimes do not know the exact resource names Use regex() for partial matches – Tests whether a literal value contains a certain substring – Case sensitive regex(?x, “Foo’) – Case insensitive regex(?x, “foo’, “I”) T10:15:00-05:00 SELECT ?s ?p ?o WHERE { ?s ?p ?o. FILTER (regex(?o, "ACCESS", "i")). } regex()’s first argument has to be either a plain literal without a language tag or a typed literal with a datatype of xsd:string. Otherwise, can using str() function to convert a resource plain literal without language tag Find all statements with “ACCESS” as the object value SELECT ?p WHERE { ?s ?p ?o. FILTER (regex(str(?p), "technology", "i")). } Find all statements that contain the substring “technology”

Modifier: ORDER BY ORDER BY sorts the results Sequence of order comparators is composed of an expression and an optional order modifier (either ASC() or DESC()). Note that it uses the “<“ operator for resource comparisons T10:15:00-05:00 SELECT ?p WHERE { ?s ?p ?o. FILTER (regex(str(?p), "technology", "i")). } Find all predicates containing the substring “technology”. SELECT ?p WHERE { ?s ?p ?o. FILTER (regex(str(?p), "technology", "i")). } ORDER BY DESC(?p) Find all predicates containing the substring “technology”. Sort results in descending order.

Query Modifiers ORDER – put the solutions in order PROJECTION – choose certain variables DISTINCT – ensure solutions in the sequence are unique REDUCE – permit elimination of some non-unique solutions OFFSET – control where the solutions start from in the overall sequence of solutions LIMIT – restrict the number of solutions T10:15:00-05:00

Pagination T10:15:00-05:00 OFFSET – Start solutions at the given offset index LIMIT – Upper bound of number of solutions Use together for pagination! SELECT DISTINCT ?s WHERE { ?s ?p ?o. } ORDER BY ASC(?s) OFFSET 0 LIMIT 5 Find all distinct subjects, but only show first page with 5 results per page. SELECT DISTINCT ?s WHERE { ?s ?p ?o. } ORDER BY ASC(?s) OFFSET 5 LIMIT 5 Find all distinct subjects, but only show second page with 5 results per page.

Outline 17 Intro. to Semantic Web – See tutorial materials on the Cluster page Discussion of the technology stack – What’s missing? – What should be target for the testbed and future tutorials? On-going work (sub-group & Cluster) – Organizing demos for Jan ESIP Federation meeting – Ontology development: preservation, provenance Planning for 2012 – Should SemWeb go forward as a Working Group? – What should be in the work plan? Deliverables? Segue to Casting Standards (Interoperability work) – Service, data, and event casting – Change proposals, OpenSearch extensions

Technology stack 18 Ontology languages – OWL-DL, OWL-Full, OWL v2 Triple Stores – Jena TDB/SDB, Virtuoso, Allegrograph – Experience with others? SPARQL Endpoints – Joseki (ARQ), Virtuoso, Sesame, Allegrograph, and many others Reasoners – Racer, Pellet, Sesame, Protégé-OWL, Allegro RDFS+ – Experience with others? Rule Languages – Jena Rules, SWRL, RIF, RuleML – Anyone using something besides Jena Rules?

What is missing? 19 What do we need more experience with? – ? What capabilities should be added to the testbed? – ?

Outline 20 Intro. to Semantic Web – See tutorial materials on the Cluster page Discussion of the technology stack – What’s missing? – What should be target for the testbed and future tutorials? On-going work (sub-group & Cluster) – Organizing demos for Jan ESIP Federation meeting – Ontology development: preservation, provenance Planning for 2012 – Should SemWeb go forward as a Working Group? – What should be in the work plan? Deliverables? Segue to Casting Standards (Interoperability work) – Service, data, and event casting – Change proposals, OpenSearch extensions

Potential Semantic Web Demos Data Quality Screening Service (DQSS) – ACCESS, C. Lynnes – Using ontology to select quality flags by dataset and apply expert-driven quality thresholds to satellite datasets, pixel by pixel Provenance Services for a MEASUREs product – Multi-Sensor Water Vapor Climatology Stratified by Cloud Classes, ACCESS, H. Hua – Capturing production provenance as logical triples in RDF format, using the Open Provenance Model (OPM) OWL ontology for interoperability – Provenance handling using SPARQL, Rules, and faceted search. Noesis 2.0 Smart Meta-Search – R. Ramachandran, part of Service & Event Casting ACCESS project (B. Wilson) – Search for relevant datasets & services across multiple back-ends: GCMD, ECHO, casts, Google, news, etc. – Uses ontology to expand query terms: broaden, narrow, synonyms Linked Open Research Data for Earth Science Informatics – Funding Friday project, E. Rozell, T. Narock – Mining AGU abstracts for links between people, papers, topics, sessions – Publish as Linked Open Data (LOD) on web in RDF/OWL format ESIP Federation People, Skills, Collaboration Database – E. Robinson – Simple ontology for people/skills/collab.; will be linked to AGU data

Other demo candidates? 22 Greg Leptoukh Eric Rozell – S2S Who else?

Outline 23 Intro. to Semantic Web – See tutorial materials on the Cluster page Discussion of the technology stack – What’s missing? – What should be target for the testbed and future tutorials? On-going work (sub-group & Cluster) – Organizing demos for Jan ESIP Federation meeting – Ontology development: preservation, provenance Planning for 2012 – Should SemWeb go forward as a Working Group? – What should be in the work plan? Deliverables? Segue to Casting Standards (Interoperability work) – Service, data, and event casting – Change proposals, OpenSearch extensions

Work Plan 24 Demonstrate these capabilities... – ? Develop ontologies for... – Preservation – Provenance – ?

Outline 25 Intro. to Semantic Web – See tutorial materials on the Cluster page Discussion of the technology stack – What’s missing? – What should be target for the testbed and future tutorials? On-going work (sub-group & Cluster) – Organizing demos for Jan ESIP Federation meeting – Ontology development: preservation, provenance Planning for 2012 – Should SemWeb go forward as a Working Group? – What should be in the work plan? Deliverables? Segue to Casting Standards (Interoperability work) – Service, data, and event casting – Change proposals, OpenSearch extensions