Enterprise Resource Planning
Dr. Djamal Ziani
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CHAPTER 5
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ENTERPRISE SYSTEMS
ARCHITECTURE
Outline
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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.
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
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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
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Benefits
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Drawbacks
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Easy-to-use and access to information and services
Low cost in terms of infrastructure requirements
High performance with a limited number of workstations
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
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
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Benefits
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Drawbacks
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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.
Client-centric architectures lack security
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.
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The software is highly customizable using ABAP
programming language.
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
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A consumer from a device using any operating system in
any language can use this service.
service-oriented architecture (SOA)
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Benefits of SOA
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Business-level software services across heterogeneous
platforms
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Complete location independence of business logic
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Services can exist anywhere (any system and any
network)
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Loose coupling across application services
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Granular authentication and authorization support
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Dynamic search and connectivity to other services
Benefits of SOA
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Enhances reliability of the architecture
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Reduces hardware acquisition costs
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Leverages existing development skills
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Accelerates movement to standards-based server and
application consolidation
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Provides a data bridge between incompatible
technologies
Strong and use coupling
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Strong coupling occurs when a dependent class contains a
pointer directly to a concrete class which provides the required
behavior.
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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.
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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.
loose coupling
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Drawbacks of SOA
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SOA implementations are costly and time-consuming
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Requires complex security firewalls in place to
support communication between services
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Performance can be inconsistent
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Requires enterprise-level focus for implementation to
be successful
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
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ESOA supports reassembling smaller functionality
components and to develop new innovative business
solutions that meet ever changing business requirements.
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.
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Enterprise Service (ES)
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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)
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Enterprise services have the following Business
semantics:
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The model is based on process components, business
objects and global data types (GDTs)
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based on open standards. The interfaces are described
according to WSDL
SAP Enterprise Architecture framework
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Runtime Architecture Overview
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HTTP Communication Layer
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at SAP, all SOAP messages are sent via HTTP
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The main task of the layer is to accept incoming
HTTP requests and dispatch them to the
appropriate receiver.
Web Service Enabling Layer
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receives HTTP-based SOAP messages from the HTTP
Communication Layer
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It interprets the SOAP messages and extracts the
parameters for calling a Web service.
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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.
Web Service Enabling Layer
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Categories of web services
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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.
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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.
Synchronous Web Services
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Processes of Synchronous Service
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Dispatching a request (steps 1–3)
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Processing a request (steps 4–5)
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Sending a response (steps 6–8)
Dispatching a request
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The Internet Communication Manager (ICM) decides
whether to forward an incoming request to the ABAP
stack or the Java stack (base on URL part)
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The Internet Communication Framework (ICF)
receives all HTTP requests which are sent to the
ABAP stack and forwards the request to the
appropriate application.
Processing a request
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Reads the information in the SOAP header and extracts
the Web service data from the body of the message.
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The extracted XML Web service data is forwarded to the
proxy framework.
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The proxy framework maps the data from XML to ABAP
data structures and invokes the appropriate Web service
proxy.
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local calls