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The overall design is pretty straight forward. Information is added within each section and immediately updated after being added so it'll be clear what does what. All the buttons have affordances that show they are clickable, and there is a consistent design on what an add button looks like. Edit links will show up next to items that can be changed. For tasks and documents, the items will look like they are clickable by underlining them. Deleting items are possible after getting to their edit menus. The website doesn't create any new widgets or items not already commonly found on the web, and an experienced web user should be able to navigate the site quite easily.
Visibility
The side panel allows for visibility of how information is treated within the website, companies are within groups, and task,documents, contacts are within each company. The design allows for quick access to all the tasks, contacts, and documents quite visibility through links in the navigation bar. However, it isn't clear from the design that the links in the navigation bar show all the contacts, tasks, and documents the user has uploaded. However after clicking on one it'll be apparent to the user what they do.
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The design is pretty efficient at looking up already stored information, there are various methods to find an item(i.e. contact, task, document). One can select the company it is affiliated with, from the companies link and then click the proper subgroups or clicking the navigational bar item that corresponds to the item. Each item in the navigational bar shows all the contacts/documents/tasks uploaded and are filterable if an user is looking for it. However, the design does not provide an efficient way to upload batch information. If the user has 100 companies each with contacts, tasks and documents there isn't an easy way to add all the items at once from this design. However, users who need to fill in on the order of 100 companies initially is not the main audience for this website.
Error Prevention
There are various aspects to prevent errors when adding companies existing groups are populated in the drop down, so an user won't accidentally adding similar groups. The dialog box will show an error when a company with the same name is entered again to prevent duplication. Errors in adding the information are easily correctable, however deleting things can't be undone. It will be apparent to the user when and what he/she is deleting when that happens, so it's highly unlikely there would be an error.