Transcript Next Generation - Molde University College

The Next Generation Web
You see things; and you say “Why?”
But I dream things that never were; and I say “Why not?”
G. B. Shaw (Back to Methuselah)
Michael B. Spring
Department of Information Science and Telecommunications
University of Pittsburgh
[email protected]
http://www.sis.pitt.edu/~spring
Prelude
When I try to explain the architecture now
[for the semantic web], I get the same
distant look in people’s eyes as I did in
1989, when I tried to explain how global
hypertext [the world wide web] would
work.
• Tim Berners-Lee, Weaving the Web, pp.194-195
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Overview
•
•
•
•
Context
Changing nature of documents
The current state of the WWW
The next generation web
– Conceptually
– Infrastructure
– Proposed Architectures
Simple
Concepts
Ideas
for a
Technical
Solution
• Issues and conclusions
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Context
• The Web is a critical environment for information
exchange and is increasingly used by business
• Documents are changing in form and function;
computer mediation is making them more
dynamic, more interactive, and more personal
• Powerful existing computing tools and
infrastructure to support collaboration, distributed
services, and agents are being retooled for a
second generation web
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Artifacts and process
• Humans use documents as tools to accomplish
different things:
– Explanation of ideas
– Communication of design
– Specification of agreements
• In addition to their main message, documents
provide ancillary information about work
processes (feedback and feedthrough)
• The next generation web will embrace computer
mediated and manipulable document forms
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Types of documents
• Classifying documents by scope captures many of
the important distinctions between different types.
• Consider the difference in documents that are:
–
–
–
–
–
Personal
Group
Organizational
Enterprise
Archival
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Document Process matrix
Tools for Creating
Enterprise Documents
Archival
Enterprise
Corporate
Group
Personal
Create
Disseminate
Store/Retrieve
Use
Work
Processes
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Tools
Standards
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Standards for the
storage of Group
Documents
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Digital Document
Characteristics
• Digital documents have new features:
– Components (charts, data sheets)
– Active links
– Versioning and commentary
• We work with digital documents differently
– Increased number of revisions, more copy and edit
– Outline and fill composition
• Computers can work with digital documents
– Automatic generation
– Agent based processing
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The Current State of the Web
– Disintermediated junk
– Unlinkable processes
– Insufficient inverted indices
• Classification is needed
2000
Classification
• The web has begun to lose
coherence -- locational
association is not enough
– It requires a shared ontology
– It needs to be distributed
– It must be decentralized
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1990
300BC
Linking
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What the WWW is
• The web is distributed, decentralized and
scalable system with
– A robust simple idempotent protocol (single
request & response)
– Based on a locational infrastructure (URLs and
DNS)
– With an effective but costly envelop (TCP)
– And a growing ad hoc superstructure (server
and client sides)
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What the WWW is not
• Stateful
– Cookies and server side session management struggle
to provide a semblance of state
• Organized
– Search engines and portals are veneers that endeavor to
provide organization
• Designed for processes
– http is connectionless and cannot support sessions
– HTML is inadequate for data interchange
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The Next Generation Is Here
• When a CGI program takes data from a DBMS to
compose a web page with a form that is processed
by another CGI, that is in essence a web service
• When a plug-in such as real-player accesses and
plays streaming media, we are in essence using a
web service
• Instant messaging and file sharing services such as
Gnutella are better examples of services. More
fully integrated in browsers, they are web services
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A Once and Future King
• The next generation is not really new -- distributed
computing, based on a client server model, has
been with us for years.
• RPC and RMI approaches to distributed
computing are multi-tiered, involve registration
and lookup, and make use of shared interfaces.
• CORBA and DCOM provide process wrappers
and distributed lookups.
• The next generation web is distributed computing
– dynamic, late binding, peer to peer architectures.
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The Next Generation Web
Conceptually
• Use the vast infrastructure of the web
(millions of clients and servers using http)
to access programs as well as static pages.
• Develop additional infrastructure that will
allow highly distributed programs to operate
securely and productively over the web.
• Build “marketplaces” that work.
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Infrastructure and Architecture
• The underlying infrastructure includes
–
–
–
–
Component transaction monitors
Abstract syntax
Distributed directory services
Security and authentication
• The architectural approaches are varied:
–
–
–
–
HP’s E-service architectures (now absorbed)
Sun’s JXTA (still emerging)
Microsoft’s .NET (growing strong)
W3C’s semantic web with its agent architectures (???)
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CTM Infrastructure
• Component Transaction Monitors (CTMs) are
CGIs on steroids
• Early efforts moved beyond CGI to servlet runners
and ASP/JSP with components/beans.
• CTM moves beyond managing threads to
advertising, federation, transaction management,
and security management.
• To deliver messages to components through http,
an envelop is needed. The Simple Object Access
Protocol (SOAP) is emerging as the protocol.
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XML Infrastructure
• Data Interchange
– In order to build documents that can be
machine processed, we need more precise
control over the structure of the document (we
need to know there is an author element).
– We also need control over the content of the
document (we need to control what goes in the
author element).
• XML provides both of these capabilities
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XML Infrastructure(continued)
• Given a clear model of XML documents:
– XPath defines the ability to obtain any set of
nodes in a document
– XSLT allows the transformation of document
trees
– DOM and SAX provide application program
interfaces to these models
– Schema allow extensible and modular
extension of definitions
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Directory Infrastructure
• Directories of objects are key to the infrastructure.
They will be distributed and object oriented.
• The X.500 Directory Service is being used via
LDAP(Lightweight Directory Access Protocols)
• The directories will be used to allow resources to
advertise themselves so as to be discovered. The
Universal Description, Discovery and Integration
(UDDI) Protocol is emerging as a leader here
• There are a number of models for how directories
will be related.
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Security and Authentication
• CTMs will implement secure pipes of various
types between monitors to allow transactions that
begin and end behind firewalls to move across the
unprotected internet.
• Certificates will be used as the basis for the
development of a web of trust that will allow for
authentication and non-repudiation
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Approaches to Marketplaces
• Michael Dertouzous suggested that this
environment we are moving toward most closely
resembles and information marketplace
– HP’s e-speak was an early contender
– SUN’s JXTA has many similar characteristics, a tight
coupling to Java, and a simple Unix like approach
– Microsoft’s .NET is focused on bringing Microsoft’s
extensive resources to bear in easy to use ways
– The Semantic Web is a personal agent based view of
how this new web might be used
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What is E’speak (1)
• E’speak is a component transaction monitor
E’Speak Services
E’speak Engine
Consumer
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What is E’Speak (2)
• E’Speak is a distributed service
E’Speak Services
LDAP
E’speak Engine
E’speak Engine
E’Speak Services
Consumer
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E’Speak Services
E’speak Engine
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E’Speak Services
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What is E’Speak (3)
• E’Speak is a system that provides support
for:
–
–
–
–
Advertising and finding based on vocabularies
Authentication
Multiple access methods
Security
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E”Speak
Advertising and Authentication
E’Speak Services
LDAP
E’speak Engine
E’Speak Services
E’speak Engine
Consumer
Certificates
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E”Speak Access and Security
LDAP
E’Speak Services
E’speak Engine
E’Speak Services
Secure
E’speak Engine
Consumer
E’Speak Services
Web Server
with Servlets
E’speak Engine
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What is E’Speak (4)
• E’speak is an extensible system with
decentralized control:
– Vocabularies
• Attributes and values
• Combined and advertised
– Services
• Basic services
• Infrastructure services
• Support services
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Vocabularies and Metaservices
Client
E’Speak
Core
E’Speak Services
E’speak Engine
Infrastructure
Services
Repository
Basic Services
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Support
Services
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A Mind Set
•
•
•
•
•
•
•
•
Millions of machines
Marketplace makers
Competing service providers
Dynamic offerings
Distributed certificate authorities
Intermediaries
Smart devices
“Smart” consumers
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E-Marketplaces
CA
LDAP
E’speak
Engine
E’speak
Engine
E’speak
Engine
CA
E’speak
Engine
E’speak
Engine
CA
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JXTA
• Peer to peer P2P computing model
• JXTA comes from juxtapose – the peer to
peer model is juxtaposed against the
traditional client server model.
• It consists of a federation of peers running
JXTA cores
• The focus of this implementation is on truly
ad hoc peers
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JXTA Architecture
JXTA Application
Peers
Pipes
JXTA Service
Services
Discovery
Peer Groups
Pipe Binding
Rendezvous
Access
Propagation
Relay
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Network Services
Routing
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JXTA Components
• Peers are the fundamental entities in JXTA
– They offer and/or consume services
– They have a unique ID but may be mobile
• Pipes are used to connect peers
– They are late binding and dynamic
– They are considered one way and unreliable
• Services consist of both peer services and peergroup services which may be offered redundantly
by all members of a peer group
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JXTA Services
• Discovery along with propagation and rendezvous
are all related to the processes by which entities
and services become known
• Advertisements are made by participants that are
propagated, cached by rendezvous services, such
that they might be discovered.
• Once discovered, services may be engaged
through a series of messages
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JXTA Services (continued)
• The rendezvous service keeps track of known
advertisements and other rendezvous services –
discovered services are cached. Queries, if not
answerable locally are propagated.
• The router and relay services maintain information
about routes to peers and translation between
various transport services.
• There are also security and authentication services
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.NET
• Microsoft views the next generation web as a
challenge to its control of the desktop
• .NET is Microsoft’s response
• .NET is a distributed peer to peer service
environment built on top of a series of interfaces
• Microsoft is aggressively upgrading their existing
software to include support for services
• Microsoft is very conscious of the need to promote
this new environment via killer applications
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Microsoft’s .NET
• .NET is built by extending and creating new
tools and services in three areas:
– A set of servers – both modified existing (SQL
and Exchange) and new (BizTalk)
– A set of tools – the wizards in VB and C++ are
extended to encompass web services
– New foundation services – advertising,
notification, and security (Passport) that are a
part of the CTM.
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The .NET Interfaces
• XML is the language or abstract syntax for
protocols in .NET
• SOAP is the envelop which will be used to
transmit the messages. It is used within an http
POST request to send a UDDI request or get a
WSDL interface.
• UDDI is the set of protocols to used to advertise,
find, and combine services. It is written in XML.
• WSDL is the set of protocols used to define web
services. It is written in XML.
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.NET Seduction
• Microsoft will help users see how this new environment
will work by building new devices and services
– New devices that consume services
• Xbox
• Tablet PC
• Smart phone
– User experiences that promote the new environment
• Office will be .Net sensitive
• Microsoft Project will be .Net sensitive
• XP will be .Net sensitive
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The Semantic Web
• Tim Berners-Lee has described the next
generation web as the semantic web.
• The semantic web would be manipulable by
programs
• Like the current web, his vision is one that:
– Is distributed and decentralized
– Must scale well and allow for imperfect contributions
– Must be such that the vast majority of the contributors
to the web can participate easily
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The Components
• XML provides an extensible language for
document and data interchange including
– Query
– Linking
• RDF provides a mechanism for developing:
– Descriptions of resources
– Descriptions of the descriptions (schema)
• Inference engines (agents) would have the ability
to discover resources based on schema analysis
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The Web Today
Web
Server
DN
Server
DN
Server
DN
Server
DN
Server
2. Object
Request
Client
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1. Location
Lookup
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The Web with Descriptions
Web
Server
1. Registration
DN
Server
Web
Server
DN
Server
LDAP
Server
DN
Server
DN
Server
3. The Rest
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2. Attribute/Value Request
and
Object/Location Response
Client
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LDAP
Server
Web
Server
Semantic Web
LDAP
Server
Web
Server
DN
Server
DN
Server
LDAP
Server
DN
Server
DN
Server
5. The Rest 2. Description
Client
Association
Schema
Server
3. Object Query
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Schema
Server
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Schema
Server
1. Schema
Registration
Schema
Server
4. Inferencing
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Issues(1)
• A simple request could involve hundreds versus 10’s of
network hops
– This would greatly increase bandwidth and the impact of network
delays
– Preprocessing (DNS lookup pre LDAP) could reduce steps
– A component view could ease the burden by dynamically passing
requests off
• Caching of information could greatly ease the burden
– Clients could cache schema and schema heads
– Schema servers could cache schema structures
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Issues(2)
• The appropriate level of logic and the
distribution of processing will be critical
– What expressive power should be allowed (at
what computational cost)
• Disjunction
• Negation
– What should the schema servers do?
– What can the directory servers do?
– What can the client do?
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Conclusions
• Infrastructure exists that can be used
• There are at least two visions operating
– A business service view -- .NET
– A personal agent view – the semantic web
– JXTA appears capable of serving both visions
• It is not clear whether:
– Any solution can be made simple enough
– A critical mass payoff can be achieved in reasonable
time
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