...
The user would click prioritize on a vocab or grammar item if he wants to see more sentences of that sort (because he wants to practice reading more sentences that use that particular vocab or grammar), and deprioritize if he doesn't want to see sentences that use that vocab item or grammatical pattern. If the user clicks on prioritize for some vocab word or grammatical pattern, then among the sentences later in the list (which haven't yet been read), the ones that use the vocab or grammar that the user wants to prioritize, will be moved up and injected immediately below the sentence that the user just read (the sentences associated with the accordian menu from which the "prioritize"/deprioritize button was clicked). That way, the next sentences that the user reads will all use the particular grammatical pattern that was prioritized. If the user clicks on deprioritize, then later sentences using that grammatical pattern will be moved to the end of the list, so that the user will see those only after having read all other sentences.
If Joe wants to see the entire sentence romanized, he can expand the "Show romanization" accordian menu. Likewise, if Joe wants to have the English translation of a sentence displayed, he can expand the "Show English translation" accordian menu. If Joe does not understand some grammatical aspect of the sentence, or simply wants more practice with a grammatical form (in the scenario, the -tai verb conjugation), he can expand the Grammar accordian menu. Here, he will find the listing of grammatical aspects that are used in this sentence, and he can press "prioritize" on "-tai verb conjugation" so that the sentences using that grammar get moved up to where he is reading at, so that the next sentences he reads utilize the grammatical pattern.
If Joe encounters a sentence whose grammar patterns listed are incorrect, then he can expand the accordian menu, and click the "edit" button. Here, he can remove any categories that are incorrect (or add any that need to be added), and click "done editing" to save changes.
If Joe wants to contribute a sentence, he goes to the home page, and switches to the "contribute" tab. Here, he selects the language of the sentence he'll contribute from a pull-down menu, and enters the sentence itself and its translation in a textbox. Then, he selects any additional grammatical tags that would be used to help users find his sentence, clicks on "add" to add them, then clicks on "contribute sentece" to contribute the sentence. Now, any user who subsequently clicks the "more sentences" option on that type of grammatical tag will have Joe's sentence displayed to them among the list. (The usage of tags for representing the grammatical patterns found in a particular sentence is used to simplify the backend, to avoid needing to use NLP to determine the grammatical structures found in sentences. Locating vocabulary in a sentence should be considerably easier from a backend standpoint, and hence sentence contributers don't need to tag sentences with the vocabulary they contain, only the grammatical patterns).
Usability Analysis
Learnability
The lack of needing to perform any registration or select options other than the language before being able to read sentences enhances the ease of use. Additionally, the interface for browsing sentences is simply a list of sentences, hence the user doesn't need to know what he's looking for (ie no need to know the name of the particular grammatical structure) to find reading material.
The prioritize/deprioritize model for filtering sentences is also more easily learnable than something like an explicit search for sentences containing particular words, as the user doesn't need to be able to recall, the vocabulary words and sentence patterns that he wants to review - he just needs to be able to recognize them when they come up in the list of sentences.
The per-sentence information gathering process makes heavy use of accordian menus. These are becoming fairly common in web apps, and hence learnability with their usage should not be an issue. The usage of the clicking on a part of a sentence to expand out the accordian menu for that vocab item, however, is somewhat inconsistent with the users' experience of how accordian menus work. Namely, users may not expect accordian menus to expand by themselves if the user clicks elsewhere. Additionally, the highlighting of an item in an accordion menu may not be noticed by the user, because it occurs far from where the focus of the user's attention (the mouse) is. However, this is a tradeoff for internal consistency, as it ensures that no separate popup or hover-over information dialog is needed if the user wants information about some particular word in the sentence - all supplemental information for a given sentence is displayed in its accordian menu.
Another learnability issue is that it may be difficult for a sentence contributer to know what each of the grammatical tags mean, particularly because differing textbooks may describe different sentence patterns using different terminology.
Efficiency
This interface is not efficient for users who already know what particular type of vocabulary or grammatical pattern they want to practice, as they must first find an example of a sentence using that vocab or grammatical pattern before they can click on the "prioritize" button to bring up additional sentences using that particular vocab or grammar. However, because of the choice to order sentences such that the ones using grammar and vocabulary introduced in recent chapters (which is likely what the user wants to review) come first, then finding such a sentence will not take long in the case when the user is practicing material introduced in recent chapters (which is likely the most common use case).
Another issue with efficiency on the initial screen is that a selector is used to locate the textbook, which, while necessary if the user is able to recognize but not recall their textbook name, may be less efficient than typing a name with autocompletion for users who already knows the name of their textbook .
The choice of a selector box for adding grammatical tags to sentences, while easily learnable because all of the grammatical tag types are visible, may be inefficient for users who already know the category the word belongs to. While the grammatical could be sorted alphabetically, a user might know the particular grammatical pattern under a different name from the terminology that is used in this website. Hence, it may make sense to also allow a search box with autocomplete to be used for searching for particular tag types. Optimally, users shouldn't even have to input what types of grammatical structures in a sentence, but this would unfortunately involve complex NLP work for detecting grammatical patterns in sentences.
Visibility
This design's state is encapsulated in the ordering of the list of sentences, which is always visible to the user. While information about the sentence's vocabulary, grammar, romanization, and translation are hidden in the accordion menu by default, this is by design, because it is meant to be relied on only if the user has trouble reading the sentence without assistance.
Error Prevention
One particularly problematic error a user might encounter is if he accidentally presses "deprioritize" on a vocabulary item or grammatical structure that he actually did want to review. What happens in this case is that sentences containing it will go to the very end of the list, and he won't see them until then. Thus, such an error is not easily undo-able (the user would need to go to the end of the list, and press "prioritize" on the item again, but in the process would lose his reading position). This is an example where design 3, which uses popups to display supplemental materials (and can thus just be closed if accidentally opened), has an advantage over this one.
The editing functions - namely, adding and removing grammatical tags from sentences, and changing translations for sentences, are unfortunately not undoable. For this reason, because this model functions much like a wiki - in that any user is able to edit or contribute any sentence - it may be necessary to introduce some form of history into the interface should accidental editing or vandalism become a problem.
Design 2
Storyboard
This design provides the student user with a ‘home’ view (Figure 2) of all the textbooks that he is learning from. A user can add and search textbooks from any page by using the ‘Add/Search’ bar labeled in Figure 2. The user can either search for a title (Figure 4), or see an alphabetical sorting of all the textbooks in the system (Figure 3). Also, there are language filters along the right to allow the user to narrow his search. After the student has added the book to his textbooks, he can return to his ‘home’ via the ‘My Home’ link that is located at the top of every page and then pick a book from his selections.
...
Key Concepts: Every new state (any new page brought on by a button/link click) will be displayed in a new window (pop-up window)
Page 1:
This is the homepage that greets users coming on to the site. The page will have 2 options: for old users to log in with username and password, or for new visitors to sign up by entering a username, email, and password (with a password confirmation). The button at the right of the confirmation password textbox will be labeled "register." If the username is already in use, the page will prompt the visitor to try a different username. After an account has been created, the visitor will have to log in using the normal log in. 
Page 2:
The homepage will enter into "page 2" after visitor successfully logs in. The user now has two options. Clicking the "Language QuickGo" button will lead the user to "page 4." The user can also click the "textbook go" button to enter "page 3." The "Language QuickGo" button is only available for clicking after the user enters the language in the language drop-down list. The "textbook go" button is only available after the user selects the language, textbook name, and chapter. Note, this will be almost identical in format to the MIT coop textbook selection.
Page 3:
The user will arrive upon this page after filling in the appropriate selections and clicking the "textbook go" button. This page will contain a series of boxes, each containing a single practice sentence provided by the textbook publisher as supplementary material for that chapter. Each sentence box will contain a button labeled "?" at the bottom left corner. Clicking on this button will cause a page to pop up. The page will contain three headings: tags, romanized, and english translation. Below the tags heading will be a series of hyperlinked tags pertaining to each work in the sentence. Below the romanized heading will be a phonetic description of the sentence (allowing the user to pronounce the sentence). Finally, below the english translation heading will be the english translation of the sentence. Clicking any of the hyperlinked tags under the Tags heading will take the user to "page 5." The "cancel" button closes the pop-up page and returns the user to the original "page 3" containing the list of supplementary sentences.
Page 4:
The user can arrive upon this page after clicking the "language go" button instead of the "textbook go" button. This page serves two function. The first function is to allow the user to find example sentences after entering certain tags in the textbox with the heading "Tag Search" and hitting the "Go" button. This will take the user to "page 5." The second function of this page is to allow experienced foreign language speakers to add sentences to the database. The user must type in a sentence in the preselected foreign language, enter a list of words to tag the sentence in the textbox labeled "Tags," and finally enter the same sentence in English in the textbox labeled "English Translation." The user can then hit the "Add" button to add the sentence. The "Add" button only becomes available after all three textboxes are completed. Hitting "Add" will clear the textboxes (information scent for user to know the system has added the sentence) and add the sentence/sentence info to the database.
Page 5:
This page can be arrived on by the user in two ways. The first way is when the user clicks on a hyperlinked tag. The second way is by the user entering tags in the tag search box on "page 4." There are several notable components to this page. First, the Tag: label will contain the tag(s) that were used to take the user to the current page. Next, definitions (translations) will be provided for the Tag in the "Def" field. Below will be a scrollable list of example sentences associated with the tag. Each sentence will have an "edit" button at the end. Note that these user-provided sentences differ from the textbook-provided sentences on page 3 because the tags can only be added/removed in user-provided sentences. Clicking the "edit" button will bring up a pop-up page with three notable components and two buttons. The first component is the Tag List, which has an editable text box containing all the tags associated with the sentence. The user can add and delete tags in the textbox and click the "update" button to confirm those changes. The second component is labeled by the heading "English Translation" and is a translation of the sentence. Finally, the third component is the Tags (hyperlink) component allowing the user to go to more "page 5"-type pages. Clicking the "update" button will also update the hyperlinks available in the Tags field (the third component of the pop-up page). Clicking the cancel button will close the pop-up page. 
Learnability
Pros:
The interface is very simple. The existence of cancel buttons give users a more clear understanding of how to exist out of a pop-up page. The existence of pop-up windows allow the user to switch views easily via the interface provided by the user's OS for switching among windows (something user should be used to and familiar with). Certain buttons are only clickable when the necessary fields are completed, enforcing certain actions.
...
Allowing users to freely modify the tag list of user-contributed example sentences can be dangerous. Does not have a safety for when users accidentally modify and update the tag list field of user contributed example sentences.
Key Differences
...
between Designs
Overall Interface:
Design 1: This design consists of a single and simple standalone page. The vocabulary and grammar that the user wants to read is represented by the order of the sentences in the list. Vocabulary and grammar included in the sentences directly below the currently being read sentence are the ones that the user wants to practice reading.
...
Design 3: This design provides the user with an interface that hides complexity. A common theme is that extra information is displayed only upon actions (such as clicks) by the user (e.g. if a user wants to reveal additional information about a sentence, he can click the question mark button to open a new window, this window in effect encapsulates the extra information so that is easy for the user to hide/show).
Finding Reading Material:
Design 1: The user does not explicitly search for particular vocab or grammatical items. Rather, the user is displayed a list of sentences, and he uses prioritize and de-prioritize operations on vocabulary and grammar items to reorder the reading list to make grammar and vocab he wants to practice appear below where he is currently reading, and to exclude vocab and grammar he does not want to read.
...
Design 3: Readings are listed in reading blocks. Each block has one sentence and an options button, which provides more info on the sentence in a new window. So reading sentences and extra information is separated.
Contributing Reading Material:
Design 1: Sentences are added via a tagging system. A separate interface, apart from the listing, which can be entered from the front page, is used.
Design 2: To add words, the user must be look up the word in the chapter (either by list view or search view), then make an entry for the specific vocab.
...