Design, Implementation and Maintenance The “lower end” of the lifecycle focuses on Detailed logical and technical specification of the system or system changes (Design) The acquisition of hardware and the creation of software (Construction) Getting the new system in the hands of its intended users with minimal business disruption (Implementation) Maintaining the effectiveness of the solution as the business evolves (Maintenance)

System Design Usual divided into Logical and Physical Logical Design A detailed conceptualization of “what” the system must do These are the functional requirements of the system Logical design differences from requirements analysis in level of detail and specificity

System Design Elements Output design Reports Files, transactions Input design Screens Input transactions or files Processing design What are the major processing logic and algorithms to be used? Database and file design Create the database schema Define key non-database files

System Design Elements (Con’t) High level physical design Telecommunications What are the detailed network and telecom requirements? Operations To run the system, what operational procedures must be put in place? Control and security What controls will be required to maintain the security and integrity of the system? Test Design A preliminary test plan must be created

Physical Design Specification of the system components necessary to implement the logical design Elements Hardware If new hardware is required, this is the place to specify it What is the system load going to be and is the existing hardware adequate? What are the storage requirements? Will new networking equipment be required?

Physical Design Elements (Con’t) Software Design Identification of individual programs or program modifications Design of programs Specification of inputs and outputs Specification of critical logical components Test Design This is the point where the testing plan must be finalized

Physical Design Elements (Con’t) Database Design The detailed specification of the database and any files is done here Telecommunication Design Detailed specifications done Sufficient to procure hardware or contract work Security and control

Design Phase Checkpoints Logical and physical designs should be reviewed carefully by all team members Walkthroughs and reviews of each subsystem Important for quality and to ensure design consistency Management Checkpoint A management checkpoint is critical Should review all aspects, including cost, ROI and schedule

Construction and Test Software is written or purchased Hardware is purchased All individual components of system are tested Integrated system is tested Detailed implementation plans are created and tested Training takes place

Software Development Structured Design A body of learning about what constitutes good programs Maintainable Error free Heuristics Modular Clearly defined module inputs and outputs, entry and exit points The opposite of spaghetti

Software Development (Con’t) Structured programming Specific techniques regarding naming, use of certain programming constructs Consistent with structured design Integrated Development Environments (IDE) Can significantly improve productivity Use of program walkthroughs Peer or senior programmer does detailed examination of code Less expensive way to find errors than testing

Software Development (Con’t) Chief programmer teams Teams organized around a senior programmer or architect Team includes Junior programmers Librarian Testing specialists Documentation and training specialists

Testing Must proceed logically from small units to large units Individual programs Subsystems comprised of groups of programs Complete system Implementation testing Stress or load testing

Testing (Con’t) Testing must be designed based upon test criteria Test data Must be constructed which will produce all possible outcomes Must ensure that all program paths are exercised Expected results must be documented And obviously compared with actual Testing automation tools exist

Implementation How do I get all of this installed and running? Elements Training people Converting data from old system to new Installing hardware Installing software Go/No go implementation test Where do we hit a point of no return?

Implementation Alternatives If system is an addition to existing environment, implementation should be simple If system replaces an existing system Big bang approach Quick, less expensive, more dangerous Phase in by module Phase in by part of business

Maintenance Maintenance is the “base of the iceberg” Often, the cost of maintaining a system is 5 times the cost of original acquisition Impact of design on maintenance Well designed and well structured systems are much easier to maintain This means that additional investments during design and construction will yield big benefits during maintenance “You can pay me now or you can pay me later”

Maintenance (Con’t) Maintenance processes should be managed much like new development Maintenance authorization should be management decision Use of SR/MR process Categorization of request Bug fix (level of severity) Enhancement Externally required Estimated effort and cost

Maintenance (Con’t) Maintenance should follow a methodology like new development Requirements analysis Design Code review Test plan and testing Implementation plan This should be scaled to the size of the maintenance System documentation should be maintained as well