Specification

Having identified the needs of the customers and other stakeholders, the product specification enables these needs to be agreed and communicated within the design team. The specification provides a link between the language of the customer and the language of the business and in particular, the language of the engineer.

A product specification should provide precise, measurable and unambiguous detail about what the product must do, without providing unnecessary constraints or suggesting possible solutions. As a critical document in the design process, it should represent unambiguous team agreement.

The design brief vs the product specification
The design brief describes what the product must be. It outlines the objectives, goals and functions of the required product and does not normally have precise limits; it describes the required product. The brief outlines the product aims, which should be as specific as possible, without indicating solutions or limiting the scope of possible solutions.

In contrast, the product specification defines the required performance of the required product outlined in the brief. The product specification limits the range of acceptable solutions and sets boundaries to the solution space, which later provide a baseline for the evaluation of solutions. The specification aims to provide precise limits to individual parameters, distinguishing between wishes and needs, from both the company's and the users' perspectives.

Thus, the design brief is not the same as a product specification, but is certainly closely related. Ideally, the design brief is a starting point from which the unknown aspects of the product and market can be identified, researched and defined.

Having identified the needs of the customers and other stakeholders, the product specification enables these needs to be agreed and communicated within the design team. The specification provides a link between the language of the customer and the language of the business and in particular, the language of the engineer.

A product specification should provide precise, measurable and unambiguous detail about what the product must do, without providing unnecessary constraints or suggesting possible solutions. As a critical document in the design process, it should represent unambiguous team agreement.

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It has been demonstrated that the ability of someone to read a brief is inversely proportional to the length of the brief! Thus, it is a good discipline to summarise the project objectives, goals and benefits on a single sheet, along with an indication of the intended role of the industrial designer, maybe following the same major headings as the more detailed brief:

• The opportunity
• The proposed product
• The project
• The Industrial design requirement

Using visual media and analogies
Several elements of the brief do not lend them selves to written communication. When describing the intangible aspects, it is often most effective to use imagery, analogy and visual means. Traditionally, designers have used images to build 'mood' or 'style' boards, which help support and focus the creative process. Such tools are an excellent way of developing team agreement and understanding over ergonomic and aesthetic issues. Such image boards should be at least A2 size and use images from brochures, professional publications, journals, magazines or the web. Before a session, some preparation is needed to collect together suitable publications. Some examples of how image boards might be used are given below:

• To describe the customer
  Images of typical customers, preferably operating in their typical environments. This could be built as a single board, representing the range of potential users, demonstrating their diversity. Alternatively, individual users could be 'caricatured' to show the nature of a typical user. It can also be informative to produce an image board which shows unrelated products which may be used by the target customer group, to highlight any specific stylistic, material or visual trends. This helps to indicate the importance of fashion, style and image to the target audience and more importantly, indicates the types of 'visual values' which are seen as important to them.

• To describe competitive products
  Rather than a table, listing product specifications and ranking the competitors for performance, aesthetics and ergonomics, it can be informative to see images of competitive products side by side.

• To describe the place of use
  Again, rather than 'describe' the place of use, use images to indicate the typical locations in which the product is likely to be used. Again, as with the customer, this could either demonstrate the diversity of possible locations or caricature the most likely ones. It can also be useful to produce an image board which includes products which are typically seen in similar environments. This can give visual cues to some of the stylistic features and trends seen in other products.

• To describe the means of use
  It can be informative to collect images of products which are used in similar ways. If the product is to be 'hand held', collect images of 'hand held' devices to provide insight into the different ways in which this could be achieved.

• To describe the visual values desired
  'Mood boards' are traditionally used by designers to convey the mood or feel of the product and involve the collection of images which suggest the look, feel, texture, atmosphere etc. These images tend to be more abstract and suggestive. However, similar approaches can be taken to demonstrate 'lifestyle', or more simply just 'style'

Who should produce it?
The product specification should unite the whole design team, regardless of their functional orientation, around the requirements of the product and how those requirements are related to underlying customer needs. Thus, the generation of the specification is a team responsibility. It is undesirable to produce separate 'marketing' and 'technical' specifications, as this can reinforce functional divisions, create a focus for disagreement and is sometimes a get-out from the difficulty of trying to understand the different perspectives.

How should the specification be used?
Typically, the specification is generated as an input to a stage review or project gate meeting. From this point, it becomes the control document against which design decisions are evaluated. In a long development programme, the specification may stay the same, whilst the needs of the market place have progressed. The product specification provides a tool to guide the design team, but not the ultimate benchmark by which the final solution should be judged. The only realistic benchmark is the customers themselves.

Not just a wish list
The specification should not be an uncorroborated 'wish list' generated by the marketing department to be as challenging as possible, with the justification that "if we get half of what we ask for, then it might just be alright." Nor should the specification be a list of 'what we can achieve' in order to make the life of the engineers a little bit easier. The specification should be based primarily on 'what do users need'. To support this, it is useful to think both in terms of "must have", "need" and "want" as a simple way of classifying requirements. Alternatively, requirements can be viewed from the users perspective:

• "basic attributes" - these are fundamental and must be present
• "linear attributes" - customer delight will increases with improved levels of execution
• "exciter/delighter attributes" - surprising features, for which the customer may pay a premium

The design mix
The product specification is often viewed as an 'engineering document'. Indeed, it is frequently called the 'technical specification' or 'engineering requirements'. An engineering biased view can create barriers between customer facing and technical disciplines. The specification becomes a description of the 'tangible' engineering characteristics which are quantifiable and measurable.

A more serious consequence of an overly technical orientation is that aspects relating to how, where, why and who the product will be used by are often overlooked. These 'intangible' elements of the design mix can be difficult to quantify, specify and measure - but it does not mean you shouldn't try. It can be more effective to consider the representation of form, appearance, style, usability and feel using visual means. Simple 'mood boards' or 'concept boards' can provide more information than several pages of text describing the market.

Good v Bad specifications

Further information

• Bruce M, Cooper R, (2000), Creative product design: a practical guide to requirements capture management, John Wiley & Sons, UK
• Otto & Wood, (2000), Product design, Prentice Hall
• Pugh S, (1996), Creating innovative products using total design: the living legacy of Stuart Pugh, Addison-Wesley Publishing Company, USA
• Reinertsen, (1997), Managing the design factory, Simon & Schuster
• Ulrich & Eppinger, (2000), Product design and development, McGraw Hill, USA

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