©Ferenc Vajda 1 Open Grid Services Architecture Ferenc Vajda vajda@sztaki.hu Computer and...

©Ferenc Vajda

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Open Grid Services Architecture

Ferenc Vajdavajda@sztaki.hu

Computer and Automation Research Institute

Hungarian Academy of Sciences

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©Ferenc Vajda

GRID

Past: Globus

Present: OGSA

Future: Semantic Grid

“Past is history, future is mystery”

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Roots of OGSA

Globus Toolkit: GTPL (Globus Toolkit Public License)GT3: Platform Globus (Commercially supported)

“The Anatomy of the Grid”

“The Physiology of the Grid” papers by Ian Foster et al.

Grid Forum GGF (Global Grid Forum)

OGSA Working Group

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Main issues of “The Anatomy of the Grid”

-SDK (Software Development Kit)

• Virtual Organization (VO)

• Nature of Grid Architecture

-Interoperability

-Protocol

-Services

-API (Application Programming Interface)

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-Applications

Main issues of “The Anatomy of the Grid” 2.

• Architecture Description

-Fabric: interfaces to local control

-Connectivity: communicating easily and securely

-Resource: sharing single resources

-Collective: coordinating multiple resources

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The layered Grid architecture

“The Anatomy of the Grid”

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Main issues of “The Physiology of the Grid”

-Business-to-Business (B2B) Computing

-Web Serviceso SOAP

o WSDL

o UDDI

o WSFL

o WS-Inspection

• Grid technologies

-Enterprise Computing

-Service Providers (SPs)

• Background

-Globus Toolkit

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Building an Open Grid

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OpenStandards

Building an Open Grid

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OpenStandards

OpenSource

Building an Open Grid

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OpenStandards

OpenSource

OpenInfrastructure

Building an Open Grid

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OpenStandards

OpenSource

OpenInfrastructure

OpenGrid

Credit to Ian Foster

Building an Open Grid

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Incr

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Time

Customsolutions

Open GridServices Arch

GGF: OGSI, …(+ OASIS, W3C)

Multiple implementations,including Globus Toolkit

Web services

Globus Toolkit

Defacto standardsGGF: GridFTP, GSI

X.509,LDAP,FTP, …

App-specificServices

Grid and Open Standards

Credit to Ian Foster

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Open Grid Services Architecture

-Language interoperability

From Web Services

Standard interface definition mechanisms

-Interface and implementation

(multiple protocol bindings)

-Local/remote transparency

-Service semantics

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Open Grid Services Architecture 2.

• Further services: resource management, authorization, etc.

From Grids

• Lifecycle management

• Reliability and security models

• Discovery

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Open Grid Services Architecture 3.

• Objective: to integrate services across

- distributed

- heterogeneous

- dynamic virtual organizations

• Solution:

-standard mechanisms for creation, naming, discovery

-location transparency, multiple protocol binding

-integration with hosting environment

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OGSI

TransportProtocolHosting EnvironmentHosting Environment

Host. Env. & Protocol Bindings

OGSA Platform services: registry,authorization, monitoring, data

access, etc., etc.

More specialized &domain-specific

services

Models for resources &

other entitiesO

therm

odels

Environment-specificprofiles

Domain-specificprofiles

OGSAPlatform

GWD-R (draft-ggf-ogsa-platform-3) Editors:Open Grid Services Architecture Platform I. Foster, Argonne & U.Chicagohttp://www.ggf.org/ogsa-wg D. Gannon, Indiana U.

OGSA Platform

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Principal elements of OGSA Platform

• Open Grid Services Infrastructure (OGSI)

• OGSA Platform Interfaces

• OGSA Platform Models

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OGSA Platform Profiles

• Sets of domain-specific services

Environment, domain-specific supplements:

• Protocol bindings

• Hosting environment bindings

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Open Grid Services Infrastructure

•Service group

Key Features:

• Grid Service description and instances

• Service state, metadata and introspection

• Naming and name resolution

• Fault model

• Lifecycle

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OGSI

OGSI = Grid Technologies + Web Services

In OGSI everything is represented as a Grid service.

Service: a network-enabled entity that provides some capabilities through the exchange of messages.

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OGSI

Most important components:

•Grid Service

• Factory

• Registry

• HandleMap

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The Grid Service

-Grid service instance

• A WSDL-defined service that conforms to a set of conventions relating to its interface and behaviors.

•Description composed of two parts:

-Grid service description

-Describes a client’s interaction with service instances:syntax and semantics (PortType)

-Can be used by any number of Grid service instances

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The Grid Service 2.

-Has one or more Grid Service References (GSRs)

-Grid service instance

-Embodies a state

-Has one or more unique Grid Service

Handles (GSHs)

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The Grid Service 3.

•GSR (Grid Service Reference): abstraction for e.g. protocol binding, network address, etc.

•typed (characterized by the offered capability)

•interfaces (set of operations)

• invocation (by sequences of message exchange)

•created/destroyed (dynamically)

•GSH (Grid Service Handle): globally unique name

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Factories: Creating Transient Services

Factory = Factory interface + implemented service

CreateService operation: -creates a requested Grid service

-returns a GSH + an initial GSR

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Handles and References

-returns a valid GSR

• GSH: reference for service instance “forever”

• GSR: changes during lifetime

HandleMap: handle-to-reference mapper

-takes a GSH

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Registry and Notification

Semantics: protocol binding property

e.g. SOAP/HTTP protocol

Registry: registry interface + service data elements

(info about GSH)

Notification

Subscribe operation

NotificationSource interface

NotificationSink: message (“keep alive”)

“push” model (FindServiceData “pull” model)

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Client runtime architecture

Credit to S. Tuecke et al. (Grid Service Specification)

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GSH Resolving

Credit to S. Tuecke et al. (Grid Service Specification)

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Open Grid Service Infrastructure

Implementation

Servicedata

element

Other standard interfaces:factory,

notification,collections

Hosting environment/runtime(“C”, J2EE, .NET, …)

Servicedata

element

Servicedata

element

GridService(required)

Dataaccess

Lifetime management• Explicit destruction• Soft-state lifetime

Introspection:• What port types?• What policy?• What state?

Client

Grid ServiceHandle

Grid ServiceReference

handleresolution

Credit to Ian Foster

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1a. Request to Registry for sources of data about “x”

1b. Registry responds with

Factory handle2a. Request to Factory for access to database

2b. Factory creates GridDataService to manage access

2c. Factory returns handle of GDS to client

3a. Client queries GDS with XPath, SQL, etc

3b. GDS interacts with database

3c. Results of query returned to client as XML

SOAP/HTTP

service creation

API interactions

Registry

Factory

Grid Data Service

Client

XML / Relational database

OGSA-DAI (Data Access and Integration

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Security Challenges

Integrate

Extensible architecture

Using existing services

Implementation agnostic

Interoperate

Secure interoperability

Publishing QoS

Federation

Trust

Trust relationship

Trust establishment

Presumed trust

Assertions

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Grid Security Requirements

• Integrity

• Authentication• Delegation• Single sign-on

• Credential lifespan and renewal

• Authorization

• Privacy

• Confidentiality

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• Securing infrastructure

Grid Security Requirements 2.

• Policy exchange

• Secure logging

• Assurance

• Manageability

• Firewall traversal

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Components of Grid Security Model

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Security Architecture Building Blocks

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Security as Service

• Privacy service

• Authentication service

• Identity mapping service

• Authorization service

• I/O policy service

• Credential conversion service

• Audit service

• Profile service

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Semantic Grid

Ferenc Vajda

vajda@sztaki.hu

Computer and Automation Research Institute

Hungarian Academy of Sciences

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Data/Information/Knowledge

Data: observed facts

Information: organized and related facts with attributed properties

Knowledge: “sum of what is known”: concepts, objects with characteristics, principles, laws, know-how, etc.

Semantics: a term used for meaning, interpretation, knowledge through reasoning

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Different Evaluations of the Grid

1. Grid generations

• To link supercomputer centers

(e.g. I-way)

• Toolkit- and middleware-based

(e.g. Globus)

• Service-oriented (OGSA)

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Different Evaluations of the Grid 2.

2. Based on the technologies used

• Protocol-based

• Service-based

• Semantic Web based

3.Based on application requirements

• Data/computational Grid

• Information Grid

• Knowledge Grid

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Problems Related to Semantic Web

• Knowledge Evaluation

• Knowledge Representation

• Ontologies

• Agents

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Resource Description Framework (RDF)

-Set of triplets: subject, property,object

• Metadata: structured data about data

• Resource identification: Universal Resource Identifier (URI)

• Most common type of URI: Uniform Resource Locator (URL)

• Qualified URI: URI + fragment identifier

• Concepts:

-Graph model

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RDF 2.

Subject ObjectProperty

-Data types: based on XML Schema

-Vocabulary: URI-based (Both nodes and arcs)

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RDF 3.

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What is an Ontology?

Greek: ontos = being, logos = science

• world view regarding a domain

• shared understanding

• definitions, inter-relationship

• conceptualization

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What does an Ontology look like?

• vocabulary of terms

• specification of their meaning (i.e. definitions)

- highly informal (natural language)

- semi-informal (restricted, structured form of natural language)

- semi-formal (artificial, formally defined language)

- rigorously formal (formal semantics, proofs, completeness)

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Use of Ontologies

• communication (between people and organizations)

• system engineering (specifications, reusable components)

• inter-operability (between systems)

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Ontologies

• Web Ontology Language (OWL)

• Ontology: defines the terms used to describe and represent an area of knowledge

-taxonomy: object classification + relationship among them (properties and inheritance of properties)

-inference rules

• DAML (DARPA = Defense Advanced Project Agency

Agent Markup Language)

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Agents

Agent: Capability to understand and integrate diverse information resources (based on domain ontologies)

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Agents 2.

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Semantic Web Layers

Credit to Berners-Lee (XML2000 address)

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Semantic Grid

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Semantic Grid

Basis:

• Metadata enabled

Goal:

Grid + Semantic Web

• Ontologically principled

New e-Science infrastructure

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Services

e.g. -semantic database integration

-semantic workflow description

• Base services

-data/computational services (network access, resource allocation and scheduling, data shipping, etc.)

-information services (queryprocessing, event notification, instrumentation management,

etc.)

• Semantic services

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Services 2.

-application

• Knowledge services

-acquisition

-modeling

-publishing, use and maintenance

-resource management

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Knowledge Grid Architecture

Credit to Carole Goble et al.

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Roles of Ontologies

Credit to Carole Goble et al.

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The term ‘procedure’ used by one tool is translated into the term ‘method ‘ used by the other via the ontology, whose term for the same underlying concept is ‘process’. procedure

viewer

translator

Ontology

method

library

give me the procedure for…

translator

here is the

METHOD for…

procedure = ???

procedure =

process

give me the

process for…

here is

the process for…METHOD =

process

??? = process

Roles of Ontologies (Example)

Credit to Rokhlenko Oleg

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Knowledge Services

Credit to Carole Goble et al.

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Typical Applications

• Service discovery

• Knowledge annotation

• Workflow composition

• Data interpretation

• Collaborative science

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Grid Service Discovery

Simple discovery

• attribute-base

• name lookup

• type matching

Semantic discovery

• matchmaking

• based on ontology description

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Brokering vs. Matchmaking

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Grid Service Discovery Framework

Ontology based description used by• service provider

• service requester

• service matchmaker

• service registry database

Matchmaking process

• comparison: request to registry

• decision: based on filters

• information

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Service Description

“What the service does”: service profile

“How it works”: ServiceModel

“How it is used”: ServiceGrounding

Description by RDF(S): Resource Description Framework Schema

Service profile

• description (human readable)

• functionalities

• functional attributes

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Service Description 2.

Credit to DAML-S White Paper

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Filtering

Independent filtering is based on

• context matching

• syntactic matching

- comparison of profiles

- similarity matching

- signature matching

• semantic matching

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myGrid project

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Role of Ontologies in myGrid