Open Conceptual Data Models <ul><ul><li>Making the Conceptual Layer Real </li></ul></ul><ul><ul><li>via </li></ul></ul><ul...
Situation Analysis <ul><li>Linked Data Vision: </li></ul><ul><li>The transition of the HTTP based Webs (Intranet, Extranet...
Open Conceptual Data Models <ul><li>Topics: </li></ul><ul><li>Conceptual & Logical Data Models </li></ul><ul><li>Conceptua...
Data Model Layers <ul><li>Physical </li></ul><ul><ul><li>How data is physically represented on disk </li></ul></ul><ul><li...
Logical Data Model <ul><li>Most prominent of the three data model types  </li></ul><ul><li>Main focus of database driven a...
Logical Data Model Weaknesses <ul><li>Impedance Mismatch </li></ul><ul><li>SQL expresses queries in terms of tables / view...
Logical Data Model Weaknesses <ul><li>Loss of Semantic Fidelity During Development </li></ul><ul><li>Process: </li></ul><u...
Logical Data Model Weaknesses <ul><li>Heterogeneous Databases & Interoperability </li></ul><ul><li>Logical data model </li...
Conceptual Models for Linked Data Webs <ul><li>Explosion of User Generated Data from Web 2.0 applications and their Data S...
Benefits of Conceptual Models <ul><li>More faithfully represents human view of domain of interest </li></ul><ul><li>Concep...
Application Areas – Present & Future <ul><li>Social Media, eCommerce, Distributed Collaborative Apps. </li></ul><ul><ul><l...
Semantic Web Project Technologies <ul><li>These technologies offer: </li></ul><ul><li>Ontologies </li></ul><ul><li>For rep...
Realizing Conceptual Models <ul><li>Ontologies </li></ul><ul><li>Provide the building blocks for conceptual models </li></...
Goodness of Fit <ul><li>RDF was designed from the ground up as a metadata data model </li></ul><ul><li>RDF / RDFS / OWL wo...
Semantic Expressivity Comparison <ul><li>Data Definition Language (DDL)-based Relational Model </li></ul><ul><li>Relations...
RDF Conceptual Model – Artist / Records / Tracks © 2008 OpenLink Software, All rights reserved
Global Granular Information Sharing <ul><li>Traditional Logical/Relational Data Model </li></ul><ul><li>Schema described b...
Linked Data – What is It? <ul><li>A method for exposing, sharing & connecting data on HTTP based Data Networks. </li></ul>...
Linked Data – Why Is It Important <ul><li>It exposes the compound nature of Data Containers (e.g., Documents) such that </...
Linked Data Model © 2008 OpenLink Software, All rights reserved Changes the focus from linked documents to linked entities...
Hyperdata Links Between Data Items © 2008 OpenLink Software, All rights reserved
Linked Data Benefits – Data Exploration <ul><li>Natural Navigation Through Typed Links </li></ul><ul><li>RDF entities (ins...
Linked Data Benefits - Aggregatable Data <ul><li>Often desirable to have an  integrated view  of all the data available ab...
Linked Data – Data Aggregation © 2008 OpenLink Software, All rights reserved
Linked Data Benefits - Self Describing Data <ul><li>Resource Description Framework (RDF) </li></ul><ul><li>A technology fo...
Linked Data Benefits - SPARQL <ul><li>If a user agent has no built-in knowledge of a particular Data Item, it can derefere...
Virtuoso - Linked Data Generation Options <ul><li>Conceptual layer insulates Linked Data consumers from RDFization infrast...
Virtuoso RDF based Linked Data Views <ul><li>Expose relational model data as RDF graph model data </li></ul><ul><li>Provid...
© 2008 OpenLink Software, All rights reserved Northwind Demo Database: RDF View Definition Extract prefix northwind: <http...
Northwind Demo Database: Customer Table to RDF  data item  Mapping © 2008 OpenLink Software, All rights reserved Orders Ta...
LinqToRdf + Virtuoso © 2008 OpenLink Software, All rights reserved
LinqToRdf to MusicBrainz - Conceptual Model Veneer © 2008 OpenLink Software, All rights reserved
ADO.NET Data Services & Entity Data Model <ul><li>A framework for exposing ‘pure data’ service over HTTP </li></ul><ul><li...
ADO.NET Data Services & Entity Data Model <ul><li>Server-side only conceptual model </li></ul><ul><li>Powerful URL address...
ADO.NET Data Services & Entity Data Model <ul><li>No Support for Non-SQL Data Sources </li></ul><ul><li>Astoria is aimed e...
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Making the Conceptual Layer Real via HTTP based Linked Data

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A presentation that addresses pros and cons associated with approaches to making concrete conceptual models real. It covers HTTP based Linked Data and RDF data model as new mechanism for conceptual model oriented data access and integration.

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Making the Conceptual Layer Real via HTTP based Linked Data

  1. 1. Open Conceptual Data Models <ul><ul><li>Making the Conceptual Layer Real </li></ul></ul><ul><ul><li>via </li></ul></ul><ul><ul><li>HTTP based </li></ul></ul><ul><ul><li>Linked Data (aka. Linked Data) </li></ul></ul>© 2008 OpenLink Software, All rights reserved
  2. 2. Situation Analysis <ul><li>Linked Data Vision: </li></ul><ul><li>The transition of the HTTP based Webs (Intranet, Extranet, or Internet) </li></ul><ul><ul><li>from a Webs of Linked Documents </li></ul></ul><ul><ul><li>to Webs of interlinked Structured Data Items (aka: entities, data objects, resources) </li></ul></ul><ul><li>Concurrent trend in the IT industry: </li></ul><ul><li>A recognition of the benefits of conceptual data models over logical data models </li></ul><ul><li>The Big Question: </li></ul><ul><li>To what extent does Linked Data support conceptual level data models ? </li></ul>© 2008 OpenLink Software, All rights reserved
  3. 3. Open Conceptual Data Models <ul><li>Topics: </li></ul><ul><li>Conceptual & Logical Data Models </li></ul><ul><li>Conceptual Models for the Semantic Web </li></ul><ul><li>Realizing Conceptual Models through Ontologies & Linked Data </li></ul><ul><li>Virtuoso’s RDF based Linked Data Views </li></ul><ul><li>ADO.NET Data Services & the Entity Data Model </li></ul>© 2008 OpenLink Software, All rights reserved
  4. 4. Data Model Layers <ul><li>Physical </li></ul><ul><ul><li>How data is physically represented on disk </li></ul></ul><ul><li>Logical (aka logical schema) </li></ul><ul><ul><li>Expresses problem domain in terms of data management technology (tables / columns) </li></ul></ul><ul><ul><li>e.g. relational schema </li></ul></ul><ul><li>Conceptual (aka conceptual schema) </li></ul><ul><ul><li>Purely semantic description of problem space </li></ul></ul><ul><ul><li>Describes things (entities), their characteristics (attributes) & associations between things (relationships) </li></ul></ul>© 2008 OpenLink Software, All rights reserved
  5. 5. Logical Data Model <ul><li>Most prominent of the three data model types </li></ul><ul><li>Main focus of database driven applications </li></ul><ul><ul><li>Due to pervasiveness of relational database driven applications within the enterprise and across the Web </li></ul></ul><ul><li>Weaknesses </li></ul><ul><li>Impedance mismatch </li></ul><ul><li>Loss of semantics during development process </li></ul><ul><li>Heterogeneous databases & interoperability </li></ul>© 2008 OpenLink Software, All rights reserved
  6. 6. Logical Data Model Weaknesses <ul><li>Impedance Mismatch </li></ul><ul><li>SQL expresses queries in terms of tables / views </li></ul><ul><ul><li>=> targets logical schema </li></ul></ul><ul><li>Normalization fragments the data model </li></ul><ul><ul><li>Entities & their attributes may be split across several tables </li></ul></ul><ul><ul><li>Navigation between objects requires relational joins over two or more tables </li></ul></ul><ul><ul><li>Table rows must be reconstituted into higher level conceptual entities </li></ul></ul><ul><li>Conceptual level data model is desirable to: </li></ul><ul><li>Remove impedance mismatch </li></ul><ul><li>Isolate application from changes to logical data model </li></ul><ul><li>Provide framework for productive human level interaction </li></ul>© 2008 OpenLink Software, All rights reserved
  7. 7. Logical Data Model Weaknesses <ul><li>Loss of Semantic Fidelity During Development </li></ul><ul><li>Process: </li></ul><ul><li>Develop conceptual model (E-R modelling) </li></ul><ul><li>Transform to logical model for implementation </li></ul><ul><li>DBMS generates physical model </li></ul><ul><li>Problems: </li></ul><ul><li>Each move to a lower level model depreciates semantic fidelity of the higher level model </li></ul><ul><li>Conceptual Model semantics fragmented across schema / business rules / application code </li></ul><ul><li>Application & Users must understand logical data model </li></ul><ul><ul><li>Must be hardcoded or inferred (imperfectly) from system tables </li></ul></ul>© 2008 OpenLink Software, All rights reserved
  8. 8. Logical Data Model Weaknesses <ul><li>Heterogeneous Databases & Interoperability </li></ul><ul><li>Logical data model </li></ul><ul><li>Describes problem domain in terms of tables/columns </li></ul><ul><li>Requires costly table joins to navigate model </li></ul><ul><li>Application </li></ul><ul><li>Exposed to specifics of a particular vendor’s RDBMS </li></ul><ul><li>In heterogeneous database environment , must handle </li></ul><ul><li>Different SQL dialects </li></ul><ul><li>Different schemas </li></ul><ul><ul><li>No explicit data model. No explicit semantics. </li></ul></ul><ul><li>Interoperability/integration = perpetual problem for IT depts </li></ul>© 2008 OpenLink Software, All rights reserved
  9. 9. Conceptual Models for Linked Data Webs <ul><li>Explosion of User Generated Data from Web 2.0 applications and their Data Silos is driving the recognition of the need to move from logical to conceptual models, exemplified by: </li></ul><ul><li>Microsoft’s Entity Data Model / Entity Framework </li></ul><ul><li>W3C’s Semantic Web Project which includes powerful technologies for this paradigm shift such as: </li></ul><ul><ul><li>Resource Description Framework (RDF Data Model and Data Representation Formats) </li></ul></ul><ul><ul><li>Web Ontology Language (OWL) </li></ul></ul><ul><ul><li>SPARQL (Query Language, RESTful Interface, and Query Result Serialization Formats) </li></ul></ul>© 2008 OpenLink Software, All rights reserved
  10. 10. Benefits of Conceptual Models <ul><li>More faithfully represents human view of domain of interest </li></ul><ul><li>Conceptual model & semantics </li></ul><ul><ul><li>Explicit & available globally </li></ul></ul><ul><ul><li>Not implicit & fragmented across business logic / UI etc </li></ul></ul><ul><li>Better / explicit semantics facilitates move from “search” to “esoteric precision find” </li></ul><ul><li>Much easier heterogeneous data integration </li></ul><ul><ul><li>User Generated Data is inherently heterogeneous & disparately located </li></ul></ul>© 2008 OpenLink Software, All rights reserved
  11. 11. Application Areas – Present & Future <ul><li>Social Media, eCommerce, Distributed Collaborative Apps. </li></ul><ul><ul><li>Require shareable, standards-based, cross-platform conceptual views of data </li></ul></ul><ul><li>Data portability </li></ul><ul><ul><li>Needed as users maintain multiple points of presence & identity across – blogs, social network accounts etc. </li></ul></ul><ul><li>Open business models </li></ul><ul><ul><li>Require exchange & integration of large amounts of data </li></ul></ul><ul><li>Scientific research – sharing of knowledge & findings </li></ul><ul><ul><li>Requires transparent access to distributed heterogeneous data </li></ul></ul><ul><ul><li>Requires database integration using global schema </li></ul></ul><ul><li>Autonomous intelligent agents </li></ul><ul><ul><li>Free humans from large-volume data processing </li></ul></ul>© 2008 OpenLink Software, All rights reserved
  12. 12. Semantic Web Project Technologies <ul><li>These technologies offer: </li></ul><ul><li>Ontologies </li></ul><ul><li>For representing common semantics </li></ul><ul><ul><li>Spanning databases, applications, enterprises, on-line communities </li></ul></ul><ul><li>Deliver shared conceptual model </li></ul><ul><li>Provide common schemas (Dublin Core, FOAF, SIOC, GoodRelations etc) </li></ul><ul><li>Common Semantics (Ontologies) & Common Data Representation (RDF) </li></ul><ul><li>Enable cross data source querying using SPARQL </li></ul><ul><ul><li>Data across several databases (or data spaces) can be meshed, expanded, and explored </li></ul></ul><ul><ul><li>Querying using proprietary APIs unnecessary </li></ul></ul><ul><ul><li>Brute force data merging via code is unnecessary </li></ul></ul><ul><li>Open Data Formats, Platform Independence, Common Models </li></ul><ul><li>Facilitate data portability, accessibility, and integration. </li></ul>© 2008 OpenLink Software, All rights reserved
  13. 13. Realizing Conceptual Models <ul><li>Ontologies </li></ul><ul><li>Provide the building blocks for conceptual models </li></ul><ul><li>Define the concepts and their relationships in a domain of interest (or world view) </li></ul><ul><li>Describing Classes & Properties – Ontology Languages </li></ul><ul><li>RDFS </li></ul><ul><ul><li>Introduces the notions of concepts (classes) & instances </li></ul></ul><ul><li>OWL </li></ul><ul><ul><li>Adds more vocabulary for describing: </li></ul></ul><ul><ul><ul><li>relations between classes </li></ul></ul></ul><ul><ul><ul><li>cardinality </li></ul></ul></ul><ul><ul><ul><li>richer typing of properties, etc. </li></ul></ul></ul>© 2008 OpenLink Software, All rights reserved
  14. 14. Goodness of Fit <ul><li>RDF was designed from the ground up as a metadata data model </li></ul><ul><li>RDF / RDFS / OWL work directly at the level of conceptual models </li></ul><ul><li>Conceptual model terminology matches RDF/OWL terminology </li></ul><ul><ul><li>Concepts, entities, attributes, relationships. </li></ul></ul><ul><li>A natural fit! </li></ul><ul><li>RDF lends itself naturally to describing conceptual models. </li></ul>© 2008 OpenLink Software, All rights reserved
  15. 15. Semantic Expressivity Comparison <ul><li>Data Definition Language (DDL)-based Relational Model </li></ul><ul><li>Relationship between two entities isn’t explicit </li></ul><ul><li>Foreign key relating two rows in separate tables doesn’t express the nature of the relationship </li></ul><ul><li>Semantics must often be inferred from table definitions </li></ul><ul><li>RDF-based Conceptual Model </li></ul><ul><li>Relationship between two entities is stated explicitly by predicate in subject-predicate-object triple </li></ul><ul><li>Semantic expressivity of RDF/RDFS/OWL is much better than DDL </li></ul><ul><li>Has richer semantic content than equivalent DDL-based logical/relational model </li></ul>© 2008 OpenLink Software, All rights reserved
  16. 16. RDF Conceptual Model – Artist / Records / Tracks © 2008 OpenLink Software, All rights reserved
  17. 17. Global Granular Information Sharing <ul><li>Traditional Logical/Relational Data Model </li></ul><ul><li>Schema described by DDL is internal to DBMS </li></ul><ul><li>Primary keys identifying an individual table row (i.e. entity instance) not globally unique, not easily usable outside host DBMS </li></ul><ul><li>Gives rise to ‘data silos’ </li></ul><ul><li>RDF’s use of Generic HTTP-based URIs </li></ul><ul><li>Externalises the data and schema </li></ul><ul><li>Makes both globally accessible & scalable </li></ul><ul><li>Provides globally unique IDs for entities/relations/classes </li></ul><ul><li>A vehicle for granular, global information sharing down to the equivalent of the record level. </li></ul>© 2008 OpenLink Software, All rights reserved
  18. 18. Linked Data – What is It? <ul><li>A method for exposing, sharing & connecting data on HTTP based Data Networks. </li></ul><ul><li>A term coined by Tim Berners-Lee that describes a RESTful mechanism for HTTP based Data Access & Manipulation by Reference </li></ul><ul><li>A record level HTTP based Open Data Access & Connectivity mechanism </li></ul><ul><li>A richer hyperlinking mechanism that takes us from Hypertext Links (Document to Document) to Hyperdata Links (Data Item to Data Item). </li></ul>© 2008 OpenLink Software, All rights reserved
  19. 19. Linked Data – Why Is It Important <ul><li>It exposes the compound nature of Data Containers (e.g., Documents) such that </li></ul><ul><ul><li>Data Containers are uniquely identified & referenceable </li></ul></ul><ul><ul><li>Data Items within Data Containers are uniquely identified & referencable </li></ul></ul><ul><li>It provides a conceptual model oriented Open Data Access & Connectivity mechanism </li></ul><ul><li>It delivers a powerful mechanism for meshing disparate and heterogeneous data sources. </li></ul>© 2008 OpenLink Software, All rights reserved
  20. 20. Linked Data Model © 2008 OpenLink Software, All rights reserved Changes the focus from linked documents to linked entities The document as a data container becomes less relevant
  21. 21. Hyperdata Links Between Data Items © 2008 OpenLink Software, All rights reserved
  22. 22. Linked Data Benefits – Data Exploration <ul><li>Natural Navigation Through Typed Links </li></ul><ul><li>RDF entities (instance data, classes, and properties) are identified by dereferencable HTTP URIs </li></ul><ul><li>Navigating from one data item to another is easy via: </li></ul><ul><ul><li>Single LINK click from any HTTP user agent commences data item relationship navigation </li></ul></ul><ul><ul><li>Linked Data Browers such as OpenLink Data Explorer </li></ul></ul><ul><li>Relational/Logical Model </li></ul><ul><li>Cumbersome </li></ul><ul><li>Requires SQL joins + typically Object-Relational mapping </li></ul><ul><li>e.g. in C# : track = lennonAlbum.Tracks[“Imagine”] </li></ul>© 2008 OpenLink Software, All rights reserved
  23. 23. Linked Data Benefits - Aggregatable Data <ul><li>Often desirable to have an integrated view of all the data available about an item or topic </li></ul><ul><li>Database Realm </li></ul><ul><li>Integration problematic, difficult to combine logical schemas </li></ul><ul><li>Semantic Web </li></ul><ul><li>Data aggregation is easy: every resource has a unique URI </li></ul><ul><ul><li>Individual items can be linked </li></ul></ul><ul><ul><li>Conceptual models can be linked </li></ul></ul><ul><li>Cross-domain links enrich domain knowledge </li></ul><ul><li>Different facets of the same data item may be described by different URIs minted by different authors </li></ul><ul><ul><li>Can be linked. e.g. owl:sameAs, rdf:type predicates </li></ul></ul><ul><ul><li>May expose facts not directly represented in any one source </li></ul></ul>© 2008 OpenLink Software, All rights reserved
  24. 24. Linked Data – Data Aggregation © 2008 OpenLink Software, All rights reserved
  25. 25. Linked Data Benefits - Self Describing Data <ul><li>Resource Description Framework (RDF) </li></ul><ul><li>A technology for creating self-describing Web resources </li></ul><ul><li>Data Item’s type definition ‘accompanies’ it via rdfs:type relations </li></ul><ul><li>An RDF based data can be queried using SPARQL without knowing anything beforehand about the data definition (schema comes last in this realm) </li></ul><ul><li>Provides the basis for powerful deductive data exploration tools </li></ul><ul><li>Logical / Relational Schema </li></ul><ul><li>Users / applications need a detailed understanding of the schema to use and navigate the data </li></ul><ul><li>Application’s knowledge of the schema typically hardcoded </li></ul><ul><li>Ad-hoc end-user data exploration potentially error prone </li></ul>© 2008 OpenLink Software, All rights reserved
  26. 26. Linked Data Benefits - SPARQL <ul><li>If a user agent has no built-in knowledge of a particular Data Item, it can dereference its Generic HTTP URI to obtain such information </li></ul><ul><li>The Power of SPARQL </li></ul><ul><li>Discover what sorts of things a data source contains </li></ul><ul><li>select distinct ?URI ?ObjectType where { ?URI a ?ObjectType } </li></ul><ul><li>Determine all the properties of an data item’s class </li></ul><ul><li>select * where { <http://my.org/resourceTypes/Department> ?property ?hasValue } </li></ul><ul><li>Determine all the properties and values of an data item instance </li></ul><ul><li>DESCRIBE <http://my.org/resource/Accounts> </li></ul><ul><li>No prior knowledge of the RDF data source is needed </li></ul>© 2008 OpenLink Software, All rights reserved
  27. 27. Virtuoso - Linked Data Generation Options <ul><li>Conceptual layer insulates Linked Data consumers from RDFization infrastructure & data source heterogeneity </li></ul>© 2008 OpenLink Software, All rights reserved
  28. 28. Virtuoso RDF based Linked Data Views <ul><li>Expose relational model data as RDF graph model data </li></ul><ul><li>Provide the means to move from a logical model to a conceptual model view </li></ul><ul><li>Available for querying through SPARQL or SPASQL (SPARQL embedded in SQL) </li></ul><ul><li>No physical regeneration of relational data </li></ul><ul><li>RDF Views = </li></ul><ul><ul><li>Virtuoso RDF Meta-Schema (MSL) + </li></ul></ul><ul><ul><li>Meta-Schema Language </li></ul></ul><ul><li>MSL = </li></ul><ul><ul><li>A domain specific, declarative language for mapping a logical SQL data model to a conceptual RDF data model </li></ul></ul>© 2008 OpenLink Software, All rights reserved
  29. 29. © 2008 OpenLink Software, All rights reserved Northwind Demo Database: RDF View Definition Extract prefix northwind: <http://www.openlinksw.com/schemas/northwind#> … create iri class northwind:Customer <http://^{URIQADefaultHost}^/Northwind/Customer/%U#this> (in customer_id varchar not null) … alter quad storage virtrdf:DefaultQuadStorage … from Demo.demo.Customers as customers from Demo.demo.Orders as orders … { Demo.demo.Customers Northwind RDF View Definition create virtrdf:NorthwindDemo as graph iri (“http://^{URIQADefaultHost}^/Northwind”) { … northwind:Customer(customers.CustomerID) a foaf:Organization as virtrdf:Customer-CustomerID ; northwind:companyName customers.CompanyName as … ; … northwind:fax customers.Fax as virtrdf:Customer-fax . … } } northwind:Customer(orders.CustomerID) northwind:has_order northwind:Order(orders.OrderID) as virtrdf:Order-has_order . Customer ID Company Name Contact Name Contact Title Address City Postal Code Country Phone Fax
  30. 30. Northwind Demo Database: Customer Table to RDF data item Mapping © 2008 OpenLink Software, All rights reserved Orders Table Customer ID Company Name Contact Name Contact Title Address City Postal Code Country Phone Fax ALFKI Alfreds Futterkiste Maria Anders Sales Represe-ntative Obere Str. 57 Berlin 12209 Germany 030 - 0074321 030 - 0076545 companyName contactName contactTitle address city PostalCode country phone fax Alfreds Futterkiste Maria Anders Sales Representative Obere Str. 57 Berlin 12209 Germany 030-0074321 030-0076545 … Order/10643#this has_order Order/10692#this … has_order Customer/ALFKI#this prefix <http://demo.openlinksw.com/Northwind/> has_customer has_customer Order ID Customer ID … 10643 ALFKI … 10692 ALFKI …
  31. 31. LinqToRdf + Virtuoso © 2008 OpenLink Software, All rights reserved
  32. 32. LinqToRdf to MusicBrainz - Conceptual Model Veneer © 2008 OpenLink Software, All rights reserved
  33. 33. ADO.NET Data Services & Entity Data Model <ul><li>A framework for exposing ‘pure data’ service over HTTP </li></ul><ul><li>No support for RDF </li></ul><ul><li>Fails to imbibe any of RDF’s inherent benefits </li></ul><ul><li>Lack of platform independence & standards compliance </li></ul><ul><li>Supports REST-style interfaces </li></ul><ul><li>Supports Atom, JSON and XML payloads </li></ul><ul><li>But </li></ul><ul><li>Server-side: Windows only </li></ul><ul><li>Consuming Astoria services at a higher level requires Windows .NET client or Silverlight-supported browser </li></ul>© 2008 OpenLink Software, All rights reserved
  34. 34. ADO.NET Data Services & Entity Data Model <ul><li>Server-side only conceptual model </li></ul><ul><li>Powerful URL addressing to query/navigate/sort/filter etc </li></ul><ul><ul><li>Customers collection: http://myserver/data.svc/Customers </li></ul></ul><ul><ul><li>Customer ALFKI: http://myserver/data.svc/Customers('ALFKI') </li></ul></ul><ul><ul><li>Customer ALFKI's orders: http://myserver/data.svc/Customers('ALFKI')/Orders </li></ul></ul><ul><li>But </li></ul><ul><li>Client must know conceptual schema </li></ul><ul><ul><li>e.g. to construct above URIs </li></ul></ul><ul><li>Lack of Deferencable Entity IDs </li></ul><ul><li>Ability to discover entities and dereference their descriptions (attributes/relations) is confined to the facilities offered by .NET </li></ul><ul><li>c.f. SPARQL’s ability to handle unknown data sources </li></ul>© 2008 OpenLink Software, All rights reserved
  35. 35. ADO.NET Data Services & Entity Data Model <ul><li>No Support for Non-SQL Data Sources </li></ul><ul><li>Astoria is aimed exclusively at making relational data Web accessible </li></ul><ul><li>c.f. Linked Data Realm </li></ul><ul><li>Recognize that vast amounts of data resides in unstructured and semi-structured data sources </li></ul><ul><li>Support for embedding RDF into existing (X)HTML </li></ul><ul><ul><li>RDFa, GRDDL, eRDF </li></ul></ul><ul><li>Emerging tools for converting non-RDF data to RDF model data </li></ul><ul><li>Emerging tools for exposing Relational data as RDF Graph Model data </li></ul><ul><li>Astoria lacks scalability & scope of Semantic Web technologies </li></ul>© 2008 OpenLink Software, All rights reserved
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