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Enterprise Resource Planning

Dr. Djamal Ziani

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CHAPTER 5

ENTERPRISE SYSTEMS ARCHITECTURE

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Outline

Examine the enterprise systems modules and architecture.

Understand the implication of good architecture on ERP implementation.

Know the various types of ERP architectures and the related benefits and drawbacks of each architecture.

Learn about the Service Oriented Architecture and its impact on ERP systems.

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Benefits to study Enterprise System Architecture

Help management and the implementation teams understand in detail the features and components of the enterprise system.

Provide a visual representation of the complex system interfaces among the ERP application and databases, operating systems, legacy applications, and networking.

Management can develop a better IT plan.

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Enterprise Systems Architecture (ESA) Model

Architecture categories

Two-tiers architecture

Three-tiers architecture

Service oriented architecture

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Two-tiers architecture

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The server handles both application and database duties

Two-tiers architecture

Benefits– Easy-to-use and access to information and services– Low cost in terms of infrastructure requirements– High performance with a limited number of workstations

Drawbacks– Inflexible in terms of adding more clients and software– Requires expensive middleware for integration– Changes or modifications in database affect applications– Limited flexibility in moving program functionality from one

server to another

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Three-tiers architecture

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•Data Tier (Data Management)•Business Tier (Business logic of functional modules)•Presentation Tier (End-User Interface—GUI)

Three-tiers architecture

Benefits– End-users have access to ERP applications over the Web.– Easily integrate ERP applications with existing systems.– Server-centric—No complex, expensive client software

installation.– Client-centric—Architecture has better response time because

user requests are mostly processed on the client’s computer. – Web-based architectures also allow better system-to-system

integration.

Drawbacks– Client-centric architectures lack security

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Example of Two-tiers architecture

SAP R/2 is mainframe solution and was first compact software package for the whole spectrum of business applications.

It runs on mainframes, such as IBM, Siemens, Amdahl. The current version of R/2 is 6.1.

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Example of Three-Tiers architecture

SAP R/3 is SAP' integrated software solution for client/server and distributed open systems.

SAP R/3 is the world’s most-used standard business software for client/server computing.

R/3 meets the needs of a customer from the small companies to multi-billion dollar companies.

The software is highly customizable using ABAP programming language.

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Service Oriented Architecture

Also known as object-oriented architectures for Web platforms

Breaks the business tier into smaller, distinct units of services, collectively supporting an ERP functional module

Allows message interaction between any service consumer and service provider

A consumer from a device using any operating system in any language can use this service.

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service-oriented architecture (SOA)

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Benefits of SOA

Business-level software services across heterogeneous platforms

Complete location independence of business logic

Services can exist anywhere (any system and any network)

Loose coupling across application services

Granular authentication and authorization support

Dynamic search and connectivity to other services

Benefits of SOA

Enhances reliability of the architecture

Reduces hardware acquisition costs

Leverages existing development skills

Accelerates movement to standards-based server and application consolidation

Provides a data bridge between incompatible technologies16

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Strong and use coupling

Strong coupling occurs when a dependent class contains a pointer directly to a concrete class which provides the required behavior.

Loose coupling occurs when the dependent class contains a pointer only to an interface, which can then be implemented by one or many concrete classes.

Loose coupling provides extensibility to designs. A new

concrete class can easily be added later that implements that same interface without ever having to modify and recompile the dependent class. Strong coupling does not allow this.

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loose coupling

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Drawbacks of SOA

SOA implementations are costly and time-consuming

Requires complex security firewalls in place to support communication between services

Performance can be inconsistent

Requires enterprise-level focus for implementation to be successful

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SAP eSOA

Enterprise SOA is SAP's business oriented version of SOA (Service-Oriented Architecture) and SAP’s blueprint for developing flexible and services based business solutions.

ESOA enables the rapid composition of business solutions by encapsulating business logic and expose it as enterprise services

ESOA supports reassembling smaller functionality components and to develop new innovative business solutions that meet ever changing business requirements.

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SAP eSOA

eSOA = ES (Enterprise Service) + SOA

Enterprise SOA provides business with an IT strategy and a top-down approach to define enterprise services and also to guide the deployment of Web services at a business process level.

Enterprise Service (ES)

It is a service which provides business functionality and which is published by SAP in the enterprise services workplace in the SAP Developer Network (SDN)

Enterprise services have the following Business semantics: – The model is based on process components, business

objects and global data types (GDTs)

– based on open standards. The interfaces are described according to WSDL22

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SAP Enterprise Architecture framework

Runtime Architecture Overview

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HTTP Communication Layer

at SAP, all SOAP messages are sent via HTTP

The main task of the layer is to accept incoming HTTP requests and dispatch them to the appropriate receiver.

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Web Service Enabling Layer

receives HTTP-based SOAP messages from the HTTP Communication Layer

It interprets the SOAP messages and extracts the parameters for calling a Web service.

The layer contains the Web service proxies, which are the implementation components that implement the Web service interface by forwarding calls to existing mySAP applications.

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Web Service Enabling Layer

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Categories of web services

Synchronous service: the client invoking a service and then waiting for a response to the request. Because the client suspends its own processing after making its service request, synchronous services are best when the service can process the request in a small amount of time.

Asynchronous service: the client invokes the service but does not -- or cannot -- wait for the response. Often it may take a significant amount of time for the service to process the request.28

Synchronous Web Services

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Processes of Synchronous Service

Dispatching a request (steps 1–3)

Processing a request (steps 4–5)

Sending a response (steps 6–8)

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Dispatching a request

The Internet Communication Manager (ICM) decides whether to forward an incoming request to the ABAP stack or the Java stack (base on URL part)

The Internet Communication Framework (ICF) receives all HTTP requests which are sent to the ABAP stack and forwards the request to the appropriate application.

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Processing a request

Reads the information in the SOAP header and extracts the Web service data from the body of the message.

The extracted XML Web service data is forwarded to the proxy framework.

The proxy framework maps the data from XML to ABAP data structures and invokes the appropriate Web service proxy.

local calls to function modules, BAPIs and RFCs of mySAP applications

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