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Unformatted text preview: 1/26/10 1 Design Methodology CSCI 264 Methodology Outline – Part 2 • Semantic design • Syntactic design • Lexical design Semantic Design • Design units of meaning between user and computer • These are not the interface elements • User computer – Detailed definition of commands for operating on objects, relations between objects, and attributes of objects • Computer user – Selection of what information needs to be presented to the user – Identify problems that can occur and engineer them out when possible Example Semantic Specification • Command: add_symbol_instance • Information (parameters) required: – Symbol_position – Symbol_identifier • Description: "An instance of the symbol is created and added to the figure at the designated position. The instance becomes the currently-selected object, so that succeeding operations apply to it. The previous currently-selected object is no longer selected." Example Semantic Specification (cont.) • Errors – The symbol_identifier is unknown (engineered out by use of menu for selected symbol) – The symbol_position is outside the viewport (engineered out by constraining positioning device to viewport) • Side effects – The previously selected object is deselected. • Feedback – The instance is seen on the display, and is highlighted because it is the currently-selected object. The previous currently-selected object is de-highlighted. Semantic Design Example – Input • Get entity (such as file, template,...): – Entity becomes current (detailed definition of command) – Must also identify semantic errors and determine the consequences if an entity does not exist 1) Entity created if doesn't exist 2) User is asked if entity should be created 3) Error if entity does not exist (separate create command must be used to create entity) • Note that the above cannot occur if files and lines are selected by picking rather than by naming • What happens if a user "picks" nothing? 1/26/10 2 Semantic Design Example – Output • Current file name - always • Size of current file - always • Current command - until completed • Results of last command - when completed • Current state - always – awaiting command – processing command • Error message - when occurs • All file names - on request • Help - on request Cleartune • Functionality: – produce a selected tone (pitch pipe) – recognize tone as note (tuner) Cleartune • Functionality: – produce a selected tone (pitch pipe) – recognize tone as note (tuner) • Objects – cleartune – pitch pipe – tuner – note Cleartune • Attributes – note • pitch (the frequency) • volume • Relationships – clear tune is a pitch pipe or a tuner • Roles – pitch pipe produces note – tuner measures pitch (frequency) Cleartune (semantic) • actions on objects – cleartune • turn on – pitch pipe • activate (side effect tuner is deactivated) • produce pitch – tuner • activate (side effect pitch pipe is deactivated)...
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This document was uploaded on 09/02/2010.
- Spring '09