Steven Seida

How Does an RDF Knowledge Store Compare to an RDBMS?

Graph Theory Underpins RDFGraphs (Nodes & Links) are Used to

Represent a Knowledge Domain and Specifics (Instances) of It

Knowledge Domain

(Ontology)

Television Networks

Instance Data

Broadcast

News Programs

News Articles

Containing

ABC

ABC Nightly News

Broadcasts

…

Competes WithFox

Containing

…

RDF vs RDBMSCriteria Knowledge Enablement RDBM Approach

Evolving problem space - Adding knowledge representations and data is easy

Adding related columns is hard, adding related tables is very hard

Inference across problem domains and multiple sources*

- Intended for inference and general connectivity analysis

Generally no real inferencing framework. Very hard to link data across domains.

Simple query performance (simple joins and structured query)

Moderate performance after tuning - Excellent performance after tuning

Social query performance (complicated joins and recursive query to traverse a large graph)

- Moderate performance after tuning

Lots of software required and very brittle

Lots of missing data - Absent data is no issue Empty values are a headache

*For example – Finding that a suspect terrorist had a friendship in college days with the newly appointed chief of a power plant.

Practical Application -An Artist’s Impression of Knowledge in a RDBMS

Rose Kennedy’s Family

Practical Application (continued) - Knowledge in Triples (RDF) Form

<triple 32: "person2" "type" "person"><triple 33: "person2" "first-name" "Rose"><triple 34: "person2" "middle-initial" "Elizabeth"><triple 35: "person2" "last-name" "Fitzgerald"><triple 36: "person2" "suffix" "none"><triple 37: "person2" "alma-mater" "Sacred-Heart-Convent"><triple 38: "person2" "birth-year" "1890"><triple 39: "person2" "death-year" "1995"><triple 40: "person2" "sex" "female"><triple 41: "person2" "spouse" "person1"><triple 58: "person2" "has-child" "person17"><triple 56: "person2" "has-child" "person15"><triple 54: "person2" "has-child" "person13"><triple 52: "person2" "has-child" "person11"><triple 50: "person2" "has-child" "person9"><triple 48: "person2" "has-child" "person7"><triple 46: "person2" "has-child" "person6"><triple 44: "person2" "has-child" "person4"><triple 42: "person2" "has-child" "person3"><triple 60: "person2" "profession" "home-maker">

Practical Application (continued) -With a Graph Database

• You add new predicates without changing any schema

• One-to-many relations are directly encoded without the indirection of tables

• You never think about what to index because all the predicates are indexed

“There is no standard serialization of a relational database that will allow it to be imported into a competing relational database system without a change of semantics.”

Allemang and Hendler – 2008Semantic Web for the Working Ontologist

Semantic Web Vs Database Federation

Database

Query Engine

ApplicationAnalytics

User Interface

…

Database

Identical Structures and Duplication

Required!

RDF Store(merge)

Query Engine

Typical Database Federation

Semantic Web Federation

ApplicationAnalytics

User Interface

…

Webpages, Spreadsheets, Tables, Databases, etc.

Converters and Scrapers

RDF Stores and Files

-No Duplication