FlexiSketch: Combining Free-Form Sketching with Lightweight Metamodeling

Abstract

Most software modeling tools only support predefined modeling languages. They are not flexible enough for creative requirements elicitation and early design sessions because their restricted vocabularies cannot cope with the diversity of emerging ideas. Therefore, software and requirements engineers frequently use physical media such as whiteboards and paper to sketch models and communicate ideas. The resulting model sketches, or photographs thereof, are not amenable for processing by software modeling tools because they are represented as image files. As such, they come without explicitly defined model syntax and semantics. Instead, modelers either ignore the sketches or extract important information from them later in the software engineering process, using this information to manually build semi-formal models from scratch. This manual re-creation can be time-consuming and error-prone, because sketches are often ambiguous. It is difficult to disambiguate them since contextual data is usually not stored within the sketches, and the original intentions behind them might no longer be known. In this thesis, we propose a new, flexible modeling approach that enables a more seamless, semi-automatic transition from sketches to models. Our tool-supported approach combines sketching with lightweight metamodeling in a single modeling environment. We support free-form sketching similar to whiteboards and paper. In addition, sketched elements are recognized as individual constructs. A simple modeling language can be defined by annotating the constructs with types and constraints. The software automatically infers a metamodel by analyzing the whole sketch and the user's annotations. Thus, our approach supports several levels of formality. It enables the transformation of sketches into models, and paves the way for exporting them to other modeling or metamodeling tools. This thesis presents the conceptual solution of our approach, the FlexiSketch tool as a proof of concept and embodiment of this approach, and an evaluation of the approach in the form of initial studies with students and practitioners. The study participants deemed our approach to be valuable and pointed out that the simplicity and flexibility of our tool make it much more suited for creative work than other software modeling tools. Overall, the studies show that our approach is a successful example of blending advantages of whiteboards and software modeling tools, in order to obtain a flexible modeling tool that enables a powerful integration of sketches into the software engineering process. Furthermore, the studies confirm an industry need for such flexible tools.