The Semantic Web and Web Services
Terena Conference
June 6, 2002
Charles McCathieNevile
Available online as slides, or as
a single page
Overview
Making the Web cool by making it do things
- Web Services
- Semantic Web
- Describing the things on the web
- How do they fit together?
Background
- The Web yesterday
- People reading things and interacting with them
- Web Services
- Computers interacting with things on the Web
- Semantic Web
- Computers reading things on the Web
Web services at W3C
- Web Services Activity
- XML Protocols group (since 2000)
- Web Services Architecture group (since 2002)
- Web Services Description group (since 2002)
- Leading Web Services to their full potential
- Many member submissions regarding services
- Current work based on submissions, workshop
- but think of /cgi-bin/ and forms...
New specification work
- Requirements documents (drafts)
- SOAP 1.2 (draft)
- A one-way protocol for passing objects
- Can be carried over HTTP (GET, PUT, POST, DELETE)
- supporting message/response, or pass down a chain
- WSDL - Web Services Description Language
- Describing Web Services
- Mapping to RDF
Building on existing work
- HTTP, XML
- XML schema, XML namespaces
- XML encryption, digital signature
- Internationalisation (I18N), ...
The Semantic Web
Describing the web - machine processable information
- RDF - using URIs to make statements about things
- RDF Schema, OWL - how to relate sets of statements
The web as a database, queryable like a SQL store
Part of the original design vision for the Web
RDF and XML
RDF is written in XML
XML is more used for trees, RDF for graphs
XML is good for data with pre-specified semantics
RDF is good for adding new semantics to data
Where do they fit together?
RDF can describe services and documents in the same breath
- Use cases:
- Describing services in (ever-) more detail
- Describing services for chaining together
Anyone can put their RDF descriptions on the Web
Ants and Bees (or resource discovery)
Use Case: we want food. We send out scouts, but how do they tell us where
it is?
Solution 1: Message Passing (Honey Bee Dance)
Solution 2: Shared Memory (Ant Scent Trail)
Two Modes (Table)
| Message Passing |
Shared Memory |
| Bees |
Ants |
| Mail |
Bulletin Boards |
| HTTP POST (interactive pages) |
HTTP GET, PUT (document web) |
| Doesn't change observable state of the Web |
Add to the content on the web |
Is the difference in style or substance?
Conclusions
- Web Services and RDF could both build distributed information
system
- Each mode is best in certain areas. Each could be stretched, but
- It makes more sense to capitalise on both as existing web features
we need XML for the Semantic Web, and we need RDF for Web Services