School of Computing External Design
Document
CISC 498
Information Technology Project
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The purpose of an external design document is to communicate how the system will appear to its users, how it will interface with existing work processes, how it will interface with other pieces of software, and what kinds of work products are required by/produced by the system. The external design document is written from the perspective of a user. It does not specify how the system's features will be implemented.
Your external design should be created in cooperation with your customer. You should create low fidelity prototypes to help walk your customer through the design. External design is iterative; plan to revise and rethink in response to your customer's feedback.
External design helps to refine your understanding of requirements. Do not be surprised to find that your discussions of external design bring to light misunderstandings in the systems requirements, possibly requiring you to significantly rethink your design.
Your external design document should be about 20 pages in length, and should contain the following sections:
Introduction Give a high-level description of the
problem that your software is meant to solve. User interface design Describe the system from the point of
view of its users. Use whatever descriptive techniques are
best for describing your kind of system. E.g., use
screenshots to describe the user interface's appearance; use
state machine diagrams to describe the navigational
structure of the application (particularly useful for
web-based applications); use English text to describe the
system's operation. It is not necessary at this point to
have finalized the graphic design of your system, but the
structural elements of the system should be pinned
down. Usage scenarios Use scenarios to describe examples of
how the system will be used. Scenarios should exemplify
important usage cases. Use different scenarios to illustrate
different user roles. Prototype Briefly describe the low-fidelity
prototype you created. Give example screenshots/mockups (if
different from the screenshots shown under user interface
design.) Discuss your choice of prototyping technology
(e.g., HTML, flash, pen and paper.) Work products Describe work products required by
your system to operate (e.g.., any existing files that your
system requires as input.) Describe work products your
system produces (e.g., and files/documents that are created
as a result of using the system. This helps characterize
your system's boundaries. Integration with existing
processes Describe how your system operates
within the context of a broader process. This will
demonstrate that your system effectively fits within the way
your customer works. Feedback from customer Briefly discuss your customer's
feedback on your external design. Briefly give examples of
how the design changed as a result of your customer's input.
Specify any concerns that may need to be addressed via
further refinement. Requirements update Briefly specify any changes to the
system's requirements that have come as a result of the
external design process.