California Digital Library
User Interface Principles
When selecting information services vendors on behalf of the entire University of California, the CDL prefers vendors who meet our standards of quality.  We use the following principles when evaluating a user interface, in combination with the more detailed requirements laid out in the following documents:
•	Technical Requirements for Database Vendors 
•	Technical Requirements for E-Journal Vendors
•	Web Accessibility Initiative Guidelines  
Consistency & Clarity
•	The interface should use consistent language and tone throughout, with words, phrases and concepts familiar to users, rather than system-oriented terms. It should follow real-world conventions, and information should appear in a natural and logical order.  Example:  Use “Subject” as the label for Subject searching rather than “Descriptors”.
•	Users should not be presented with irrelevant or rarely needed information and/or graphics. Every extra unit of information in a dialogue competes with the relevant units of information and diminishes their relative visibility.   Example: The interface should not contain distracting graphic icons.
•	The same words/commands should perform the same functions throughout the interface.  Users should not have to wonder if different words, situations, or actions mean the same thing.  Example: Clicking on a “modify search” link from any point in the search results display should take the user back to the same menu of search modification choices.
•	Functions of words/commands should be consistent with widely accepted standards.   Example: Search options (such as Keyword, Boolean, etc.) should function as expected.
•	Icons or words/commands indicating actions and options should be clearly differentiated so that users can readily tell them apart.  Example: Labels for items such as full text and citation should appear with the icon.
Context & Navigation
•	The interface should be structured so that, at any given point, users can identify where they are in relation to the supported options and functions.  Users should not have to remember information from one part of the dialogue to another.  Supporting tools and search features should be incorporated into the most common user task sequences.  Example:  Tabbed search screens where a tab’s label and emphasis indicates the search type being used, or an on-screen display of the status, e.g., “Advanced Search.”
•	Links should clearly indicate to users where they will end up, preventing errors.  Example: A link to details on how to use a thesaurus should be labeled “Go to Thesaurus Help” rather than “More Info.”
•	Instructions for use of the system should be visible or easily retrievable whenever appropriate.  Example:  The options for features such as Search or Help should be readily available so the user does not have to remember how to navigate to them. 
•	It should be clear how to exit or back up from an activity at any point in the process.  Users often choose system functions by mistake and will need a clearly marked "emergency exit" to leave the unwanted state without having to go through an extended dialogue. Examples: Functions such as Undo and Redo should be clearly marked; for functions that open new browser windows, the procedure for closing the window should be obvious.
Search
•	The interface should aid in the process of creating a search statement, and should provide multiple ways for users to intuitively refine a query by grouping, sorting, and limiting from the results page.  Examples: Suggestions for broadening or narrowing a search by language, format, etc. should be made; users should be able to select options from a list of controlled vocabulary.
•	The system should offer choices from a menu of pre-defined syntaxes, for both searching and navigating thesauri.  Users should not have to guess at syntaxes.  Example:  Multiple pull-down menus with the choices AND, OR, NOT etc. should be offered to combine search terms.
•	Documentation of the range and scope of searchable materials must be easy accessible.  Example: Providing a link to the list of Journal Titles indexed in the database directly from the search interface.  
“Learnability” & Flexibility
•	There must be a minimal learning curve for first time users, and as well as provisions for more advanced users to learn features as they become appropriate.  Example:  Both simple and advanced search modes should be available.  
•	Mechanisms should be available to speed up the interaction for expert users; the system should cater to both inexperienced and experienced users.  Example:  A Command line interface that allows advanced users to accomplish their searches more quickly and concisely than is possible via the graphic user interface.
•	Help and documentation should be easy to search, focused on the user’s task, list concrete steps to be carried out, and should not be unwieldy.  Examples: Documentation should be readily available on each page or just a click/page away; definitions of terms should be provided. 
•	The system should always keep users informed about the status of reported problems through appropriate feedback within a reasonable time.  Example:  If a patron cannot access a particular database because of a licensing agreement condition, this should be clearly stated instead of simply denying access without an explanation.
•	Error messages should be expressed in plain language, precisely indicate the problem, and constructively suggest a solution.   Example: The system should suggest search strategies when it retrieves too few or too many search results.
Personalization
•	User defined display options should be available.  Example: Users should be able to change the size of icons, or choose a certain number of results to display.