Database Development The Database Application Lifecycle A Relational

Database Development The Database Application Lifecycle A Relational Approach

Broad Goals of Database Development • Develop a common vocabulary • Define data meaning • Ensure data quality • Provide efficient implementation

Overview of the Db. DLC

Database Application Lifecycle Database Planning • Focus on management activities • Activities include: – Work to be done – Resources available – TORs – “Surely we can spend a few minutes before rushing off to spend our money or write programs. Isn’t that extra hesitation the essence of design” – Gerald Weinberg

Database Application Lifecycle System Definition • • Scope Parameters Application areas User groups

Primary Education Application Areas Facilities Teaching & Learning Materials Teachers Finance Learners

What is requirements analysis? • The process of defining your system. • A process of: – – Discovery Refinement Modelling Specification

Goals of Requirements Analysis • to determine the data requirements of the database in terms of primitive objects • to classify and describe the information about these objects • to identify and classify the relationships among the objects • to determine the types of transactions that will be executed on the database and the interactions between the data and the transactions • to identify rules governing the integrity of the data

Principles of Analysis • Understand the problem domain • Define the software functions to be performed • Represent behaviour of software • Model details of data, information, controls flows & functional behaviour in a layered manner • Move from functions & information outputs towards processing functions & information structures

Focus on PEOPLE Stakeholders System Owners System Users System Designers System Builders Vendors and Consultants Focus on DATA Focus on PROCESSES Focus on INTERFACES Building Blocks of An Information system System owner’s View of processes System owner’s View of interfaces System users’ View of processes System users’ View of interfaces Designers’ View of Data System designers’ View of processes’ System designers’ View of interfaces System builders’ View of Data System builders’ View of processes System builders’ View of interfaces System owner’s View of Data System User’s View of Data INFORMATION TECHNOLOGY & ARCHTECTURE Database Technology. Process Technology. Interface Technology

Focus on PEOPLE Stakeholders Focus on DATA Business Knowledge System Users Data Requirements System Builders Vendors and Consultants Focus on INTERFACES Building Blocks of An Information system System Owners System Designers Focus on PROCESSES Database Models Database Programs Database Management System

Requirements Discovery Methods • Collecting facts from existing Documentation • Research and site visits • Questionnaires • Interviews • Discovery prototyping • Joint Requirements Planning

Database design • The process of creating a design for a database that will support the enterprise’s operations and objectives

Database Design • Objectives: Develop detailed technical specifications for hardware, software, data, people and procedures--How the system will be built • End Result: Make or Buy? Detailed file/database design, program specs, interface design, sizing and response time specs • Methods: CASE tools, End User Computing • Skills/Talents Required: Technical • How to Avoid Risk: Careful check vs. functional requirements, management review

Database design goals v. Satisfy the users’ content requirements v. Ensure the consistency and integrity of data v. Provide a natural easy to understand structuring of information v. Satisfy the user’ performance requirements

Database Design Framework • Determine the information requirements • Analyse the real-world objects that you want to model in the database • Determine primary key attributes • Develop a set of rules that govern how each table is accessed, populated and updated • Identify relationship between the entities • Plan database security

Goals for Collecting and Analysing Data. • Identify major functions and activities of your organisation • Identify the objects of those functions and activities • Identify the characteristics of those objects • Identify certain relationships between the objects

Students and courses

Identifying entities • • • Students Courses Instructors Student. Courses Advisors

Identifying attributes • What information on each entity should we know? • Students(student_id, Fname, lname, phone, advisor_id) • Advisors(Advisor_id, Advisorname, Advisorphone) • Instructors(instructor_id, Instructorname, Instructorphone) • Student. Courses(Student_id, Course_id) • Courses(Course_id, Coursedescription instructor_id)

DBMS Selection • The selection of an appropriate DBMS to support the database application

Factors to consider • • Performance Ease of restructuring Integrity constraints Security

Development Alternatives Difficulties ØOperational system is produced late ØRush to begin implementation ØRequirements are difficult to capture Alternative methodologies ØSpiral approaches ØRapid application development Prototypes may reduce risk

Prototyping • building an experimental system (prototype: a preliminary model) rapidly and inexpensively for end users to evaluate • Using the prototype, end users can better determine information requirements. • planned iterative process of systems development • less formal – requirements determined dynamically as the prototype is constructed

Prototyping Determine Needs Build Prototype Evaluate Prototype No Acceptable Yes

Prototyping continued • advantages – useful when there is uncertainty about requirements or design solutions (decision-oriented solutions) – valuable for the design of the end-user interface – encouraging intense end-user involvement • disadvantages – – only suitable for smaller applications tending to skip essential steps in systems development hasty construction poor documentation

Implementation • Objectives: Implement system, fully-functional, deliverables in priority order, with effective training and conversion • End Result: Accurately functioning system, properly trained users • Methods: CASE tools, EUC • Skills/Talents Required: Technical, communication • How to Avoid Risk: Communication! Planning! Change management! Status reviews and walk-throughs!

Stages of Implementation • • • Hardware/Software Acquisition if needed Programming Testing (program, subsystem, system tests) Training (lead users, train the trainer) Conversion (in order of increasing complexity and risk) – – Parallel (old and new systems) Pilot (small scale, small scope) Phased (most critical functions first) Direct Cutover (with manual parallel operations)

Database Maintenance • Objectives: Fix “bugs” (incorrect program specs or code) in software, add enhanced functions, cycle back through SDLC phases as needed for small-scale projects • End Result: Fully Functional “Robust” System • Methods: As needed for phases above; audit the system • How to Avoid Risk: Watch changing business requirements, set priorities.