The WebApp Design - Attributes, Goals and Web Design Pyramid

Design is an engineering activity that leads to a high quality product. The major attributes of quality for web applications are:
- Security : The main emphasis of security is the ability of the web application and its environment to avoid unauthorized access or attack.
- Availability : Web application will not meet users needs if its unavailable. Availability is the measure of the percentage of time that a web application is available for use.
- Scalability : Is the variation in volume handled significantly by the web applications and the system. It is important to build a web application that can accommodate the burden of success.
- Time to market : It is a measure of quality from business point of view.

What should be considered when assessing content quality?
- Scope and depth of content be easily determined so that it meets user's needs?
- Background and authority of content's author be easily identified?
- Possibility of determining the currency of content, last update?
- Stability of content and location?
- Credibility of content?
- Uniqueness of content?
- Is content well organized?
- Is content valuable?

Design Goals

The design goals for every web application are:
- Simplicity
- Consistency
- Identity
- Robustness
- Navigability
- Visual appeal
- Compatibility

Web Design Pyramid

Each level of the pyramid represents the design activities:
- Interface Design : It describes structure and organization of the user interface. It includes screen layout, interaction modes, navigation mechanisms.
- Aesthetic Design : It describes the look and feel of the application.
- Content Design : It defines layout, structure and outline of all content.
- Navigation Design : It describes the navigational flow for web application.
- Architectural Design : It represents the overall hypermedia structure.
- Component Design : It develops detailed processing logic.

What are different user interface design principles and guidelines in software engineering ?

A good web application interface is understandable and forgiving, providing the user with a sense of control. The inner workings of the system are not for concern for the users. Effective applications perform a maximum of work, while requiring a minimum of information from users.

USER INTERFACE DESIGN PRINCIPLES AND GUIDELINES

- Consistency of actions should be required in similar situations. The use of navigation controls, menus, icons should be consistent throughout the web application.
- Anticipation Web application should be designed in such a way that it should interpret the user's next move.
- Communication Whatever activity that is been initiated by the user, it should be communicated by the interface. Communication can be obvious or subtle. User status and location should also be communicated by the interface.
- Efficiency Users work efficiency should be optimized by the design of the web application and its interface and not the efficiency of the web engineer who designs and builds it.
- Flexibility Flexibility of the user interface should enable some users to get the tasks done directly and some other users to explore the web application in random fashion.
- Controlled Autonomy User movement should be facilitated by the interface in such a manner that enforces navigation conventions that are established for application.
- Focus The interface of the web application should be focussed on user tasks at hand.
- Human Interface Objects Use reusable human interface objects. An interface object that is seen, heard, touched by the end user can be get from the object libraries.
- Learn ability Learning time should be reduced by a well designed web application interface.
- Latency Reduction The web application should use multitasking so that the user can proceed with his work and do not wait for some internal operation to get completed.
- Metaphors A metaphor should call images and concepts from user's experience, but it does not need to be an exact reproduction of real world experience. The web application interface that uses an interaction metaphor is easier to learn and use.
- Maintain work product integrity A work product must be automatically saved so that there is no loss of information if an error occurs.
- Readability Every person should be able to read the information in the user interface.
- Track State The state of the user interaction should be saved and stored so that the user can return to the same point even if he or she logs off.
- Visible navigation A well designed web application interface provides the illusion that users are in the same place, with the work brought to them.

Object Oriented Hypermedia Design Method (OOHDM)

Object Oriented Hypermedia Design Method (OOHDM) is a method for designing web applications. The development of hypermedia applications consists of four different design activities :

- Conceptual Design for OOHDM
In conceptual design, a conceptual schema is built that represents objects, relationships and collaborations existing in the target domain. To create class diagrams, aggregations and class representations, diagrams and other information, Unified Modelling Language(UML) is used.

- Navigational Design for OOHDM
In OOHDM, the navigational design is build over the view of conceptual design. It uses a predefined set of navigation classes like nodes, links, anchors and structures. Navigation design is expressed in two schema's, the Navigational Class schema and the Navigational Context schema.
Objects that are derived from classes defined in conceptual design are called navigational objects. A series of navigational classes or nodes are defined to encapsulate these objects.
Navigational design must take into account the way in which the user explores the hypermedia space.

-Abstract Interface Design
Abstract Interface Design specifies the interface objects. To represent the relationship between interface and navigation objects, a formal model of interface objects called Abstract Data View is used. The abstract data view defines:
- a static layout.
- behavioral component.

- Implementation
Any application-specific model, like OOHDM design, must be eventually implemented using an implementation technology. This activity represents a design iteration that is specific to the environment in which web application will operate.

Hypermedia Design Patterns in Web Engineering

Web engineering uses design patterns. These are of two types:
- Generic design patterns - applicable for every software.
- Hypermedia design pattern - specific to WebApps.
Design problems can be solved by using design patterns. There are some pattern categories:

NAVIGATION PATTERNS
These patterns helps in the design of NSU, navigation links and overall navigation flow of the web application.

ARCHITECTURAL PATTERNS
It helps in the design of content and web application architecture. Many architectural patterns are available for web engineers who design web applications in various business domains.

COMPONENT CONSTRUCTION PATTERNS
The web application components can be combined by the methods provided by these patterns. When data processing functionality is required within a web application, the architectural and component level design patterns are applicable.

PRESENTATION PATTERNS
Presentation patterns assist in the presentation of content as it is presented to the user via the interface. They tell how to organize user interface control functions, shows the relationship between an interface action and the content object it affects, establish content hierarchies.

BEHAVIOR AND USER INTERACTION PATTERNS
These patterns assist in design of user machine interaction. They address how the interface informs the user of the consequences of a specific action, how a user expands content based on usage context, how to best describe the destination that is implied by a link.

The Risk Mitigation, Monitoring and Management (RMMM) Plan

The Risk Mitigation, Monitoring and Management, RMMM, plan documents all work performed as part of risk analysis and is used by the project manager as part of overall project plan.
The goal of the risk mitigation, monitoring and management plan is to identify as
many potential risks as possible.It is the organization’s responsibility to perform risk mitigation, monitoring, and management in order to produce a quality product.
Every phase of this plan is of equal importance. More focus is maintained in the initial phases i.e. the identification and assessment of possible risks.
Once RMMM has been documented and project has begun, risk mitigation and monitoring steps commence.
Once RMMM has been documented and the project has begun, risk mitigation and monitoring steps commence.
The measurement of effectiveness of these mitigation / contingency plans should be well carried. It must ensure that after the execution of such plans the risk exposure is reduced or preferably eliminated.

- Risk Mitigation covers efforts taken to reduce either the probability or consequences of a threat.
- Risk monitoring and control is the process of identifying, analyzing, and planning for newly discovered risks and managing identified risks.
- Risk management is the identification, assessment, and prioritization of risks.

Software Six Sigma for Software Engineering

Software Six Sigma is a strategy to enhance and sustain continuous improvements in software development process and quality management. It uses data and statistical analysis to measure and improve company's performance by eliminating defects in manufacturing and service related processes.

ATTRIBUTES OF SIX SIGMA

- genuine metric data.
- accurate planning.
- real time analysis and decision support by the use of statistical tools.
- high quality product.
- software improvement costs and benefits.

STEPS IN SIX SIGMA METHODOLOGY

- Customer requirements are defined, project goals via well defined methods.
- Quality performance is determined by measuring existing process and its output.
- Analyzing the defect metrics.
- Process improvement is done by eliminating the root causes of defects.
- Process control to ensure changes made in future will not introduce the cause of defects again.
These steps are referred to as DMAIC(define, measure,analyze,improve and control) method.

- Design the process to avoid the root causes of defects and to meet customer requirements.
- Verify the process model will avoid defects and meet customer requirements.
This variation is called DMADV(define, measure, analyze, design, and verify) method.

The COCOMO II (Constructive Cost Estimation Model) Model

COCOMO II is an extension to the COCOMO model. COCOMO II takes into account new development processes, increased flexibility in software development, need for decision making with incomplete information and new data about projects.

COCOMO II is really three different models :
- The Application Composition Model used for prototyping.
- The Early Design Model used when requirements are available but design has not yet started.
- The Post-Architecture Model used once the system architecture has been designed.

COCOMO II models require sizing information. Three different sizing options are available as part of the model hierarchy i.e. object points, function points, and lines of source codes.
The application composition model uses object points which is an indirect software measure that is computed using counts of the number of screens, reports and components likely to be required to build the application.

DIFFERENCES BETWEEN COCOMO I AND COCOMO II

- COCOMO I requires software size in KDSI as an input, but COCOMO II is based on KSLOC.
- COCOMO I provides point estimates of effort and schedule, but COCOMO II provides likely ranges of estimates.
- In COCOMO II, the estimation equation exponent is determined by five scale factors instead of three.
- Data points in COCOMO I: 63 and COCOMO II: 161.
- COCOMO II adjusts for software reuse and re-engineering but COCOMO I made little accommodation for these factors.