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Walkthrough:
When Jack opens his mashcal to create and event he is greeted with the homescreen shown on the Figure 2. It shows him to the events he has created day by day. He can transition to the new event creation window (also on Figure 2) on from the homescreen. He can name the event and choose its type as well as invite others and pickthe pick the possible dates for the event. Upon pressing on "Pick possible dates" button he will come to Pick Dates window shown on Figure 3. The structure of the picking dates window is similar to theiphone default alarm clock interface. The Month Week and Day can be set with scrollable selectors that move up and down with a flick (Similar to alarm choosing interface). The time slots can be marked available and unavailable and after selection clicking done button brings Jack back to the event creation window. He can then select the invitees from his contact list (Shown on Figure 4). This interface is similar to iphone contact interface. He can add import contacts as well as search for them in the autocomplete search input box. He selects Bill from his contact list, however he did not previously have Kate's contact and he adds her as a new contact. By pressing the Done button he sends invitation to Kate and Bill. When Kate and Bill receive invitations, push notification will appear on their phone as shown on figure 5. They can just simply reply "I can not go" or they can choose the dates appropriate for them via the Pick Dates interface and send the reply back.
(Figure 2) 
(Figure 3) 
(Figure 4) 
( Figure 5)
Analysis:
Learnability-
Good: Couple of affordances are used in the interface to improve usability. Traditional affordances like arrows and buttons are natural to the user. Their behavior is consistent with way people think about them. The "Percentage of People RSVP-d " icon communicates whether the event was for a group or just for Jack by showing many human figures or just one. That icon is filled up according to how many people reply to the invitations. The thumb icon on the Pick Date window on Figure 3 tells the user that the time slot can be selected with a touch; this communicates the model of the interface to the user effectively. Another thing that helps with the usability is that everything that user can interact with is labeled accordingly. Therefore, a user will not be wondering which part of the interface corresponds to what task.
Bad: The Pick Date interface might be initially unfamiliar to users. 2 or 3 slide walk through to show how to select dates and time slots might be necessary.
Efficiency - Efficiency
Good: Searching for contacts and autocomplete box helps user invite people efficiently. Also the Scrollable selector for the dates is more efficient than traditional text input methods. For users who want to link their mashcal to their calendars like gcal "Linking calendar" option is available. They can also import contacts from other contacts lists. Additionally, history of previous events which would be incorporated to inviting people window will allow people to choose invitees from the list of previously invited people, making it efficient to reinvite people.
Bad: Due to the limited screen size of phone, the time slow selection can not show all the time slots in one window. A user has to scroll down and make a selection if he wants to choose 8pm for example.
Safety-
Good: The fact that things are selectable with a one single touch makes it easy to recover from errors. Say a user choose a wrong time slot when picking a date. She can then just simply press on that time slot again to unselect. Another thing that helps with safety is that the autocomplete in the search box. The user can easily select invitees from the list without making spelling errors. The history features which would be incorporated to inviting people window will allow people to choose invitees from the list of previously invited people. Therefore, reinviting people to an event is almost error-free.
Other-
We can play with Typography ( different fonts, sizes etc.) to solve the problem of not being able to see many time slots in one window. The use of green for available slot ( red for unavailale ) will help user easily pick the appropriate dates.
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