Web Services. Overview Why Web Services What’s Web Services Web Services Framework insfrastructure

Web Services

Overview

Why Web Services What’s Web Services Web Services Framework insfrastructure

Why Web Services?

Example Problem Space

ClientPO Service

Credit Service

Inventory Service

Purchase Order

Credit

Check

ReserveInventory

Credit

Response

InventoryResponse

InvoiceConsolidate

Results

Early (Internet) Technologies

SMTP/MIMEe-mail is still the killer app

FTP, NNTPHTTP/HTTPS, HTML

the protocol behind Internet’s popularity

Most of these facilitated app to human interaction

over the Internet/intranet

Early (intranet) Technologies

DCE from OSF -- RPC based, procedural ORB -- object oriented, mostly synchronous

CORBA, COM/DCOM from Microsoft, Java RMI/EJBs

MOM -- message oriented, synchronous as well as asynchronous JMS ( Java API standard ) Many proprietary implementations

Most of these facilitated app2app interaction within atrusted intranet and without much consideration to interoperability across different implementations.

Today’s Web

Web designed for application to human interactions Served very well its purpose:

Information sharing: a distributed content library. Enabled B2C e-commerce. Non-automated B2B interactions.

How did it happen? Built on very few standards: http + html Shallow interaction model: very few assumptions made about

computing platforms. Result was ubiquity.

The issue: Unleashing B2B (and G2B!) As mentioned above, most Web apps are for business-to-consumer (B2C):

person at browser Still too hard to build distributed applications that connect businesses Risk losing customers if you provide URL links to a partners' website

Business-to-business (B2B) apps have been highly touted, but suffered for the following reasons: Isolation of business processes because of incompatible systems

Microsoft's DCOM, Sun J2EE's Bridges available but app server vendor specific

Solutions were too costly or too complex to implement Business relationships change such as mergers and acquisitions Accelerated pace of change in technology and standards

ASP 2.0, ASP 3.0, ASP.NET EJB 1.0, EJB 1.1, EJB 2.0

Need a simple, standard framework for B2B applications

What’s next?

The Web is everywhere. There is a lot more we can do! E-marketplaces. Open, automated B2B e-commerce. Business process integration on the Web. Resource sharing, distributed computing.

Current approach is ad-hoc on top of existing standards. e.g., application-to-application interactions with HTML forms.

Goal:

enabling systematic application-to-application interaction on the Web.

The Web Services Way

Web Services standards (SOAP, WSDL, … ): based on widely accepted Internet friendly technologies

(HTTP/HTTPS, XML, …), are mostly orthogonal to each other and enjoy broad support from vendors

Web Services: Network accessible programs, expose functionality by receiving/sending SOAP messages

over HTTP/HTTPS, and describe this interface as WSDL descriptions.

App2App Interaction -- the Web Services Way

Transport protocol HTTP/HTTPS

Data Encoding SOAP (Simple Object Access Protocol), XML Schema

Interface Description WSDL (Web Services Description Language)

Service Description and Discovery UDDI (Universal Description, Discovery and

Integration) Security

WS-Security, XML-Signature, XML-Encryption, ...

What’s a Web Service?

“Web services” is an effort to build a distributed computing platform for the Web.

Yet another one!

What’s a Web Service? A web service is a software component

Exposes a business function/service/chunk of data Can be accessed by another application over Internet Messages are exchanged using a standard XML format

Application Server (J2EE or .NET)

Business logic

Web Service

Web Application

BusinessBusiness

AgencyAgency

<xml>

<xml>

<html>

<html>

What’s a Web Service? A program programmatically accessible over

standard internet protocols

Loosely coupled, reusable components

Encapsulate discrete functionality

Distributed

Add new level of functionality on top of the current web

Web Services Model

Web service applications are encapsulated, loosely coupled Web “components” that can bind dynamically to each other

Web Services Model

Language and platform independent =>separation of specification and implementation

Loosely coupled => message based, synchronous and asynchronous interactions.

Over the Internet =>No centralized control, use of established protocols, security considerations.

Inter-operable =>Standards based.

How Web Services Helps Cross-platform, cross-language support

Java, .NET, PHP, Perl, Python Based on industry standards (W3C)

Catches the XML wave XML, SOAP, WSDL, UDDI

Supported by many vendors Unlike CORBA

Relatively easy to implement Service publication and lookup

Conduct business without prior relationship Loosely coupled

Low demands on network quality Based on request/response model

Enables public/private cooperation on information products

Web Services Framework



Framework can be described in terms of

What goes “on the wire”: Formats and protocols.

What describes what goes on the wire:Description languages.

What allows us to find these descriptions:Discovery of services.

The Web Services StackWire

ProtocolsDescription Discovery

TCP/IP

HTTP/SMTP/BEEP

XML

SOAP/XMLP

SOAP Blocks

XML

WSDL

WSDL Extensions

Process

Agreements

Inspection

Registry (UDDI)

The Web Services Stack helps us understand how each of the various pieces fit into the “Big Picture”

The Web Services Stack

Wire Protocols Primary Role: provide a standard, flexible

communications channel Secondary Role: provide a standard, flexible wire-

level data representation

Advantage: interoperability at the lowest level


Description Primary Role: provide a standard, flexible way to

describe what and how a Web service does what it does.

Advantage: interoperability


Discovery Primary Role: provide a standard, flexible way to

discover where a Web service is located and where to find more information about what the Web service does (the description)

Advantage: interoperability, dynamic integration

WS-Resource Framework Capabilities

Specifies how to use XML to describe and access a resource’s properties

Clarifies how stateful resources are addressedDefines how a resource is created and messages to

destroy resourcesProvides a message subscription and notification

mechanism for Web services Outlines how to organize groups of resources and

services Adds a fault tolerance capability to WS-Addressing Defines a standard, extensible format for Web

services error messages

Web Services and Stateful Resources

“State” appears in almost all applications Data in a purchase order Current usage agreement for resources on a grid Metrics associated with work load on a Web

server There are many possible ways Web services

might model, access and manage state The WS-Resource framework proposes to

standardize this capability for Web services

Inte

rface

WebService

The WS-Resource framework model

Web Service

WSDLRun-time environment

Inte

rface

WebService

message

message

Invoking a Web Service

address

Endpoint Reference

Run-time environment


What is a WS-Resource Examples of WS-Resources:

Physical entities (e.g.. processor, communication link, disk drive)or Logical construct (e.g.. agreement, running task, subscription)

Real or virtual

Static (long-lived, pre-existing) orDynamic (created and destroyed as needed)

Simple (one), or Compound (collection)

Unique - Has a distinguishable identity and lifetime

Stateful - Maintains a specific state that can be materialized using XML

May be accessed through one or more Web Services

resource


context

Inte

rface

WebService

messageid

message

Using a Web service to access a WS-Resource

id

address

resource


Endpoint Reference


context

Inte

rface

WebService

messageid

message

Using a Web service to access a WS-Resource

id

address

resource

resource

Endpoint ReferenceEndpoint Reference



Inte

rface

WebService

message

message

Creating / Locating a WS-Resource

address

Endpoint Reference

resource

Endpoint Reference

Web Service either locates or creates a

WS-Resource

address

id



IBM

WS-Resource Properties Resource state and metadata “Projected” as an

XML document Query and Set operations

WS-Resource LifeTime Explicit destruction or

“Soft state” time-to-live Provides for cleanup

of resource instances

resource

<ProcessorProperties><ProcID>5A34C1DE03</ProcID><ProcArchitecture>Power6.2</ProcArchitecture><ProcSpeedMIPS>400</ProcSpeed><ProcCacheMB>256<ProcCache><ProcRunning>1</ProcRunning>

</ProcessorProperties>


Architecture rationale WS-Resource framework exploits WS-Addressing

Web services and WS-Resources are referenced using an “Endpoint Reference”

Services that create or locate WS-Resources returnEndpoint References

Web service and WS-Resource are separate: A Web service is stateless A WS-Resource provides a context for stateful

execution Different entities, different lifetimes, different

capabilities


Web Services Infrastructure

Language and platform independent infrastructure for loosely-coupled, inter-

operable, app2app communication over the Internet.

Additional Web Services Infrastructure Components

Key Management (Security) XKMS

Web Services Management OMI (Open Management Interface)

...

Interesting thing to note is that these

are Web Services in themselves

XML Messaging: SOAP XML based protocol for

exchange of information Encoding rules for datatype

instances Convention for representing

RPC invocations Designed for loosely-

coupled distributed computing No remote references

Used with XML Schema Transport independent SOAP with Attachments

allow arbitrary data to be packaged.

SOAP1.1 MessageStructure

SOAPEnvelope

HeaderEntries

[Header Element]

Body Element

[FaultElement]

XML Messaging: SOAP

SOAP 1.1 defined: An XML envelope for XML messaging,

Headers + body An HTTP binding for SOAP messaging.

SOAP is “transport independent”. A convention for doing RPC. An XML serialization format for structured data

SOAP Attachments adds How to carry and reference data attachments using in a

MIME envelope and a SOAP envelope.

The SOAP Envelope

<SOAP-ENV:Envelope xmlns="http://schemas.xmlsoap.org/soap/envelope/">

< SOAP-ENV:Header> ... </ SOAP-ENV:Header>

< SOAP-ENV:Body> ... </ SOAP-ENV:Body> ...</ SOAP-ENV: Envelope>

What goes on the wire

Internet-scale integration needs a lingua-franca XML messaging protocol

over HTTP: SOAP

Intra-enterprise integration needs to allow alternates: CORBA, RMI Messaging In-memory method calls

SOAP SOAP

SecuritySecurity

AttachmentsAttachments

ReliabilityReliability

RoutingRouting

TransactionsTransactions

ContextContext

W3C

Descriptions: Meta-data

Integration requires interoperable machine-understandable descriptions

Enables dynamic, delayed binding of components.

Language extensibility provides support for different levels of application integration.

InterfaceInterface

Service QoS Service QoS

ServiceService

Public FlowsPublic Flows

Flows and Composition

Flows and Composition

AgreementsAgreements

WS

DL

WS

FL

XML SchemaXML Schema

Web Services Description Language

Provides functional description of network services: IDL description Protocol and deployment details Platform independent description. Extensible language.

A short history: WSDL v1.0, 9/2000 WSDL v1.1 submitted to W3C 3/2001. A de facto industry standard.

WSDL - Overview

A WSDL document describesWhat the service can doWhere it residesHow to invoke it

WSDL are like IDL but lot more flexible and extensible

Defines binding for SOAP1.1, HTTP GET/POST and MIME

WSDL descriptions can be made available from an UDDI registry

WSDL - Overview

WSDL is a simple XML grammar for describing how to communicate with a Web service It defines the messages (both abstract and concrete) that

are sent to and from a service It defines logical collections of messages (“port type”,

“interface”) It defines how a given “port type” is bound to particular

wire protocols It defines where the service is located

WSDL Overview

WSDL is extensible. WSDL was created by IBM and Microsoft

The intent was to create something that worked, not something that was complete

Creating a formal Web Services “data model” was not a priority

WSDL is RDF-compatible (not RDF-compliant)

WSDL Structure

WSDL1.1 DocumentStructure

WSDLDocument

[Types]

{Messages}

{Port Types}

{Bindings}

{Services}

WSDL Structure

portType Abstract definition of a

service (set of operations) Multiple bindings per

portType: How to access it SOAP, JMS, direct call

Ports Where to access it

Service

Port(e.g. http://host/svc)

Binding(e.g. SOAP)

Abstract interface

portType

operation(s)

inMesage outMessage

Port

Binding

WSDL - example<definitions>

<types>  </types>

<message name=“getQuote_In” />

<message name=“getQuote_Out” />

<portType name=“StockQuoteServiceInterface”>

<operation name=“getQuote”>

<input message=“getQuote_In” />

<output message=“getQuote_Out” />

</operation>

</portType>

<binding name=“StockQuoteServiceBinding” type=“StockQuoteServiceInterface”>

<soap:binding transport=“http://schemas.xmlsoap.org/soap/http” />

…

</binding>

<service name=“StockQuoteService”>

<port name=“StockQuoteServicePort” binding=“StockQuoteServiceBinding”>

<soap:address location=“http://www.acme.com/services/stockquote” />

</port>

</service>

</definitions>

Definition of data types

Definition of messages

Definition of port type

Definition of the bindings

Definition of the service

Using WSDL

1. As extended IDL: WSDL allows tools to generate compatible client and server stubs. Tool support for top-down, bottom-up and “meet in the

middle” development.2. Allows industries to define standardized service interfaces.3. Allows advertisement of service descriptions, enables dynamic

discovery and binding of compatible services. Used in conjunction with UDDI registry

4. Provides a normalized description of heterogeneous applications.

Client Proxy object

RMI-IIOP

JMS/MQ

SOAP/HTTP

Client invocation

Single stub can invoke services over different bindings Depends only on abstract

interface. Are independent of binding (but

pluggable). Add new bindings without

recompiling/redeploying stub Allows optimisations based on

the bindings of service. Will support extended services

models if described In WSDL

WSFL Overview

WSFL describes Web Service compositions.1. Usage patterns of Web

Services: describes workflow or business processes.

2. Interaction patterns: describes overall partner interactions.

A

B

C

[ WS]

[ WS]

WSFL Flow Models

Activities represent units of processing.

Flow of data is modeled through data links.

[ WS]

Activities can be mapped to the flow interface

Control links define execution flow as a directed acyclic graph

Activities are associated with specific typed service providers

Using Flow Models

“Public flows” provide a representation of the service behavior as required by its users.

Typically, an abstraction of the actual flow begin executed Defines a “behavioral contract” for the service. Internal implementation need not be flow-based. Flows are reusable: specify components types, but not what specific

services should be used!

“Private flows” are the flows executed in practice. WSFL serves as a “portable flow implementation language”

Same language is used in WSFL to represent both types of processes.

Global Models

Global models describe how the composed Web Services interact. RosettaNet automated. Like an ADL.

Interactions are modeled as links between endpoints of two service interfaces (WSDL operations).

An essentially distributed description of the interaction.

A

B

C

Discovery: Finding Meta-data

Static binding requires service “libraries”.

Dynamic binding requires runtime discovery of meta-data

InspectionInspection

DirectoryDirectory

ADS,DISCO

UDDI

UDDI Overview

UDDI is: A Web Services API for publishing and

discovering the existence of Web services A registry for managing information about Web

services A coalition of organizations working together to

manage UDDI registries and to further develop the Web Services API for accessing those registries.

UDDI Overview

UDDI is built around a “Yellow-pages” like data model:

Business Entity

Business Services

Service Bindings

Categories

Identities

TModels

UDDI Overview

TModel = “Technology Model”

TModel TModel Instance

Abstract metadata definition relating to some aspect of the UDDI registration

Implementation specific metadata conforming to a given TModel.

TModel = Abstract Class

UDDI Overview TModels

Categories & Identifiers Categorization and Identification taxonomies are TModels Categories and Identifiers are TModel Instances Keyed Referenced

Name + Value + TModel Examples: NAICS, UNSPSC, D&B #

WSDL Port Types WSDL Port Types are TModels WSDL Services that are bound to a Port Type are TModel Instances

WSFL Business Processes WSFL Flow Models are TModels WSFL Global Models are TModel instances

TModels represent the extent of UDDI’s semantic description capabilities.

UDDI Overview

UDDI has only limited extensibility through TModels

UDDI was created by IBM, Microsoft and Ariba (many companies have joined the effort)

The intent was to put something together that worked.

UDDI Overview

UDDI Version 1.0 – September 2000 (in production)

UDDI Version 2.0 – June 2001 UDDI Version 3.0 - In development

UDDI will be presented to a standards body after Version 3.0

UDDI Overview

UDDI defines the operation of a service registry: Data structures for registering

Businesses Technical specifications: tModel is a keyed reference to a

technical specification. Service and service endpoints: referencing the supported

tModels SOAP Access API Rules for the operation of a global registry

“private” UDDI nodes are likely to appear, though.

UDDI RelationshipsWeb Service

Web Service

SIC CODENAICS

DUNS NumbersThomas Registry ID

Rosetta-NetBASDA

Simple.Buy

Schemas,Interchange specification

businessEntitybusinessEntitybusinessEntity

businessServicebusinessService

bindingTemplatebindingTemplateInstanceDetailsInstanceDetails

categoryBagkeyedReferencekeyedReference

identifierBagkeyedReferencekeyedReference

tModels

WS-Notification

WS-NotificationBrings enterprise quality publish and subscribe messaging to Web services

Loosely coupled, asynchronous messaging in a Web services context

WS Notification exploit WS Resource framework and Web services technologies

Subscriber indicates interest in a particular “Topic” by issuing a “subscribe” request

Broker (intermediary) permits decoupling Publisher and Subscriber

“Subscriptions” are WS-Resources

Various subscriptions are possible

Publisher need NOT be a Web Service

Notification may be “triggered” by:WS Resource Property value changesOther “situations”

Broker examines current subscriptions Brokers may

“Transform” or “interpret” topicsFederate to provide scalability

Broker

Subscriber

WS-Notification

Publisher

subscribe

subscribe

S S S

notify

notify

notify

notify

WS-Notification Characteristics of WS-Notification:

Web services integration of traditional enterprise publish/subscribe messaging patterns

Composes with other Web services technologies Facilitates integration between different messaging

middleware environments Standardizes the role of Brokers, Publishers, Subscribers and

Consumers Provides two forms of publish/subscribe:

direct publishing and brokered publishing Standardizes Web service message exchanges for publishing,

subscribing and notification delivery Defines XML model of Topics and TopicSpaces to categorize

and organize notification messsages

A

ServiceLevel

WS-Resource framework & WS-NotificationScenario: Grid Resource Management & Scheduling

Cluster

RRR

Mainframe

RRRIBM

IBM

Blades

RRR

Notification

GridScheduler

WS-Resource used to “model” physical

processor resources

WS-Resource Properties “project” processor status (like utilization)

Local processor manageris “front-ended” with A Web service interface

Other kinds of processors are also

“modeled” as same type of WS-Resources

JJ

J

WS-Notification can be used to “inform” the scheduler when processor utilization

changes

Grid “Jobs” and “tasks” are also modeled using

WS-Resources and Resource Properties

Grid Scheduler

is a Web Service

Service Level Agreement

is modeled as a WS-

Resource Lifetime of SLA Resource tied to the duration

of the agreement

Documents

Web Services. Overview Why Web Services What’s Web Services Web Services Framework insfrastructure