NN Group defines a complex application as 

"any application supporting broad, unstructured goals or nonlinear workflows.

In addition, complex apps frequently:

- Support highly trained users with specialized knowledge
- Help users navigate and manage large underlying data sets and enable advanced 
 sensemaking or data analysis
- Support problem solving or end goals with unknown or variable underlying tasks
- Require handoff or collaboration among multiple roles, tools, or platforms
- Mitigate the risks of executing high-impact (or high-value) tasks, where high loss (e.g., revenue or even lives) is at stake"

Many complex applications are focused on supporting specialized domains, where the work requires specialized background and training. 

Contrast this against generalized applications, where NN Group defines them as having the ability to "enable nonspecialized users to complete largely discrete, linear tasks organized around well-structured goals."



What is a Complex Application? 

This complexity refers to "the complexity of underlying technology, such as the interconnection of multiple and variable (often legacy) back-end systems or databases that support an application."

Having high integrative complexity can result in a bad user experience. If users have to continually perform boring and repetitive to obtain data, this is high integrative complexity. 

Integrative Complexity

"Intention complexity refers to the complexity associated with supporting the unstructured goals and broad tasks that characterize the usage of complex apps"

There is not always a knownw best path to complete a task. Also designers want to encourage an open-form style of interaction. It is difficult then to know the scope.

"This ambiguity and variance make it difficult to understand and design for realistic usage."

Intention Complexity

https://www.nngroup.com/articles/complex-application-design-framework/

Complex Application Design: A 5-Layer Framework

Information complexity in application design refers to the large data volume inherent in many complex applications and the interaction behaviors, such as exploring, filtering, zooming, and modeling, required to navigate and analyze these datasets. Designers must carefully manage the amount of information on screen to ensure it is relevant but not overwhelming, as excessive information complexity can be time-consuming and confusing for end users.

Information Complexity in Application Design

"Environmental complexity refers to the physical surroundings of complex-app users. These surroundings are often difficult to understand and design for without first hand, real-time field work." Interruptions in field work might be frequent, so it's important to start in-person testing and research early on.

Environmental Complexity in Application Design

"Institutional complexity refers to the cultural or microsocietal structures that exist within an organization, including norms, attitudes, roles, political tensions, sources of power, and institutionalized ways of doing things." Long-time users and domain experts often prefer legacy systems and established workflows over proposed changes. Because new designers typically lack the tenure and domain credibility of established staff, their input is frequently discounted or resisted by the organization, regardless of its merit.

Institutional Complexity

Apply the 5-layer complexity framework—Integration, Information, Intention, Environment, and Institution—to break down the sources of complexity that are most present in the system you are designing. Analyzing each layer separately helps UX designers and researchers avoid feeling overwhelmed and keeps the overall design goals in view.

Applying the 5-Layer Complexity Framework in UX Design and Research

When designing for a complex application, designers should consider 5 layers of complexity based on context for the application's use.

- Integration
- Information
- Intention
- Environment
- Institution

University of Michigan - Ann Arbor

- Tooltip Guidelines
- 10 Usability Heuristics for User Interface Design
- Visibility of System Status (Usability Heuristic #1)
- 5 Steps to creating a UX-Design Portfolio
- Complex Application Design: A 5-Layer Framework
- 8 Design Guidelines for Complex Applications
- Feature Richness and User Engagement
- Usability Heuristic #8: Aesthetic and Minimalist Design
- Social Media User Experience
- The Top Enduring Intranet-Design Mistakes: 7 Deadly Sins
- State-Switch Controls: The Infamous Case of the "Mute" Button
- Design Systems 101
- Interaction Cost
- Similarity Principle in Visual Design
- Design to Match the Medium
- Learnability vs. Efficiency in User Interface Design
- Cards: UI-Component Definition

Nielsen Norman Group Articles

"Tooltips are user-triggered messages that provide additional information about a page element or feature. Although tooltips aren’t new to the web, they are often incorrectly implemented."

Tooltip Guidelines

These 10 general principles for interaction design, created by Jakob Nielsen, are broad rules of thumb rather than specific usability guidelines.

1. Visibility of system status
2. Match between system and the real world
3. User control and freedom
4. Consistency and standards
5. Error prevention
6. Recognition rather than recall
7. Flexibility and efficiency of use
8. Aesthetic and minimalist design
9. Help users recognize, diagnose, and recover from errors
10. Help and documentation

10 Usability Heuristics for User Interface Design

"Summary: A portfolio highlighting your design process and past work shows others who you are as a designer. The process of creating a UX-design portfolio allows you to reflect on your skills and achievements."

- What Hiring Managers Are Looking For
- Putting It Together
- Navigating Roadblocks

5 Steps to creating a UX-Design Portfolio

Complex applications are extremely diverse. However, they do have general issues they can face, even across different applications. These 8 guidelines can help address those general issues and improve user efficiency.   
 
1. Promote learning by doing.
2. Help users adopt more efficient methods to do their tasks.
3. Provide flexible and fluid pathways through workflows.
4. Help users track actions and thought processes.
5. Coordinate transition among multiple tools and workspaces.
6. Reduce clutter without reducing capability.
7. Ease transition between primary and secondary information.
8. Make important information visually salient.

8 Design Guidelines for Complex Applications

Summary: "No. 8 of the top 10 UX design heuristics is to remove unnecessary elements from the user interface and to maximize the signal-to-noise ratio of the design."

Usability Heuristic #8: Aesthetic and Minimalist Design

There are elements within social media that make it compelling to use and it is a way for users to connect with people around the world without necessarily having to meet the person. Social media generates a way for users to reconnect with people from their past and haven't had the chance to interact with them in a while. 


Social Media User Experience

Intranet tools and programs come and go, but bad UIs linger for years, impact employee productivity and morale, and ultimately increase organizational costs.

The Top Enduring Intranet-Design Mistakes: 7 Deadly Sins

Summary: "On–off controls that switch between two different system states need to clearly communicate to users both the current state and the state the system will move to, should the user press that control."
- Two Pieces of Information, Two Controls
- Two Pieces of Information, One Control
- State-Switch Control Recommendations

State-Switch Controls: The Infamous Case of the "Mute" Button

"Summary: A design system is a set of standards to manage design at scale by reducing redundancy while creating a shared language and visual consistency across different pages and channels."

Design Systems 101

"Summary: The interaction cost is the sum of efforts — mental and physical — that the users must deploy in interacting with a site in order to reach their goals."

User actions that add to interaction cost can include scrolling, reading, looking around for information, page loads, typing, and etc.

Interaction Cost

"Avoid a one-size-fits-all approach to UX design. Consider the the strengths and weaknesses of each platform when presenting information."

For a great user experience, designers should try to take advantage of the strengths of each specific medium or platform, and do their best to overcome or avoid the weaknesses and limitations of each platform.

Design to Match the Medium

Summary: The most fundamental usability components or metrics are learnability, efficiency, memorability, errors, and satisfaction. This video focuses on two of these; learnability and efficiency. Although these two concepts. arerelated, there is an important distinction.

Learnability vs Efficiency in User Interface Design

"Summary: A "card" is a UI design pattern that groups related information in a flexible-size container visually resembling a playing card." Thus, a card can be defined as "a container for a few short, related pieces of information. It roughly resembles a playing card in size and shape, and is intended as a linked, short representation of a conceptual unit. A lot of high-profile sites such as Google (Material Design), Pinterest, or Twitter use cards."

Cards: UI-Component Definition

Design elements that appear similar in some way—such as sharing the same color, shape, or size—are perceived as related, while elements that appear dissimilar are perceived as belonging to separate groups.

Similarity Principle in Visual Design

"Summary: The more engaged users are, the more features an application can sustain. But most users have low commitment -- especially to websites, which must focus on simplicity over feature richness."

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