Sketches and diagrams play an important role in the daily work of software developers. In this paper, we investigate the use of sketches and diagrams in software engineering practice. To this end, we used both quantitative and qualitative methods. We present the results of an exploratory study in three companies and an online survey with 394 participants. Our participants included software developers, software architects, project managers, consultants, as well as researchers. They worked in different countries and on projects from a wide range of application areas. Most questions in the survey were related to the last sketch or diagram that the participants had created. Contrary to our expectations and previous work, the majority of sketches and diagrams contained at least some UML elements. However, most of them were informal. The most common purposes for creating sketches and diagrams were designing, explaining, and understanding, but analyzing requirements was also named often. More than half of the sketches and diagrams were created on analog media like paper or whiteboards and have been revised after creation. Most of them were used for more than a week and were archived. We found that the majority of participants related their sketches to methods, classes, or packages, but not to source code artifacts with a lower level of abstraction.
Although new technology is widely used for detailed design and image manipulation, its use in the early stages of visual invention is much less common, one reason being that the denotation systems used in paper-and-pencil sketching assist creativity in ways that are poorly understood. Leonardo da Vinci advocated the use of untidy indeterminacies for working out composition, because he believed that they stimulated visual invention. Recent research in cognitive psychology suggests a mental-imagery model that expands Leonardo’s theory and provides evidence for cognitive mechanisms that clarify the function of familiar sketch attributes. Sketches may mediate mental translation between spatially depictive and structurally descriptive modes of visual representation. Evidence for a hybrid percept-image theory of ordinary paper sketching is briefly outlined. Some implications of this theory for the development of improved computer sketching systems are briefly discussed. Abstract This paper is a study on the importance of drawing (both formal drafting and informal sketching) during the process of mechanical design. Five hypotheses, focused on the types of drawings, their necessity in mechanical problem solving, and their relation to the external representation medium, are presented and supported. Support is through referenced studies in other domains and the results of protocol studies performed on five mechanical designers. Videotapes of all the marks-on-paper made by designers in representative sections of the design process were studied in detail for their type and purpose. The resulting data is supportive of the hypotheses. These results also give requirements for future computer aided design tools and graphics education, and goals for further studies. External representations such as diagrams, sketches, charts, graphs and scribbles on napkins play facilitatory roles in inference, problem-solving and understanding (e.g. [1],[2],[3],[4],[5],[6],[7],[8],[9]). How does the externality and visibility of representations facilitate inference and problem-solving? One benefit of external representations is on memory. They reduce working memory load by providing external tokens for the elements that must otherwise be kept in mind. This frees working memory to perform mental calculations on the elements rather than both keeping elements in mind and operating on them [2],[9]. External representations also serve as visuo-spatial retrieval cues for long term memory, evoking relevant information that might not otherwise be retrieved. Another benefit of external representations is to promote discovery and inference, both visuo-spatial and metaphorical. Perceptual judgements about size, distance, and direction are easily made from external representations (e.g.[4]). In a Venn diagram, set relations such as inclusion are abstractly mapped onto visuo-spatial diagrammatic features, enabling direct perceptual calculation. Visuospatial features such as proximity, connectivity, and alignment provide useful hints to selection of appropriate inference paths (e.g.[1],[6],[8]) and to proper understanding of the structure of a target system (e.g.[5]). Calculations requiring counting, sorting, or ordering are easily made by rearranging external spaces (e.g. [7]).  Sketches are produced in many domains to communicate with self or others. They are a kind of external representation serving as a cognitive tool to augment memory and information processing by relieving the mind of some of those burdens. Sketches schematize. They do not portray reality; rather they convey conceptions of reality. Sketches use elements and spatial relations on paper to represent elements and spatial or abstract relations in the domain of interest. They incorporate relevant information and omit irrelevant. As such, they reveal people’s conceptions of domains.. An analysis of sketches of routes, for example, reveals that they segment routes around action points, typically turns. Order of drawing reflects mental organization of the domain. From sketches, novices extract structural information about the spatial relations among elements. Experts are also able to extract functional information, information that must be inferred from rather than directly extracted from sketches. Introduction Drawing and sketching are activities all humans engage in, at some level or another, as of a very young age (if not deprived of the sense of sight). In developed societies, toddlers use drawing implements to make marks on paper. In less-developed societies, children and adults use sticks to draw on sand. Why do children draw? It seems that for a child, drawing is a form of play, with developmental benefits similar to those of both symbolic play and construction games (play typology instituted by Piaget and Inhelder). Most people acquire enough drawing skills during childhood to make graphic production an accessible strategy whenever pictorial representation is more effective than linguistic representation in communication and reasoning. For some communication and reasoning tasks, however, ordinary drawing skills are not sufficient, just as linguistic skills acquired during childhood are not necessarily adequate for sophisticated verbal and written expression tasks. A better command of language makes for better orators and reporters, and a better command of drawing skills makes for better illustrators and decorators. A special class of representational skill, linguistic or graphic, is the one needed for inventive purposes: this is the case of the poet, the visual artist, and the designer. The inventive process does not require wider skills: not necessarily a larger vocabulary or unlimited graphic techniques. Rather, what is required is an ability to use the representational act to reason with on the fly. Usually, this is a “front edge” process in which partial and rudimentary representations are produced, evaluated, transformed, modified, refined, and replaced by others if need be, until their maker is satisfied with the results. The unique thing about such processes is that, since they involve ill-structured problem-solving, it is not clear at the outset where the process is leading to, and what the end result might be. In this paper, it is our purpose to look at the way in which sketching assists in generating ideas and strengthening them by interpreting the “backtalk” of a sketch in progress, or one that has just been completed. We use a developmental axis to illustrate our claims. We start with children and show how they “read” new information off their sketches or drawings, and use it to define or refine the rationale for their representations. We then show how designers habitually practice a similar process in the early idea-generation phase of the design process. This study presents an experimental investigation dealing with the support value of sketching activity in the early stages of the design process. The main focus is the process of sketching, including the sketching activity and the simultaneous use of the produced sketches. Sketching has a positive impact on the quality of the designed solution and on the individual experience of the design process. The quality of the solution concepts increases from entirely mental design problem solving without external support over partly supported to completely supported problem solving. On the basis of a representative case, the procedure of sketching and the activities performed while generating a design solution are analysed. A continuous change between internal mental and external materializing activities can be seen in the design process.  