The following is an overview, analysis, and detailed breakdown of Lim, Stolterman, and Tenenberg’s paper, ‘The Anatomy of Prototypes’, which is available here.
Overview
The overall objective of this paper is to propose a ‘framework for prototype conceptualisation’ - which essentially means a way of classifying and identifying prototypes, in such a way that supports understanding of the fundamental characteristics of prototypes. Examples of prior taxonomies included ’low- vs. high-fidelity’ or ’experience vs paper’, but the authors claim that these fail to get at the fundamental essence of prototypes, and are less broadly applicable than their proposed anatomy.
The authors claim that their framework views the role of prototypes not only as tools for evaluation, but also as tools for exploring a design space, and reflecting on the design activities themselves. They further backup their claims stating that the framework is based on the findings of two case studies, which yielded ‘prototypes as filters’ and ‘prototypes as manifestations’ as the two key concepts for classifying prototypes.
The Introduction
‘Prototype’ is initially introduced as an object in the design process, that traditionally is viewed as a tool for evaluation of design failure or success. This view is countered, and the authors suggest that formal evaluation is only a small part of the roles that prototypes fill, stating that they are also:
the means by which designers organically and evolutionarily learn, discover, generate, and refine designs.
Current approaches in which prototypes are used to identify and satisfy requirements are deemed ‘requirement-oriented approaches’, and their key limitation is identified as the lack of applicability to flexible design approaches. The authors also perceptively note that :
A design idea that satisfies all the identified requirements does not guarantee that it is the best design since a number of ways can meet each requirement.
The authors then point out that if the purpose of the prototype is to explore a design space (which the authors will assume to be the case for the remainder of the paper), then identifying or meeting requirements is not important, but instead finding a prototype that filters the qualities the designers are interested in, without distorting the overall understanding. This is called the fundamental prototyping principle, a term defined by Wong in an earlier paper (1992). I suppose that this is to the end of gaining an intuitive understanding of that specific quality, and the quality of filtering refers to a prototype that is distilled sufficiently that the filtered-for quality is the main factor impacting the understanding gained from the prototype, but this is not fully explained at this stage.
The ultimate goal is given as a framework to allows designers to specify goals and questions when considering prototypes. The framework is based on two fundamental aspects of prototypes
- Prototypes are for traversing a design space
- Prototypes are implementations of design ideas
The concept of filters is then developed, and justified as appropriate for prototypes as they can screen out irrelevant aspects of designs. They further assume:
The decision of what to filter out is always based on the purpose of prototyping.
Next, ‘material, resolution, and scope of a prototype’ are given as parts of a manifested prototypes anatomy - and are henceforth referred to as manifestation dimensions. These dimensions are, for a given prototype, determined via the economic principle of prototyping, which itself is defined as
The best prototype is one that, in the simplest and most efficient way, makes the possibilities and limitations of a design idea visible and measurable.
Introduction Summary
So overall, the authors have claimed that:
Prototypes are manifestations of design ideas
Prototypes are not solely a tool for evaluation of design failure or success, or identifying met requirements (which they have commonly been viewed as being)
Instead they are filters that help explore a design space (fundamental prototyping principle)
The best prototype is the minimal one that make design idea possibilities and limitations measurable (economic principle of prototyping)
This is then sufficient to explain the paper’s full title: The anatomy of prototypes: Prototypes as filters, prototypes as manifestations of design ideas.
How Prototyping is Understood in Current Research in HCI
The authors state that previous discussions on prototyping largely focus on fidelity, particularly various types of low-fidelity prototypes, which are favoured due to cost. Various forms of low-fidelity prototypes are listed. They clarify that the notion of fidelity is useful, but a simple binary label of low-vs-high fidelity has shown to be problematic in some cases. Mixed-fidelity is highlighted as effective, since it combines low and high fidelity via having different dimensions of a design show different fidelities.
Prototyping for representing design ideas is also explored. ‘Sketching’ as a method for rapid concept externalisation is discussed, with prior work compared, due to its popularity in research.
Participatory design - that is, design approaches that involve end-users in the design process, is discussed, with the role of prototyping here being to actively engage the users, and design idea exploration.
The authors then state that these ideas, and many others, are used without a reflective understanding of how they differ from each other. A number of papers that have tried to evaluate each technique are highlighted, and multiple’s findings are discussed. They highlight Lichter et al.’s work, which attempts to summarise taxonomies of four types of prototypes in software development:
- Presentation prototype - demonstrates a design idea aspect for client-developer communication
- Prototype proper - describes aspects of design ideas for understanding and discovery of problems
- Breadboard - evaluates construction-related questions
- Pilot system - resembles final application for refinements
They then point out that this, and other existing taxonomies of prototypes are based on the different ways of using them, rather than on what they are.
Current prototyping research can best be described as an ongoing attempt to come up with what to do with prototypes without understanding what they actually are.
Prototypes as filters
This section largely elaborates on the idea that prototypes are incomplete, this is identified as their primary strength. This of course supports the idea that they can be viewed as filters of design ideas and qualities. An example use case of a camcorder is given, showing the ideal ergonomic quality filtering prototype, which is a simple foam shape, the interface and viewfinder which is a sketch, and the working input breadboard, which is a 3D form. The key detail is that prototypes are intricately intertwined with the evolution of design ideas throughout the design process.
Prototypes as Manifestations of Design Ideas
Iteration is highlighted as being key for the design process - specifically iterated interaction with external design manifestations (prototypes). Externalisation of thought is stressed as being integral to the process of cognition itself, the paper gets pretty deep at this point, with former work by Clark being quoted:
we are in the grip of a simple prejudice: the prejudice that whatever matters about MY mind must depend solely on what goes on inside my own biological skin-bag, inside the ancient fortress of skin and skull. But this fortress was meant to be breached
Deep. They’re essentially getting at the idea that externalization of thought gives rise to the potential for reflection, critique, and iteration. The authors posit that externalisation is, in fact, essential to creation itself. This is reiterated and explored in some detail, with the aim of claiming that manifesting design ideas and thoughts (prototyping), is inherent to design. Materials are briefly explored as having various properties and limitations that diverge the prototypes from the final design, and related to the more general concept of difference in scope of prototypes, which will be explored in more detail.
Anatomy of Prototypes
Finally! The authors present their framework for the anatomy of prototypes, basing this on the earlier two key concepts of ‘prototypes as filters’ and ‘prototypes as manifestations of design ideas’. The terms prototype, prototyping, and anatomy are explained.
The anatomy includes the following filtering dimensions:
| Dimension | Example Variables |
|---|---|
| Appearance | size, color, shape, margin, form, weight, texture, proportion, hardness, |
| Data | data size, data type, data use, privacy, |
| Functionality | system function, users’ functionality need |
| Interactivity | input behavior, output behavior, feedback behavior, information |
| Spatial Structure | arrangement of interface elements, relationship among interface or information elements |
Along with the following manifestation dimensions:
| Manifestation Dimension | Definition | Example Variables |
|---|---|---|
| Material | Medium (visible or invisible) used to form a prototype | Paper, wood, plastic; tools like scissors and pens; software like Flash; hardware like Phidgets; existing gadgets |
| Resolution | Level of detail or fidelity in the prototype | Performance accuracy; feedback speed; appearance and interactivity realism |
| Scope | Range or extent of what the prototype covers | Contextual depth, e.g., isolated color charts vs. full UI; partial vs. full navigation interface |
An example of mobile phone prototyping is used to demonstrate that having both filtering and manifestation dimensions is important, as the right manifestation dimensions should be selected to ensure that the filtered dimensions can be effectively explored.
Each of the dimensions is explained in detail, and it is highlighted that they are not meant to be complete, instead simply useful. The iPod is explored as interactivity is tied to its basic appearance. Its explained that the filtering dimensions provide the initial direction for prototype formation, but the manifestation dimensions guide the actual formation of the prototype. Its argued that the manifestation dimensions influence how well a prototype performs as an informing tool in the design process, with discussion at length.
Two Use Cases Explored
The authors now go on to demonstrate a use of the proposed anatomy, via a house design, and then a mobile phone prototyping application. The first case is used to show the effects of filtering dimensions, and the second for manifestation dimensions. Both examples build on prior studies of these cases.
For the house case, a 2D blueprint and a 3D virtual model were compared as prototype options. The blueprint primarily filtered spatial structure, meaning users focused on layout and relationships. The 3D model filtered appearance and interactivity, resulting in users commenting on aesthetics and having a feeling of “being” in the house. This shows that different prototypes implementing the same design resulted in very different understandings of the idea, since each filters for certain properties inherently. E.g. choosing the 3D models means that the colours of walls must be defined, where in a blueprint this is not necessary.
For the phone case, paper, computer-screen, and a fully functional phone, were all compared as prototypes. All 3 focused on filtering for the interactivity dimension, with very different manifestation dimensions. The study found that only a small percentage of usability findings were common across all three prototypes. This demonstrated how differences in manifestation dimensions change evaluation results. For example, with the paper prototype, the material didn’t enable users to push the buttons on the keypad area, which made registering these actions and updating the paper interface delayed, which negatively impacted overall experience of interaction - even though this flaw is only inherent to this particular manifestation.
Conclusion
At the end of the paper, the authors list 3 possible contributions of the work in interaction design:
- the anatomy framework provides a language that can be used to articulate any prototype.
- the anatomy framework of prototypes provides a critical thinking guide when designing and constructing prototypes.
- this framework can be used for constructing prototype profiles in real design practice that can help designers in producing quick-and-dirty prototyping plans before they construct prototypes.
The authors stress that they have shown that it is possible to identify and plan for prototype characteristics. They also state that by being aware of this anatomy, designers can approach the task of forming and using prototypes in a more intentional way. They stress that its important to understand that prototypes are different from the final form of a design, and that they significantly affect how manifested ideas are perceived. The broad purposes of prototypes are given:
- evaluation and testing
- the understanding of user experience, needs, and values
- idea generation
- communication among designers
Limitations?
Limitations are not really explored in the paper, and as the paper presents fairly abstract concepts and ways of thinking about prototypes, there are fewer limitations than other papers. The authors do however stress that:
It is, however, true that the framework we propose here is not an absolute one.
And previously acknowledge that the descriptions they provide are not complete. They address this concern with the following statement:
We do not propose this framework as a prescriptive approach for the design of prototypes in interaction design. But, designers can learn from the framework and can let the framework and earlier experiences inform their decisions in a specific design situation.
Final Thoughts
This paper provides a very deep dive into prototyping, and gives a more academically formal way of understanding and discussing prototypes. The language of filtering dimensions and manifestation dimensions are useful overall, and makes properties that are often only implicitly recognised clearer. Direct consideration of these factors may encourage thought about how best to create a prototype, in order to gain understanding of specific aspect of a design. This is a largely useful contribution.
The paper is very long, and could possibly have been condensed, with frequent repetition of the key concepts that the authors implement. Reading is not aided by the single column format, and lack of images or diagrams. As this is a discussion and taxonomy-focused work, this is understandable, and the abstract and conclusion do effectively highlight key-takeaways.
Discussion in section 4: Prototypes as manifestation of design ideas is particularly deep, and provides interesting insight into the creative and design processes.