patterns & practices: App Arch Guide 2.0 Knowledge Base

Checklist - Presentation Layer

Design Considerations

• UI technology choice is based on application requirements and constraints.
• Relevant presentation layer patterns such as Template View pattern are identified and used in the design.
• The application is designed to separate rendering components from components that manage presentation data and process.
• Organizational UI guidelines are well understood and addressed by the design.
• The design is based upon knowledge of how the user wants to interact with the system.

Caching

• Volatile data is not cached.
• Sensitive data is not cached unless absolutely necessary and encrypted.
• Data is cached is a ready to use format to reduce processing after the cached data is retrieved.
• Local caches are not used if your application is deployed in Web farm.

Composition

• Dynamic layouts are avoided, when possible.
• Abstraction patterns are used to avoid dependencies between components.
• Composite View pattern is used if you need to compose views from modular, atomic components.
• Template View pattern, through the use of Master Pages, is used to create consistent, reusable, dynamic web pages.
• Publish/Subscribe pattern is used for communication between dynamically loaded modules.
• Command pattern is used to support menu and command-driven interaction.

Exception Management

• Sensitive data or internal application details are not revealed to users through error messages or in exceptions that cross trust boundaries.
• User-friendly error messages are displayed in the event of an exception that impacts the user.
• Unhandled exceptions are captured.
• Exceptions are not used to control application logic.
• System exceptions and business errors are identified.
• Exceptions are logged to support troubleshooting when necessary.

Input

• Forms-based input is used for normal data collection.
• Document-based input is used for collecting input in Microsoft Office–style documents.
• Wizard-based input is used for complex data collection tasks or input that requires workflow.
• Device-dependant input, such as ink or speech, is considered in the design.
• Accessibility was considered in the design.
• Localization was considered in the design.

Layout

• Templates are used to provide a common look and feel.
• A common layout is used to maximize accessibility and ease of use.
• The layout considers device-dependent input, such as touch screens, ink, or speech.
• If you are designing a web application, Cascading Style Sheets (CSS) are used wherever possible for layout.
• Design patterns such as MVP are used to separate layout design from interface processing.

Navigation

• Navigation is separated from UI processing.
• Toolbars and menus are designed to help users find functionality provided by the UI.
• Wizards are used to implement navigation between firms in a predictable way.
• If navigation state is needed across sessions, the application is designed to persist navigation state.
• Command pattern is used to handle common actions from multiple sources.

Presentation Entities

• Presentation entities are used only if you need to manage unique data or data formats in the presentation layer.
• Presentation entities do not contain business logic.
• Custom classes are used to map data directly to business entities.
• Platform-provided classes, such as DataSets or Arrays, are used for data-bound controls.
• Presentation entities contain input validation logic for the presentation layer.

Request Processing

• Requests do not block the UI.
• Long running requests are identified in the design and optimized for UI responsiveness.
• UI request processing are unique components and are not mixed with components that render the UI or components that instantiate business rules.
• Passive View pattern is used to design interfaces that do not manage a lot of data.
• Supervising Controller pattern is used for interfaces that manage large amounts of data.

User Experience

• UI responsiveness is considered in the design. For instance, rich clients don’t block UI threads and Rich Internet Applications avoid synchronous processing.
• AJAX is used if you are building a web application and user responsiveness is important.
• The design has identified key user scenarios and has made them as simple to accomplish as possible.
• The design supports personalization, localization, and accessibility.
• The design empowers users, allowing them to control how they interact with the application and how it displays data.

UI Components

• Platform provided controls are used except for where it is absolutely necessary to use a custom or third party control for specialized display or input tasks.
• Platform provided data-binding is used where possible.
• Custom controls are created extending existing controls.
• State is stored in platform provided state management features, such as ViewState, for ASP.NET applications.
• Presentation Model pattern is used to manage UI state in WPF or Silverlight applications.

UI Processing Components

• UI process components are created only when necessary.
• If the UI requires complex processing, UI processing has been decoupled from rendering and display into unique UI processing components.
• If the UI requires complex workflow support, the design includes unique workflow components that use a workflow system such as Windows Workflow.
• UI processing has been divided into model, view and controller or presenter by using the MVC or MVP pattern.
• UI processing components do not include business rules.

Validation

• The application constrains, rejects and sanitizes all input that comes from the client.
• Server-side validation is used to validate input for security purposes.
• Client-side validation is used to validate input for user experience purposes, for instance to give the user error messages after receiving poor input.
• Built-in validation controls are used when possible.
• AJAX is used in Web applications to provide real-time validation.
• Validation routines are centralized, where possible, to improve maintainability and reuse.