E-CommerceArchitecturesand Technologies

Rob Oshana

Southern MethodistUniversity

Anatomy of E-Business Functions

Distributed Computing

Distributed Computing• Computing is said to be "distributed"

when the computer programming and data that computers work on are spread out over more than one computer, usually over a network

• Computing prior to low-cost computer power on the desktop, was organized in centralized "glass houses" (so-called because the computers were often shown to visitors through picture windows)

Distributed Computing

• Modern enterprises are using a mix of desktop workstations, local area network servers, regional servers, Web servers, and other servers

Distributed Computing

• A popular trend has been client-server computing which is simply the view that a client computer can provide certain capabilities for a user and request others from other computers that provide services for the clients– (The Web's HTTP protocol is an

example of this idea.)

Client/Server Computing

What is Client/ServerComputing

The client–server model consists of three parts: • client - the active component that initiates a request• server - the passive component that returns a service• network - the media that enable the transmission of

requests and services

A request A request

Client

ServerA service

/Client

Server

A service

What are the Models of Client/Server Computing?

• The key is the leverage of computing power between Clients and the Server

How much work or how many functions are to be handled by the client versus its server

Major Components in Client/Server

• User Interface (I/O functions - Thin Client, WWW, Phone)

Functional Process (Business Rules)

DBMS (for data access and retrievals, networking, services)

User Interface (e.g., Browser, I/O routines)

Functional Obj. (e.g., Stored procedures/Triggers)

Data Mgmt (e.g., DB2, Oracle, SQL/Server)

Major Models for Client/Server Three-Tier Model

• Client requests its service via some pre-compiled modules (COM) to interact with data access software on the server

Client ServerAgent(COM)

Component Object Module(e.g., precompiled stored procedures)

3 Tier Client/Server

Third-Tier - Databases, Legacy Data

COM

SNAetc...

CORBA

Mid-Tier - HTTP, Biz Objects, Active Server Pages, Scripting

COM

HTTP

“Desktop” - Compound Documents, Controls, Scripting

Three-Tier Client/Server Model Data Mgmt

ClientDB Server

User Interface(e.g., Browsers)

Functions

Function Server

CommunicationNetwork

A New Trend in Object-oriented Client/Server - N-tier Model

N-tier Architecture

Back-end-tierSystem Server

Database ServerMail ServerGateway ServerDNS Server

x-tierBusiness COM

3rd-tierBusiness COM

2nd-tierBusiness COM

First tierClient Interface

Distributed Computing

• Most popular distributed object paradigms – Common Object Request Broker

Architecture (CORBA)– Distributed Component Object Model

(DCOM)– Java/Remote Method Invocation

(Java/RMI)

CORBA and ORBs

CORBA

• Common Object Request Broker Architecture

• Brokers requests for services from objects that may reside elsewhere on a network

• Provides location independence• Provides vendor and language

interoperability

CORBA

• Everything in the CORBA architecture depends on an Object Request Broker (ORB)– acts as a central Object Bus over which

each CORBA object interacts transparently with other CORBA objects located either locally or remotely

CORBA

• Since CORBA is just a specification, it can be used on diverse operating system platform– mainframes– UNIX boxes– Windows machines– handheld devices

• As long as there is an ORB implementation for that platform

CORBA Architecture

• Object Request Broker (ORB) is the most important component

• Object Services are the low-level services that must be available on all platforms in a distributed system (e.g., lifecycle)

CORBA Architecture

• Common Facilities are the commonly-found services in particular distributed systems (e.g., email, print queuing)

• Application Objects are the high-level applications themselves (e.g., spreadsheets, word processors, programmable controllers)

CORBA Architecture

CORBA ORB

CORBAApplications

CORBADomains

CORBAFacilities

CORBA Services

Object Request Broker

• A CORBA Object Request Broker (ORB) is the middleware that establishes the client-server relationship between objects

• Using an ORB, a client object can invoke a method on a server object that can be on the same machine or across a network

Object Request Broker

• The ORB intercepts the call and finds an object that can implement the request, pass it the parameters, invoke its method, and return the results

• CORBA, like SQL, provides both static and dynamic interfaces to its services

Object Request Broker

• The client does not have to know the object's location, its programming language, its operating system, or any other system aspects that are not part of an object's interface

• Also, the client and server roles are dynamic: an object on the ORB can act as either client or server, depending on the occasion

Communicating via ORBs

Local Host

JavaInterpreteror Browser

ClientApplet

Remote Host

ObjectImplementation

ORB

RequestRequest

Distributed Computing with CORBA

• The client application does not need to know whether the object resides on the same computer or on a remote computer elsewhere on the network

• The client application needs to know only two pieces of information– the object's name– how to use the object's interface

Distributed Computing with CORBA

• The ORB takes care of the details– locating the object– routing the request– returning the result

Features and Benefits

• Each object encapsulates the details of its inner workings and presents a well-defined interface, reducing application complexity

• The CORBA approach also reduces development costs, because once an object is implemented and tested, it can be used over and over again

Features and Benefits

• CORBA's platform independence lets you run and invoke the object from any platform; you can run an object from the platform that makes the most sense for that object

• CORBA's language independence lets you reuse existing code and leverage your existing programming skills

Features and Benefits

• CORBA is based on an open, published specification

• Implemented on and supported by numerous hardware and operating system platforms

• CORBA Java objects are portable– build objects on one platform and deploy them

on any other supported platform

Features and Benefits

• Interoperability. CORBA objects are fully interoperable because they communicate using the Internet Inter-ORB Protocol (IIOP)

• Software bridges enable communications between CORBA objects and objects developed using Microsoft's DCOM technology

Features and Benefits

• Modularity. CORBA objects interact via interfaces – developers can modify objects without

breaking other parts of the application– Changing an object's implementation

does not affect other objects or applications because that object's interface stays the same

Features and Benefits• Compatibility. CORBA protects your

investment in existing systems– You can encapsulate a legacy application,

module, or entry point in a CORBA IDL wrapper that defines an interface to the legacy code

• Security. CORBA provides security features such as encryption, authentication, and authorization to protect data and to control user access to objects and their services

CORBA Environment

Source: Netscape

CORBA in a Three Tier Architecture

Source: Netscape

Example

• Parcel-tracking application

• Suppose an Internet user wants to track delivery of a package

• From a browser, the user enters a URL that points to the delivery company's Web server

Source: Netscape

Example

• The server uses HTTP to send a Web page to the user– that page contains an embedded Java

applet, which is the client component of the parcel-tracking system

• So far, nothing is different from a traditional HTTP Web transaction

Example

• Next, the user enters a parcel-tracking number into the appropriate field in the Java applet

• Using the client-side ORB, the applet then generates and sends an IIOP message across the network, looking for a specifically-named server object that can obtain the status of the parcel

Example

• The ORB on the server with the appropriate parcel-tracking object picks up the message and invokes the object's status-finding method

• Through the server ORB, the object then generates another IIOP message looking for an object on a legacy system that contains all the parcel company's data

Example

• Upon obtaining the last request through its ORB, the mainframe containing the data-tracking object determines that status of the parcel from its database

• The mainframe returns an IIOP message with the information to the server object

Example

• The server then routes the information-again with IIOP and the ORBs-to the Java applet running on the client, which displays the results to the user

Example

Source: Netscape

COM

• COM (Component Object Model) is Microsoft's framework for developing and supporting program component objects

• It is aimed at providing similar capabilities to those defined in CORBA

COM• COM provides the underlying services of

interface negotiation, life cycle management (determining when an object can be removed from a system), licensing, and event services (putting one object into service as the result of an event that has happened to another object)

• COM includes COM+, DCOM, and ActiveX interfaces and programming tools

COM Principles

• Rigorous Encapsulation– Black box -- no leakage of implementation

details– All object manipulation through strict

interfaces

• Polymorphism– via multiple interfaces per class– “Discoverable”: QueryInterface COM

Object

IUnknown

IRobot

IDispatch

COM Architecture

ClientClient ComponentComponent

InprocessInprocess

COMCOMrun timerun time

providerproviderSecuritySecurity

RPCRPC

COMCOMrun timerun time

SecuritySecurityproviderprovider RPCRPC

LocalLocal

LPCLPCProtocol stackProtocol stack Protocol stackProtocol stack

DCOM network-DCOM network-protocolprotocol RemoteRemote

Source: Microsoft

Pluggable Transports

COMCOMClientClient

COM Runtime ArchitectureFlexible and extensible

Component

CO

M R

un

tim

e

Server MachineClient Machine

TCP, UDP

SPX,IPX

Net BUI

HTTP

“Falcon”CO

M R

un

tim

e

Proxy

Other Component

Source: Microsoft

The COM ArchitectureA scalable programming model

ClientClient ComponentComponent

In the same In the same process process Fast, direct Fast, direct

function callsfunction calls

ClientClient ComponentComponentCOMCOM

Client ProcessClient Process Server ProcessServer Process On the same On the same machinemachine Fast, secure IPCFast, secure IPC

Across machinesAcross machines Secure, reliable Secure, reliable

and flexibleand flexibleDCE-RPC based DCE-RPC based DCOM protocolDCOM protocol

COMCOMDCERPC

ClientClient

Server MachineServer MachineClient MachineClient Machine

COMCOM ComponentComponent

Source: Microsoft

DCOM

• DCOM which is often called 'COM on the wire', supports remoting objects

• A DCOM server is a body of code that is capable of serving up objects of a particular type at runtime

• DCOM server components can be written in diverse programming languages like C++, Java, Object Pascal (Delphi), Visual Basic and even COBOL

DCOM

• As long as a platform supports COM services, DCOM can be used on that platform

• DCOM is now heavily used on the Windows platform

ServerServerClientClient

COM/DCOMLets ActiveX components run anywhere

CO

MC

OM

Remote object onRemote object onany server any server

Object runningObject runningon clienton client

Object runningObject runningon clienton client

COM

Source: Microsoft

COMClient

Linux 2.0 (Intel)

BETA COM

HP/UX

COM

Digital Open VMS

COM

Siemens Nixdorf SINIX

COM

SCO UnixWare

COM

Digital Unix 4.0 (Alpha)RC

COM

IBM MVS 5.2.2 (OS390)

COM

IBM OS/400

COM

IBM AIX

COM

DCOM

Sun Solaris (Sparc) 2.5

RC COM Q3’97

Q3’97

Q1’98

H1’98

H1’98 H1’98

Q4’97

H1’98

H1’98

Q4’97

COM and DCOM

Source: Microsoft

ContainersContainers

Office BinderOffice BinderOffice BinderOffice Binder

MosaicMosaicMosaicMosaic

Internet ExplorerInternet ExplorerInternet ExplorerInternet Explorer

Windows ShellWindows ShellWindows ShellWindows Shell

Architecture Overview

Internet ExplorerInternet ExplorerInternet ExplorerInternet Explorer

HTMLHTMLHTMLHTML

VRMLVRMLVRMLVRML

WordWordWordWord

VisioVisioVisioVisio

MicroGrafxMicroGrafxMicroGrafxMicroGrafx

ActiveX documentsActiveX documents

HTMLHTMLHTMLHTML

VRMLVRMLVRMLVRML

MPEGMPEGMPEGMPEG

VRMLVRMLVRMLVRML

RealAudioRealAudioRealAudioRealAudio

HTMLHTMLHTMLHTML

ActiveX controlsActiveX controls

ShockwaveShockwaveShockwaveShockwave ODBCODBCODBCODBC

VRMLVRMLVRMLVRML HTMLHTMLHTMLHTML

Visual Basic Visual Basic ScriptScript

Visual Basic Visual Basic ScriptScript

JavaScriptJavaScriptJavaScriptJavaScript

REXXREXXREXXREXX

ActiveX scriptingActiveX scripting

PERLPERLPERLPERL

Visual BasicVisual BasicScriptScript

Visual BasicVisual BasicScriptScript

JavaScriptJavaScriptJavaScriptJavaScriptServicesServices URL resolutionURL resolutionHTTP, FTPHTTP, FTP

URL resolutionURL resolutionHTTP, FTPHTTP, FTP

HyperlinkingHyperlinkingHistoryHistory

FavoritesFavorites

HyperlinkingHyperlinkingHistoryHistory

FavoritesFavorites

Code downloadCode downloadand securityand security

Code downloadCode downloadand securityand security

COM+

• COM+ is an extension of COM

• COM+ is both an object-oriented programming architecture and a set of operating system service

• It adds to COM a new set of system services for application components while they are running, such as notifying them of significant events or ensuring they are authorized to run

COM+

• COM+ is intended to provide a model that makes it relatively easy to create business applications that work well with the Microsoft Transaction Server (MTS) in a Windows NT system

COM+• It is viewed as Microsoft's answer to the

Sun Microsystems-IBM-Oracle approach known as Enterprise JavaBeans (EJB)

• Among the services provided by COM+ are: – An event registry that allows components to

publish the possibility of an event and other components to subscribe to be notified when the event takes place

COM+

– The interception of designated system requests for the purpose of ensuring security

– The queueing of asynchronously received requests for a service

COM+COM+COM+ Services:COM+ Services:EventsEventsSecuritySecurityLoad Load Balancing Balancing Queued Queued ComponentsComponentsIn Memory In Memory Database DatabaseCompensatingCompensating ResourceResource ManagerManagerAdministrationAdministration

MTSMTS

MTS Services:MTS Services: TransactionsTransactions Resource PoolingResource Pooling SecuritySecurity AdministrationAdministration

COMCOMThe ModelThe ModelTools SupportTools SupportMulti-LanguageMulti-LanguageDiscovery (QI)Discovery (QI)

COM+COM+A caring, sharingA caring, sharing

environment forenvironment for youryourcomponentscomponents

COM+COM+A caring, sharingA caring, sharing

environment forenvironment for youryourcomponentscomponents

Technology Scenario

E-Business Servers

• E-Business functions can be processed by several servers in an e-business site– Arrive by browsers (B2C)– Generated by computers (B2B)

Servers of an E-Business Site

E-business site

client

Web server

SecureWeb server

Paymentserver

Applicationserver

Databaseserver

Anatomy of E-Server Transactions

• E-business functions implemented through client/server interactions– Client makes a request to a server

(primary server)– Possible help from secondary servers

• Execution is not deterministic– Request only sent to DB server if the

application server does not have the data

E-Business Functions and C/S Interactions

E-Business Function(e.g. Browse, Search, Pay)

1 2 n. . . .Client/Server Interactions

C/S Interaction

client web serverapplication

serverdatabase

server

C/S Interaction Diagram

• CSID is specified for each e-business function

• Represents all possible interactions for that function

• CSID structure– Nodes; represent visits to clients and/or servers

during execution• Square nodes; client nodes• Circle nodes; represent servers involved in the

implementation

– Arcs; represent probabilities and message types

CSID

C WS AS DB AS WS C

C

C

WS

1 2

3

4

5

6

7 8 9 10

[1,m1] [0.95,m3] [0.8,m6] [1,m7] [1,m8] [1,m9]

[0.05,m2][0.2,m4]

[1,m5]

C: clientAS: application serverDB: database serverWS: Web server

C/S Interactions

C WS

C

1 2

3

[1,m1]

[0.05,m2]

C WS AS DB AS WS C

1 2 4 7 8 9 10

[1,m1] [0.95,m3] [0.8,m6] [1,m7] [1,m8] [1,m9]

a. Interaction 1

b. Interaction 2

C WS AS

C

WS

1 2 4

5

6

[1,m1] [0.95,m3]

[0.2,m4]

[1,m5]

C/S Interactions

c. Interaction 3

Expanded CSID Notation

AS DB

[1.0,m9] [1.0,m10]

AS DB

[1.0,m11]

4 4.1 4.2 7

search

AS DB

WS

. . . . . .

4

7

5

[0.8,-] [1.0,m7]

[0.2,m5]

From CBMGs to CSIDs

• 1. Obtain the static CBMG• 2. From the static CBMG build a list of all

e-business functions• 3. For each business function, determine

the software servers (web server, app server, DB server, authentication server) involved in the execution– Document the relationship

From CBMGs to CSIDs

• 4. Determine the flow of messages between client and server and build a CSID for each business function

• 5. Estimate the message sizes for each of the messages in the CSID

• 6. Determine for each node of the CSID associated with an e-business function, the amount of resources of each type (processor, storage systems, etc) when the e-business function is executed

E-business function

Web Server

Trading Server

Authentication server

Application server

Database server

Login Register Search Select Browse Open account

Get quotes Get report View chart View indexes

Trade Create portfolio

Add to portfolio

Delete from portfolio

Asset planning

CBMG

Entry Home LoginAdd to

cartSelect

Browse

Search

Register

Pay

Search

CSID for E-Business function PAY

C AS PS TS C

C C

Resource usage for payment server- cpu time- number of I/Os