1. DSS & Warehousing Systems
Chapter 5
Efrem Mallach
Prepared by
Luvai Motiwalla
Irwin/McGraw-Hill
Copyright © 2000 by The McGraw-Hill Companies, Inc. All rights reserved.

2. DSS Architecture ,Hardware, And Operating Systems Platforms
Introduction
The elements of DSS architecture
The major options
DSS on the central corporate system
DSS and client /server computing
The internet and client/server computing in DSS
DSS using shared data on a separate system
DSS on a stand alone system
Open systems and DSS
Choosing a DSS hardware environment

3. Introduction
What is an information system architecture , and what are its benefits?
The difference between DSS architecture and overall corporate information systems architecture.
Pages 163 to 167
The architecture of an information system refers to the way its pieces are laid out, what types of tasks are allocated to each piece, how the pieces interact with each other, and how they interact with the outside world. The intent of an information system architecture whether for DSS or any other information system is to achieve the following:1) interoperability of systems, so that information can be brought to the point of use quickly and easily.2) Compatibility of systems, so that resources can be shared easily and leveraged across the organization. 3) Expandability of systems, so that limited single –function components do not create bottlenecks that obstruct the growth of the organization.
Having a well defined and well communicated decision support system architecture provides an organization with significant benefits. Non technical benefits include the ability to create a common vision that keeps all project participants working in tandem, the ability to communicate system concepts to management, the ability to communicate needs to potential vendors and the ability of other groups to implement systems that must work with the DSS. Technical benefits of a DSS architecture include the ability to plan systems in an effective and coordinated fashion and to evaluate technology options within a context of how they will work rather than abstractly.

4. The Elements of DSS Architecture
The eight elements a DSS architecture must represent:
Page 166
The eight elements a DSS architecture must represent:
Its database, its models, its users,
software tools for users, software tools for
administrators,hardware operating system
platforms,networking and communication
capabilities, the culture of an organization.
Its database or databases, including any existing data bases, internal or external to the organization,and any databases that are created specifically for DSS use.
Its model or models, including information about their sources of data, the organizational responsibility for maintaining them and limits on access on them.
Its users including any assumptions about their locations, jobs,levels of education, and any other factor that may affect their use of the DSS.
Software tools through which the users access the database and the models.
Software tools through which system administrators manage the database and the models.
Hardware and operating system platforms, at a generic level, on which the data base and models reside, on which the programs run, and through which users access the DSS.
Networking and communication capabilities through which these platforms are interconnected. These must reflect individual needs to connect to one or more servers and databases.
The culture of an organization that will use the DSS. If its culture is centralized, it may be acceptable to have a central database.

5. The Major Options There are major DSS platforms/ hardware environments
Page 168
The major DSS platforms/ hardware environments are:
1 The central corporate system
2 The central system linked to other computers on users desktops via a network.
3 A separate system that obtains data from the central system and provides it to users.
4 A freestanding system at the users desk.
5 A combination of the above.

6. DSS on the Central Corporate System
Corporate applications are generally put on the central system.
Pages 170 to 171
When corporate applications are generally put on the central system, and if this mode of regular load increases a new DSS can be put up. Doing so has both advantages and disadvantages.
Advantages:MIS staff members are already familiar with the system. Many users already know how the system works. The necessary hardware to use the system is already in place in the organization. DSS applications can access the central database directly for up to date information.The processing power of a large system can run complex DSS, such as large simulation models.Most large systems have a variety of available DSS tools.
Disadvantages: The central system was probably not originally selected for DSS applications and may not be well suited to them. The cost of additional resources to run a DSS may exceed the cost of smaller computers to handle the same task. There may be a tendency to force unsuitable software tools into DSS use, rather than getting suitable ones, because they are already there. DSS responsiveness may be impacted by other loads on the systems. DSS users may have to wait in line behind other application development efforts. The user interface of most large systems is not as easy for non technical people to use as that of most smaller systems. Support for graphics may be poor, even if an application can handle graphics.

7. DSS and Client/server Computing-cont’d
The approach of client/ server computing
Pages 171 to 174
The approach of client/ server computing allows a shared computer to provide decision support data and handle other aspects of the tasks to which it is well suited, while allowing more economical desk top computers to provide the user interface, while the server does the rest of the job.

8. DSS and Client/server Computing
Define:
1) Fat client
2) Thin client
3) Network computers
4) Intranet
Page 174
Fat client: client /server approaches where the client does most of the work, relying on the server only to supply it withdraw data, are often referred to as fat client approaches.
Thin client: A client system that does little more than provide a user interface to results provided by the server is often called thin client.
Network computers: is a desk top system that can access the web but has no stand alone computing capability.
Intranet: An intranet is an internal network that uses web protocols to control data transfer.

9. The Internet and Client/ Server Computing in DSS
The world wide web can also be used to supply decision support data to users
It has its disadvantages
Pages
Web access can be slow especially over standard modems and telephone lines
Web site designs and DSS designs are separate skills. Both are required for an effective web based DSS. Serving a given number of users with a web based or web like application requires a more pwerful server.

10. DSS Using Shared Data on a Separate System
Define a data warehouse
The advantages and disadvantages of using a data warehouse (or other separate DSS database)
Pages180 to 182
A data warehouse is a read only database. Its users cannot update the “live” or organizational information. That limits the use of data warehouse to situations where decision makers access corporate information but do not change it. If an application running in this environment must update the main database, it must be done in some other way. One approach is to have DSS computer mimic a transaction processing user and submit transactions.
Advantages: The DSS hardware can be optimized for the specific purpose. DSS hardware need not be shared with other applications. The cost of upgrading the central corporate system to run DSS applications is avoided. Compared to full blown client/server computing, in which the applications can update the server database, the unidirectional data warehouse environment is simpler and less prone to errors. Most servers and micro computers are user friendly or can be made so by an available graphical user interface package.
Disadvantages: the need to transfer data between two systems, to create the data warehouse and keep it up to date. The MIS staff must be familiar with two systems.users who access both systems may need two types of terminals. Decision support data are only as current as the most recent down load to data warehouse. Re creating the data warehouse may take several hours, and the DSS system may not be available for use during this time.

11. DSS on a Stand - Alone System
Many DSS that do not access a large central database are candidates for stand alone systems
Advantages and disadvantages of a stand - alone system
Pages 182 to 183
Advantages: The system can be totally optimized for DSS. The complexity of sharing a resource with other users is avoided.The complexity of integrating a two system application is avoided. There is no overhead in communicating with other systems. The person or department owning the system has complete control over it.
Disadvantages: Any data the system requires must be provided by its user. Sharing the results with other users, or using a shared database, may be more difficult that it would be if the system were designed to operate in a shared – data environment.The individual user or department responsible for the stand – alone system must usually deal with its own system administration needs. It may be difficult to integrate a stand – alone system with corporate applications at a later date if no thought was given to compatibility in the planning stages.

12. Open Systems and DSS What is an Open system? Aspects of openness
DSS has accelerated the growth of open systems
Pages 184 to 188
Open systems are systems whose interfaces are not under the control of any single hardware or software supplier. Rather they are defined by neutral bodies through an open process in which all parties can, if they choose , participate. Once they are agreed upon, both the interface specifications and the right to produce systems that conform to those specifications are available on equal, and equitable terms to all firms.
System openness encompasses multiple aspects. The first aspect is system interconnection, or networking. The second aspect of openness is the way individual computers operate. The multi user open operating systems are UNIX, POSIX, and at the desk top level, Microsoft windows. The third aspect of openness is hardware interface openness. Hardware interfaces to many microcomputers and minicomputers are in the public domain or can be licensed.
DSS has accelerated the growth of open systems. The reason: the arrival of DSS injected a second component into what had been, historically, single purpose transaction processing systems.

13. Choosing a DSS Hardware Environment
Questions to be asked before choosing a right DSS hardware approach.
Page 189
Are there any corporate policies that you must follow?
How large and widespread will the DSS user community be?
Are most of the prospective users already using a particular system?
Is there any corporate mainframe with sufficient capacity?
Is another powerful server system available?
Do prospective users already have microcomputers or work stations that can handle the application?
If new system are required, will the existing central system be able to share data with them?
Do the necessary development tools, if any, are the prospective DSS developers already familiar?
Does the application require access to a database?
Does the application’s use off the corporate database require only the ability to read the data, or must it also be able update the data?
How much processing power does the application require?
Are prospective users capable of performing basic system administration tasks, such as installing software and backing up data files?