Chapter 3 E-commerce ArchitectureChapter - 3 E-commerce Architecture 26 Chapter 3 E-commerce Architecture 3.1. E-commerce Architecture: Every day more and more business transactions are conducted in the Internet under the umbrella of ECommerce. The main feature that distinguishes E-Commerce from traditional commerce is the ability to conduct business with spatially distributed partners and products, and achieves considerable reduction in human effort and latency time. The size and complexity of E-Commerce systems make the architecture level of design and specification of the overall system a significant issue. From a good design it is possible to assess the quality and performance of the system before the system is implemented and deployed. Some of the important properties that can be assessed from a design specification include correctness, service availability, and security of transactions. This paper discusses the model of E-Commerce architecture towards this goal. There are four types of E-commerce Architecture 1. Client Server Architecture 2. Two-Tier Architectures 3. Three-Tier Architectures 4. Distributed Enterprise Architecture 3.2. Client–server architecture: The client–server architecture is a computing model that acts as a distributed application which partitions tasks or workloads between the providers of a resource or service, called servers, and service requesters, called clients. [Fig: Client Server architecture] 27 Network traffic (network servers). A client does not share any of its resources. the computer that sends the HTML files is the server 4. Process requests from clients. Example: E-mail client an application that enables you to send and receive e-mail. • In e-commerce the client is defined as the requestor of a service and a server is the provider of the service 3. Uses client/server model and http(hypertext transfer protocol) 28 . Clients (Clients are Applications): Applications that run on computers and Rely on servers for Files. Client processes requesting service from server processes 2. interoperability and scalability. Clients therefore initiate communication sessions with servers which await incoming requests. Make requests. Devices.Store and protect data. 5. Communication Networks: Networks Connect Clients and Servers. First used in 1980s. A server machine is a host that is running one or more server programs which share their resources with clients. but both client and server may reside in the same system. Disk drives (file servers). Processing power. Client Server architecture use 3 components1. but requests a server's content or service function. Example: Database Server -A computer system that processes database queries. Browser is the client and the customer.2. 3. Servers (Servers Manage Resources): Computers or processes that manage network resources. 2. The server can also be a computer program that provides services to other computer programs • A web server is the computer program that serves requested HTML pages or files. Format data on the desktop. the model improves to be e-commerce usability.Chapter 3 E-commerce Architecture Often clients and servers communicate over a computer network on separate hardware. A network architecture in which each computer or process on the network is either a client or a server. flexibility. 3. Client/Server architecture Propertis: E-commerce is based on client/ server architecture 1. Printers (print servers).1. The server component provides a function or service to one or many clients. The client–server model has become one of the central ideas of network computing. which in turn serves it back to the web browser client displaying the results to the user. Clients-server interaction: The client–server characteristic describes the relationship of cooperating programs in an application. web access and database access. Many 29 . Users accessing banking services from their computer use a web browser client to send a request to a web server at a bank. That program may in turn forward the request to its own database client program that sends a request to a database server at another bank computer to retrieve the account information. Functions such as email exchange. downloading requests for FTP files and building and publishing web pages. In client/ server architectures client and server typically communicate through statements made in structured query language (SQL). The balance is returned to the bank database client. which initiate requests for such services. The client/ server model improves multi-user updating through a graphical user interface (GUI) front end to the shared database. • • • • • • Typically the e-commerce customer is the client and the business is the server. 3.2. • • Most popular web servers are Deerfield’s WebSite and Microsoft’s Internet Information Server (IIS) Web servers are included as part of a larger package of internet and intranet related programs for serving e-mail.Chapter 3 E-commerce Architecture 6. In the client/ server model single machine can be both client and the server The client/ server model utilises a database server in which RDBMS user queries can be answered directly by the server The client/ server architecture reduces network traffic by providing a query response to the user rather than transferring total files. Every computer on the internet that contains a web site must have a web server program. are built on the client–server model.2. application servers.The interaction between client and server is often described using sequence diagrams. print servers. Most web services are also types of servers.2. Client/Server with File Servers In the client/server architecture. file servers. 3.3. The Unified Modeling Language has support for sequence diagrams.Chapter 3 E-commerce Architecture business applications being written today use the client–server model. and terminal servers. FTP servers. Any computer can be configured to be a host and act as a file server. email clients. Telnet. So do the Internet's main application protocols. Specific types of servers include web servers. a file server is a computer responsible for the central storage and management of data files so that other computers on the same network can access the files. and online chat clients. name servers. and DNS. SMTP. [Fig: Centralized Client/Server with File Servers] 30 . A file server allows users to share information over a network without having to physically transfer files by floppy diskette or some other external storage device. Specific types of clients include web browsers. database servers. mail servers. such as HTTP. database master servers are central and primary locations of data while database slave servers are synchronized backups of the 31 . Database management systems frequently provide database server functionality. 3. allowing anyone on the network to store files on it as if to their own hard drive. [Fig: Distributed Client/Server with File Servers ] A program or mechanism that enables the required processes for file sharing can also be called a file server. such programs often use the File Transfer Protocol (FTP). Client/Server with Database Servers : A database server is a computer program that provides database services to other computer programs or computers. as defined by the client–server model. The term may also refer to a computer dedicated to running such a program. On the Internet.4. Such a server is accessed either through a "front end" running on the user’s computer which displays requested data or the "back end" which runs on the server and handles tasks such as data analysis and storage.. a file server might be a dedicated network attached storage (NAS) device that also serves as a remote hard disk drive for other computers. In a master-slave model.Chapter 3 E-commerce Architecture A file server may be an ordinary PC that handles requests for files and sends them over the network. In a more sophisticated network.2. MySQL) relies exclusively on the client–server model for database access. and some DBMS s (e.g. Chapter 3 E-commerce Architecture master acting as proxies. Richard Finkelstein. temporal conditions. Client/Server with Transaction Processing : 32 . Performance Computing 3. DB2. SQL Server. Every server uses its own query logic and structure. [Fig: Client/Server with Database Servers ] A DBMS also offers features for recovery and concurrency control Some examples of Database servers are Oracle.2. The SQL query language is more or less the same in all the database servers. blackboards. Ingres. Informix. and event.5. errors) trigger event handlers-> implicit invocation. and it is here that the greatest challenge to any corporation currently lies. President. At present the majority of existing client/server-based software is to be found in the area of databases. Events (violation of integrity constraints. displays on the clients’ screens.salaray > salary c) Isolation [Fig: Client/Server with Transaction Processing ] d) A transaction’s behavior not affected by other transactions running concurrently . salary increase for all 1 million employees or none 2) Consistency a) a transaction is an indivisible unit of work b) integrity constraints (e. c) All updates to a database. consistent state. b) An all-or-nothing proposition .g. 1) Atomicity a) A transaction is an indivisible unit of work. d) e. by ensuring that any operations carried out on the system that are interdependent are either all completed successfully or all canceled successfully. 33 .g.Chapter 3 E-commerce Architecture Transaction processing is designed to maintain a computer system (typically a database or some modern file systems) in a known. message queues.. mgr.. virtual private network (VPN). 3) Serialization techniques a) Durability b) Persistence c) A transaction’s effects are permanent after it commits 3. on each computer that they use. Centralized Server Advantage Having a single server hosting the database of user names and passwords and. Advantages of Client Server Architecture : 1) Centralization: In Client Server Networks there is no central administration. Access rights and resource allocation is done by Servers.g. reserve a seat. In this way. as resource access and log-on permissions would have to be configured for each user. server can be accessed remotely. in case of some break-down if data is lost. Servers that allow remote access offer different type of secure connection like wireless. managing what levels of access individual users and computers can have to specific network resources is a distinct advantage of client server architecture. This advantage is even greater in networks where users typically access resources from a number of computers. at the same time. Also it becomes easier to find files. Also new resources and systems can be added by making necessary changes in server. Accessible client server system can be set up with a remote access. While maintaining the security 34 . Computers and servers to a client server network without major interruptions to the network Changes can be made easily by just upgrading the server. or dial-up remote access. 3) Back-up and Recovery possible: As all the data is stored on server its easy to make a back-up of it. 5) Accessibility: From various platforms in the network. Fewer support staff are needed to manage centralized security accounts than would be needed if security and resource access had to be configured on each individual computer on the network. While in peer computing we have to take backup at every workstation. It means users can access the network securely from the outside.2. Servers help in administering the whole set-up. Also. 4) Up gradation and Scalability in Client-server set-up: A client server system allows the network to easily adapt to upgrades and new technologies. 2) Proper Management: All the files are stored at the same place. it can be recovered easily and efficiently. management of files becomes easy. A new operating system or a software upgrade can be implemented from the server across the network without much downtime or inconvenience to users. here in this architecture there is a centralized control.6.Chapter 3 E-commerce Architecture e) E.. All the changes are made only in central computer on which server database exists. as the failure of a single computer does not prevent users of other computers from logging on and accessing network resources. However. whether a quick access to check emails or a work from home privilege. 35 . the whole network goes down. 2. Congestion in Network: Too many requests from the clients may lead to congestion. A network where log-on information is configured and held on each computer does not have this problem. limiting the number of people with access to them and increasing security features of the servers. 3. If the centralized server is removed from the system or goes down due to problems. they would have provided the broken parts of file. download stops altogether. there is always the chance that a failure of the server will bring network business to a halt. Overload can lead to breaking-down of servers. Disadvantages of Client Server Architecture: 1. Client-Server architecture is not as robust as a P2P and if the server fails. Only the failed computer is affected. if you are downloading a file from server and it gets abandoned due to some error. if there would have been peers. However.2. 6) As new information is uploaded in database. Also. the entire network cannot function.7. 8) Servers can play different roles for different clients. each workstation need not have its own storage capacities increased (as may be the case in peer-to-peer systems). many client server networks now have backup servers to provide support when a server is lost. 7) Security: Rules defining security and access rights can be defined at the time of set-up of server. For example. Client-server arrangements aid security efforts because there are fewer servers. which rarely takes place in P2P network. and the server suffers a failure. Dependence: The client-server network model relies on a functioning and available centralized server. if a single server hosts the user names and passwords database for a network. Wherever a single server is used to manage resources on a network. a client server system provides the users the comfort and convenience of accessing the network from the outside. 3.Chapter 3 E-commerce Architecture of the network. no users will be able to log on to the network until the server is fixed or replaced. A client/server network can be expensive to implement and maintain. which can be both an advantage and a disadvantage. data stored remotely can be more secure than data stored locally. but additional training is often required as a result. Other network operating systems. a backup system is needed. a server operating system and appropriate licenses to allow the end users to use the network software. IT security professionals. For instance. Downtime: When a computer in a simple peer-to-peer network goes down. manage security and backup systems. at least one server is required to create a client/server network. but more configurations is required both to ensure the security of that data and to allow the appropriate users to have appropriate access to that data. Typically. If security is maintained centrally on that server. Depending on the size and complexity of the client/server network. as this work is distributed among individual clients and their related machines. and/or other IT professionals. the central server computer must be powerful enough to maintain and share resources with the other computers on the network. This requires server hardware and software. which translates into an additional salary. Personnel a client/server network requires experienced network personnel to maintain the server. and perhaps any users who are trying to access data stored on that computer. You need professional IT people to maintain the servers and other technical details of network. For a smaller network. the only users affected are the user of that particular computer. workstations are unable to authenticate login 36 . First. Complexity: A client/server network is naturally more complex. Cost: It is very expensive to install and manage this type of computing. do not require a network administrator to maintain machines. 5. This entails a substantial cost. If data will be stored centrally. when a server in a client/server network goes down. A smaller network may be able to combine several of these roles into one position. cost alone may be the deciding factor in opting for a different type of network architecture. this could require network administrators. Maintaining a client/server network also requires at least one network administrator. In contrast. which requires backup server software and backup media. 6. 7.Chapter 3 E-commerce Architecture 4. Maintenance Client-server networks often requires a staff with at least a single network administrator to manage and maintain the equipment and the network. and recover quickly from unexpected outages. 8. The very nature of a client/server environment creates challenges in the delivery and accessibility of remote resource. all users are affected. such as peer-to-peer network systems. As a result. two-tier applications do not scale as easily as other architectures. and users are unable to gain access to their own systems. it is also the most restrictive. Two-tier Considerations: • Requires a code change to port to a different database Potential bottleneck for data requests 37 . The database session provides TopLink support for two-tier applications.Chapter 3 E-commerce Architecture information.3. the two-tier model is not as common as the three-tier model. Two-Tier Architectures: A two-tier application generally includes a Java client that connects directly to the database through TopLink. The two-tier architecture is most common in complex user interfaces with limited deployment.3. Two-tier applications are often implemented as user interfaces that directly access the database They can also be non-interface processing engines. If user data is stored centrally. If applications are managed centrally. because each client application requires its own session. Any of these scenarios can result in significant loss of productivity and/or revenue. 3. users are unable to run their applications. Client User Interface (Business Rules) Server (Business Rules) Data Access [Fig: Two Tier Client Server] Two-tier architectures have 2 essential components • • A Client PC and A Database Server Client program accesses database directly o o 3. Although the two-tier architecture is the simplest TopLink application pattern.1. In either case. users are unable to access their data. • The user system interface is usually located in the user’s desktop environment and the DBM services are usually in a server that is a more powerful machine that services many clients. CPU) o Requires application code to be distributed to each client workstation . usually on a different computer: 38 .Chapter 3 E-commerce Architecture o • High volume of traffic due to data shipping Limited by processing capability of client workstation Client program executes application logic o (memory. [Fig: Two Tier Architecture] • It runs the client processes separately from the server processes. 2. which provides higher performance. Performance: Adequate performance for low to medium volume environments Business logic and database are physically close. Internet retrieval. • Also lacks flexibility in moving program functionality from one server to another. and static business rules. homogeneous applications.Chapter 3 E-commerce Architecture 1. 3.3. The advantages of the two tier architecture : • Development Issues: Fast application development time. Implementation of processing management services using vendor proprietary db procedures restricts flexibility and choice of RDBMS for applications. 1. monitors security and permissions. desicion support Used in distributed computing when there are fewer than 100 people simultaneously interacting on a LAN.3. Fundamental units of work required to complete the business process 2. • 3. Business rules can be automated by an application program • • • Typically used in e-commerce 1. The disadvantages of the 2-tier architecture : 39 . Conducive to environments with homogeneous clients. Easy to setup and maintain available tools are robust and lend themselves to fast prototyping to insure user needs a met accurately and completely. The server processes provide an interface with the data store of the business. This part of the application is the presentation layer 2. and gather and present data usually on the customer’s computer. The client processes provide an interface for the customer.3. The business logic that validates data. This part of the application is the data layer 3. or split between the two. and performs other business rules can be housed on either the client or the server. Performance: Inadequate performance for medium to high volume environments. When logic is in the client. the database performance degrades. When there are a large number of users. Poor Logic Sharing: Traditional two-tier architectures keep business logic on the client. The chief reason is that each client requires its own connection and each connection requires CPU and memory. This is true even for large database servers. This means that it is more difficult to redesign the database since other applications are intimate with the actual database structure. Development Issues: Complex application rules difficult to implement in database server – requires more code for the client. Application Distribution: Application changes have to be distributed to each client. this entails considerable administrative overhead. Changes to business logic not automatically enforced by a server – changes require new client side software to be distributed and installed. since database server is required to perform business logic. Database Structure: other applications that access your database will become dependent on the existing database structure. As the number of connections increases. Application performance can be expected to degrade rapidly when the number of concurrent users reaches a threshold between a few hundred and one thousand users. Not portable to other database server platforms. Remote Usage: Remote users (e. This slows down database operations on database server. probably do not want to install your application on their clients-they would prefer "thin" clients where minimal (or no) client software installation is required. • • • • • • 40 .Chapter 3 E-commerce Architecture • Scalability: key concern with the 2-tier model is scalability. Complex application rules difficult to implement in client and have poor performance.g. customers). it is usually more difficult to re-use logic between applications and amongst tools. [Fig: Three Tier Architecture] The most widespread use of multi-tier architecture is the three-tier architecture. computer data storage and data access are developed and maintained as independent modules. and the data management are logically separate processes. It was developed by John J. For example. Three-Tier Architecture( Multitier architecture ): Multi-tier architecture (often referred to as n-tier architecture) is a client– server architecture in which the presentation.Chapter 3 E-commerce Architecture 3. an application that uses middleware to service data requests between a user and a database employs multi-tier architecture. Three-tier is a client–server architecture in which the user interface. Donovan in Open Environment 41 . most often on separate platforms. functional process logic ("business rules").4. the application processing. tier 2 (business objects. There should be a presentation tier. The three-tier model is software architecture and a pattern. Three-tier (layer) is a client-server architecture in which the user interface. while a tier is a physical structuring mechanism for the system infrastructure. The concepts of layer and tier are often used interchangeably.4. 3. the three-tier architecture is intended to allow any of the three tiers to be upgraded or replaced independently in response to changes in requirements or technology.Chapter 3 E-commerce Architecture Corporation (OEC). rather than have to rewrite the entire application over. and 42 .1. Basically. Typically. business process (business rules) and data storage and data access are developed and maintained as independent modules or most often on separate platforms. developers only have to modify or add a specific layer. and an RDBMS on a database server or mainframe contains the computer data storage logic. • Presentation tier Or Presentation Layer (UI):This is the topmost level of the application. However. a change of operating system in the presentation tier would only affect the user interface code. The presentation tier displays information related to such services as browsing merchandise. Three-tier of the architecture: N-tier application architecture provides a model for developers to create a flexible and reusable application. The middle tier may be multi-tiered itself (in which case the overall architecture is called an "n-tier architecture"). and a data tier. one fairly common point of view is that there is indeed a difference. a business or data access tier. For example. purchasing. there are 3 layers : Tier 1 (presentation tier. a tools company he founded in Massachusetts. Apart from the usual advantages of modular software with well-defined interfaces. By breaking up an application into tiers. and that a layer is a logical structuring mechanism for the elements that make up the software solution. functional process logic may consist of one or more separate modules running on a workstation or application server. GUI tier). business logic tier) and tier 3 (data access tier). the user interface runs on a desktop PC or workstation and uses a standard graphical user interface. ) • 3.A computer hosting a database management system (DBMS). or middle tier): The logic tier is pulled out from the presentation tier and. Giving data its own tier also improves scalability and performance.Chapter 3 E-commerce Architecture shopping cart contents. A Server computer that hosts components which encapsulate an organization's business rules.aspx or windows form where data is presented to the user or input is taken from the user. logic tier. BAL contains business logic. Middle-tier components can either be Active Server Page scripts executed on Internet Information Server. or (in non-Webbased applications) compiled executables.4. might be returning data or manipulating data (insert. Presentation layer contains pages like . (In a two-tier application. data access tier. it controls an application’s functionality by performing detailed processing. update. I will call it Business Access Layer in my demo. or (in non-Web-based applications) a stand-alone compiled front-end application • Application tier ( business logic. validations or calculations related with the data.DAL contains methods that helps business layer to connect the data and perform required action. delete etc). This tier keeps data neutral and independent from application servers or business logic. It communicates with other tiers by outputting results to the browser/client tier and all other tiers in the network.2. if needed. Component & Consideration of 3tier architecture: Three Tier architectures have 3 essential components: • • • A Client PC An Application Server A Database Server Three-Tier Architecture Considerations: 43 . Data Access Layer (DAL) Or Data tier: This tier consists of database servers. as its own layer. the middle-tier and data source tier are combined. A local computer on which either a Web browser displays a Web page that can display and manipulate data from a remote data source. such as a Microsoft SQL Server database. Here information is stored and retrieved. 3. Transaction processing (TP) monitors 44 .4.3.A middle tier is added between the client environment and the DBM server environment. Implemantation of 3 Tier Architecture: Variety of ways to implement three tier architectures : 1.Chapter 3 E-commerce Architecture • Client program contains presentation logic only o o o Less resources needed for client workstation No client modification if database location changes Less code to distribute to client workstations • One server handles many client requests o o More resources available for server program Reduces data traffic on the network [Fig: 3 Tier Architecture] Also called as multi-tier architecture. Three-Tier Architectures with Message Server : • Messages are prioritised and processed asynchronously 45 .4.4.2.Chapter 3 E-commerce Architecture 2.Three-Tier Architectures with TP Monitor : • The most basic type o Type of message prioritisation service queuing. Application servers 3. • • Client connects to TP instead of the DB server The transaction is accepted by the monitor which queues it and takes responsibility to complete it by freeing up the client When a third part provides this service it is called TP heavy When it is embeded in the DBMS.3. Message servers 3.1. transaction scheduling. it can be considered 2-tier and is referred to as TP lite TP monitor provides: o o • • • The ability to update multiple DBMSs in a single transaction Connctivity to a variety of data sources (flat files & nonRDBMSs) The ability to attach priorities to transactions Robust security o o • • More scalable than a 2-tier architecture Most suitable for e-commerce with many thousands of users 3.3. The application server does not drive GUIs rather it shares business logic. With less sw on the client 1. Support and installation costs are less on a single server than maintaining each on a desktop client.4. 3. 3.4. computations.3. There is less concern with security. Applications are more scalable 3. whereas the TP environment has the intelligence in the monitor and treats transactions as dumb data packets They are sound business solutions for the wireless infrastructures of m-commerce. Three-Tier Architectures with an Object Request Broker Standard: 46 . Three-Tier Architectures with an Application Server : 1. the address.3. • 3. and a data retrieval engine.3.4. 2.Chapter 3 E-commerce Architecture 1. the id no • • Message server connects to the RDBMS and other data sources The message server focuses on intelligent messages. Headers contain priority info. Allocates the main body of an application to run on a shared host rather than in the user system interface client environment 2. b. will need only some changes in the components of the presentation layer. ORB support in a network of clients and servers on different computers means o • A client program (object) can request services from a server program Object without having to understand where the server is in a distributed network or what the interface to the server program looks like o • ORB is the programming that acts as the mediary or as a broker between a client request for a service from a distributed object or component and server completion of that request. There are two prominent distributed object technologies: o o • Common Object Request Broker Architecture (CORBA) Component Object Model (COM) • The industry is working on operability between CORBA and COM 3. For example: A change from one DBMS to other will only involve a change to the part in the data access layer.4. CSS and XLS skills for presentation layers. A change in the Use Interface (from desktop to the web. The benefit of writing the presentation and business layered architecture in different languages is that it is an advantage of the presentation and business layers is that it is feasible to use different developer teams to work on each. Advantages of 3 tier architecture : a. It is easier to find a 47 . The advantage of a 3-tier system is that the contents of any of the tiers/layers can be replaced without making any resultant changes in any of the others. and HTML.Chapter 3 E-commerce Architecture • Need for improving interoperability and object request broker (ORB) standards in the client/ server model.4. It means that only PHP skills are required for data access layer and business layer. g. Another main advantage of using XML/XLS in the presentation layer is that it the output can be changed from HTML to WML or PDF or any other format using a different XLS style sheet. c. i. In addition. XLS files can be used to change XML documents into a number of formats and not only HTML. It has better wait balancing system because the entire work load is divided. TP monitors or ORBs can be used to balance loads and dynamically manage the number of application server(s) available. e. Scalability: The key 3-tier benefit is improved scalability since the application servers can be deployed on many machines. j. Business logic is generally more secure since it is placed on a more secure central server. the middle tier can ensure that only valid data is allowed to be updated in the database and the risk of a rogue client application corrupting data is removed. then the specific language implementation of the middle tier can be made transparent.it only requires connections from a smaller number of application servers. h. the database no longer requires a connection from every client -. Also. Improved Security: Security is improved since it can be implemented at multiple levels (not just the database). Improved Data Integrity: since all updates go through the middle tier. If an object standard like COM/DCOM or CORBA is employed (as discussed in tool dependence). d.Chapter 3 E-commerce Architecture developer with skills in one of these rather having a kind of developer having all of the skills. f. Better Re-use: The same logic can be initiated from many clients or applications. 48 . Since the client does not have direct access to the database. Security polices can be imposed without effecting the clients. Security can be granted on a service-by-service basis. Reduced Distribution: Changes to business logic only need to be updated on the application servers and do not have to be distributed to all the clients. it is more difficult for a client to obtain unauthorized data. It is likely that additional programming effort will be required to manage tasks that an automated tool might handle in a 2-tier environment. Business logic off-loaded from database server and client. which improves performance. Application server logic is portable to other database server platforms by virtue of the application software . it is possible to architect an application so that it can recover from network or server failures.Chapter 3 E-commerce Architecture k. The disadvantage of the 3-tier architecture : a. Development Issues: Complex application rules easy to implement in application server.g. PowerBuilder.4. The points of communication are doubled (client to middle tier to server. Improved Availability: mission-critical applications can make use of redundant application servers and redundant database servers. server load balancing. most reporting tools). Therefore. m. Hidden Database Structure: since the actual structure of the database is hidden from the caller. it is possible that many database changes can be made transparently. l.5. n. b. Current tools are relatively immature and are more complex. Creates an increased need for network traffic management. Performance: Superior performance for medium to high volume environments 3. it is more difficult to build a 3-tier application compared to a 2-tier application.g. With redundant servers. instead of simply client to server) and many handy productivity enhancements provided by client tools (e. This is a potential obstacle for simplifying maintenance and promoting code reuse 49 . Visual Basic. Delphi) will be foregone or their benefit will be reduced with a 3-tier architecture. Maintenance tools are currently inadequate for maintaining server libraries. a service in the middle tier that exchanges information/data with other applications could retain its original interface while the underlying database structure was enhanced during a new application release. and fault tolerance. Fewer Tools: There are many more tools available for a 2-tier model (e. Increased Complexity/Effort: In general. Changes to business logic automatically enforced by server – changes require only new application server software to be installed. Chapter 3 E-commerce Architecture throughout the organization. Distributed Enterprise Architecture : 50 . Development Issues: For More complex structure it is more difficult to setup and maintain. c. There is more processing on the web server. 3. e. Performance: The physical separation of application servers containing business logic functions and database servers containing databases may moderately affect performance.5. It does not interact with the WMS server directly. d. More complex structure more difficult to setup and maintain the physical separation of application servers containing business logic functions and database servers containing databases may moderately affect performance. the Data Adapters can be and in fact were distributed to other machines to support the Distributed Enterprise Architecture effort on IL’03. The notion here is that it is easy to use different devices on the network to do data collection so that a) we can avoid overloading any given device and b) we can place bandwidth intensive Data Adapters on the same LAN (and even the same virtual LAN) as other important devices to minimize ill effects of highly distributed systems. [Fig: Logical diagram of an Enterprise Architecture] The design has further been guided by the need for the Data Collection component to be real-time and for the analysis component to at least be 51 .Chapter 3 E-commerce Architecture The Distributed Enterprise Architecture has been designed to support distribution of key components. For instance. refresh. Because the system is web-based. run interactive queries against Distributed Enterprise Architecture databases and view. or publish analysis products. anyone anywhere on the network (connected via WAN or LAN and possessing the appropriate privileges) can log onto the Distributed Enterprise Architecture Portal (described below). 5. and system parameters are stored in name-value pairs. 3. a complete Distributed Enterprise Architecture system can be run on a single highend laptop. Distributed Enterprise Architecture with the emergence and popularity of ERP sw. As the load placed on the Distributed Enterprise Architecture system increases. Basic Properties of Distributed Enterprise Architecture : Distributed Enterprise Architecture collection parameters are typically specified in collection strategies. from configuration.Chapter 3 E-commerce Architecture near real-time. either through the expansion of the collection requirements or through increased user traffic supported by the Distributed Enterprise Architecture Portal. separating the data layer from the integration/services layer) allow the analysis component to be able to yield limited results in real time or more complete results at near real time or after action. • • 52 .g. Distributed Enterprise Architecture uses shared. distributed enterprise architecture promises to enable e-commerce to extend business processes at the enterprise level. • • Distributed Enterprise Architecture based on ORB technology . additional servers are needed to distribute the load so that the Data Adaptors do not fall behind and the Portal remains responsive A guiding principle in the design of the Distributed Enterprise Architecture system is to separate functionality. Implemented by code. The Data Adapter framework incorporates real-time control and exception management. reusable business models on a business enterprise-wide scale. The multiple layers (e.1. Distributed Enterprise Architecture is standardised business object models and distributed object computing are combined to give greater flexibility to the business . all of which is stored in a central database. Currently. Chapter 3 E-commerce Architecture [Fig: critical components of any distributed enterprise architecture] 3. Software implementation is difficult. More components to fail because of so many components are used. Allows significant modification of DCA deployment without code changes. 3. The Disadvantages of the Distributed Enterprise Architecture : 1. Non-developers can configure the DCA and the Data Adapters. Security issue is low to maintain. 4. 2. Network setup is complicated. 3.2.3.5. 3. The advantages of the Distributed Enterprise Architecture : 1. 53 . 2. Collection Strategies and system parameters can be configuration managed separately from the code base.5.