Ch2: Database Development within IS Development

Enterprise Data Modeling: The first step in database development, in which the scope and general content of organizational databases are specified.

Information systems architectures (ISA): A conceptual blueprint or plan that expresses the desired future structure for the information systems in an organization.

An ISA consists of six key components:

1. Data
2. Processes--that manipulate data
3. Network--which transports data around the organization and between organization and its key business partners
4. People--who perform processes and are the source and receiver of data and information
5. Events and points in time--when processes are performed
6. Reasons--for events and rules that govern the processing of data

Information Engineering: A formal top-down, data-oriented methodology that uses a data orientation to create and maintain information systems. Includes for steps: planning, analysis, design, and implementation.

Top-down planning: A generic IS planning methodology that attempts to gain a broad understanding of the information system needs of the entire organization.

Information Systems Planning

Identifying Strategic Planning Factors

1. Organizational goals (e.g. "maintain 10% per year growth rate")
2. Critical success factors (e.g. "high quality products")
3. Problem areas (e.g. "inaccurate sales forecasts")

Identifying Corporate Planning Objects

CPO define the business scope.

1. Organizational units--various departments
2. Organization locations
3. Business functions (A related group of business processes that support some aspect of the mission of an enterprise.)
4. Entity types--CUSTOMER, PRODUCT, ORDER, etc
5. Information systems--transaction processing systems (order tracking, order processing, payroll, etc.), management information systems (sales management, inventory control, etc.)

Developing an enterprise model consists of a functional breakdown (or decomposition) model of each business function, an enterprise model, and various planning matrices.

Functional decomposition: An iterative process of breaking down the description of a system into finer and finer detail in which one function is described in greater detail by a set of other, supporting functions.

An enterprise data model shows not only the entity types, but also the relationships between data entities.

A common format for showing the interrelationships between planning objects is matrices; several common matrices are:

• location-to-function: indicates what business functions are being performed at which location
• unit-to-function: identifies which business functions are performed by or are the responsibility of which business units
• IS-to-data entity: explains how each IS interacts with each data entity
• supporting function-to-data entity: identifies which data are captured, used, ... within each function
• IS-to-objective: shows which IS support which business objective

Further, matrices prove to be useful for:

1. identifying orphans
2. spot missing entries
3. prioritize development

DB Development Process and SDLC

SDLC: The traditional methodology used to develop, maintain, and replace information systems

Enterprise Modeling

• set the range and general content of organizational databases
• review current databases and information systems; analyze the nature of the business area that is the subject of the development project; describe, in general terms, the data needed for each IS under consideration for development

Conceptual Data Modeling

• analyze the overall data requirements of the proposed IS
• ...
• produce detailed data model, which identifies all the organizational data that must be managed by this IS
• define every data attribute, list all categories of data, represent every business relationship between data entities, specify every rules that dictates the integrity of data

Logical Database Design

• transform the conceptual data model into a standard notation called relations (based on relational DB theory)
• perform a detailed review of the transactions, reports, displays, and inquiries supported by the database
• verify exactly what data are to be maintained in the DB and the nature of those data as needed for each transaction, report, etc.
• transform the combined and reconciled data specifications into basic or atomic elements following well-established rules for well-structured data specifications
• begin to specify the logic of the particular computer programs and queries needed to maintain and report the database contents.

Physical Database Design and Definition

• decide ont he organization of the DB in storage (usually disk) and define the physical structure of the DBMS
• outline the program to process transactions and to generate anticipated management information and securely handle all data processing against it

Database Implementation

• write, test, and install programs that process the DB (in standard programming languages like COBOL, C or VB; or in special DB processing language like SQL; or special-purpose nonprocedural languages to produce stylized reports and displays)
• finalize all DB documentation, train users, and establish procedures for ongoing support of IS and DB users
• load data from existing information sources
• put DB and associated applications into production for data maintenance and retrieval by actual users

Alternative IS Development Approaches

Prototyping: An iterative rapid application development (RAD) method of systems development in which requirements are converted to a working system that is continually revised through close work between analysts and users.

The Role of CASE and a Repository

Computer-aided software engineering (CASE) tools: Software tools that provide automated support for some portions of the systems development processes.

3 relevant features of CASE tools:

1. the ability to help us draw data models using entity-relationship (ER) and other notations; a CASE tool's drawing capabilities are "database intelligent" in that each symbol represents specific data modeling constructs, and these symbols can be used only in ways consistent with the properties of the associated constructs.
2. the ability to generate code; often, this code contains the database definition commands to be given to a DBMS: case tools can refer to all data specifications and compose SQL commands to create relational tables, define each attribute of each table, and define the key indices
3. the ability to serve as an information repository

Information repository: a knowledge base of information about the facts that an enterprise must be able to access and the processes it must perform to be successful

Managing the People involved in DB Development

A systems or DB development team can include one or more of each of the following:

• Systems analysts
• Database analysts
• Users
• Programmers
• Database and data administrators
• Other technical experts (in networking, operating systems, testing, and documentation)

3-Schema Architecture for DB Development

Conceptual Schema

Conceptual Schema: A detailed, technology independent specification of the overall structure of a database or organizational data that is independent of amy DBMS technology.

• It defines the whole database without reference to how data are stored in a computer's secondary memory.
• It is usually depicted in a graphical format using entity relationship (E-R) or object modeling notations (we call this the data model)
• specifications for the CS are stored in as metadata in a repository or data dictionary

External Schema, or User View

• user view: logical description of some portion of the DB that is required by a user to perform some task
• also independent of DB technology
• contains a subset of the conceptual schema , relevant to a particular user or group of users
• the version of the conceptual schema used in a particular program

Physical or Internal Schema

Physical Schema: Specifications for how data from a conceptual schema are stored in a computer's secondary memory.

Three-Tiered DB Location Architecture

1. Client tier. A desktop or laptop computer, which concentrates on managing the user-system interface and localized data; also called the presentation tier. Web scripting tasks may be executed in this tier
2. Application/Web server tier. Processes HTTP protocol, scripting tasks, performs calculations, and provides access to data; also called the process services tier.
3. Enterprise server (minicomputer and mainframe) tier. Performs sophisticated calculations and manages the merging of data from multiple the merging of data from multiple sources across the organization; also called the data services tier.

Client/Server Architecture: A local area network-based environment in which database software on a server (called a database server or database engine) performs database commands sent to it from client workstations [in order for] application programs on each client [to] concentrate on user interface functions.

Using the Access (DBMS)

MS Access provides capabilities to develop several types of pre-written routines that can make it easier for Helen to answer standard (known) questions, so that the user does not have to program there questions from scratch:

• Form. A set of attributes, in a predetermined format, all based on a single database record.
• Report. A set of attributes, in a predetermined format, based on many unrelated records. A report usually contains the same attributes about each record.
• Query. A question to be answered from the database as posed in a particular querying language, Query-by-Example. The result of a query is a table in which the columns are the attributes the user wants to see and the rows are different instances of those attributes that satisfy the qualification entered by the user.