Databases Reference
In-Depth Information
G
RAPHS
,
RULES
,
AND
INFERENCE
The term
rules
can have multiple meanings that depend on where you're coming from
and the context of the situation. Here, we use the term to define abstract rules that
relate to an understanding of objects in a system, and how the object properties allow
you to gain insight into and better use large datasets.
RDF
was designed to be a standard way to represent many types of problems in the
structure of a graph. A primary use for
RDF
is to store logic and rules. Once you've set
these rules up, you can use an inference or rules engine to discover other facts about a
system.
In our section on link analysis, we looked at how text can be encoded with entities
such as people and dates to help you find facts. We can now take things a step further
to get additional information from the facts that will help you solve business problems.
Let's start with trust, since it's an important aspect for businesses who want to
attract and retain customers. Suppose you have a website that allows anyone to post
restaurant reviews. Would there be value in allowing you to indicate which reviewers
you trust? You're going out to dinner and you're considering two restaurants. Each
restaurant has positive and negative reviews. Can you use simple inference to help you
decide which restaurant to visit?
As a first test, you could see if your friends reviewed the restaurants. But a more
powerful test would be to see if any of your friends-of-friends also reviewed the restau-
rants. If you trust John and John
trusts Sue, what can you infer about
your ability to trust Sue's restaurant
recommendations? Chances are that
your social network will help you use
inference to calculate what reviews
should have more weight. This is a
simple example of using networks,
graphs, and inference to gain addi-
tional knowledge on a topic. The use
of
RDF
and inference isn't limited to
social networks and product reviews.
RDF
is a general-purpose structure
that can be used to store many forms
of business logic.
The
W3C
does more than define
RDF
; it has an entire framework of
standards for using
RDF
to solve busi-
ness problems. This framework is fre-
quently referred to as the
Semantic
Web
User interface and applications
Trust
Proof
Unifying logic
Ontologies:
OWL
Rules:
RIF/SWRL
Querying:
SPARQL
Taxonomies: RDFS
Data interchange: RDF
Syntax: XML
Identifiers: URI
Character set: UNICODE
Figure 4.16
A typical semantic web stack with
common low-level standards like URI, XML, and RDF
at the bottom of the stack. The middle layer includes
standards for querying (SPARQL) and standards for
rules (RIF/SWRL). At the top of the stack are user
interface and application layers above abstract layers
of logic, proof, and trust building.
Stack
.
Some
of
these
are
described in figure 4.16.
