Reveal relationships among and between the four major system components:  external entities, processes, data stores and data flows between these giving the functional perspective focuses on processes rather than on objects and physical entities

Is the source or destination of data, while the former provides data from data stores (tables, views, files) and the latter receives and loads data into data stores or create in-memory datasets?

Is a defined sequence of transforming data (e.g. cleaning, distributing, merging, summarizing, updating), performing computations, making decisions (logic flow) or directing data flows based on set of rules (written as: if <condition> then <consequence>).

Represents the storage (files, tables) of persistent data required and (or) produced by the process for later retrieval by the same process or an- other one.

Represents the directed path of data, acts as an interface between DFD components and can include a single or multiple sources (destinations).

Is a visual presentation of components (e.g. forms, controls, labels), arranged, selected and pinpointed in precise and persistent localization to describe its appearance

Contains common, problem-solving and component-oriented guidelines for designers and users community

Is a sequence of actions, conducted to accomplish in- tended goals.

A prototype can be used to illustrate that designed idea is functional, expressing its qualities in a visual and interactive way, also to prove its merit or value and motivate team members to think about the problem from different perspective;

If designing interactive software, we usually create mock- up and demonstrates how something will be used and how we can interact with it; in a few cases, particular mock-ups are tied to a usability study, where parts of the prototype can be evaluated in a structured way or just serve as a mean to roughly express to a developer how something should look or work

Developers may take into account different implementation approaches, coding techniques and finally programming languages, within each available technology platform has its own biases and preferences; in this case a prototype represents an exploration into which technology will support certain UI/UX features

Useful for expressing design concepts in the form of     UML or BPMN diagrams or as a free-hand sketches and drawings like Rich Picture

A structured description of user characteristics, task and organizational environment

Simulate operating an actual system on a computer screen; such prototypes are prepared with a specific software prototyping tools and they may be easily used for usability testing and for gathering new requirements from prospective users