When software engineers collaborate, they frequently use whiteboards or paper for sketching diagrams. This is fast and flexible, but the resulting diagrams cannot be interpreted by software modeling tools. We present FLEXISKETCH TEAM, a tool solution consisting of a significantly extended version of our previous, single-user FLEXISKETCH tool for Android devices and a new desktop tool. Our solution for collaborative, model-based sketching of free-form diagrams allows users to define and re-use diagramming notations on the fly. Several users can work simultaneously on the same model sketch with multiple tablets. The desktop tool provides a shared view of the drawing canvas which can be projected onto an electronic whiteboard. Preliminary results from an exploratory study show that our tool motivates meeting participants to actively take part in sketching as well as defining ad-hoc notations.

Whiteboards and paper allow for any kind of notations and are easy to use. Requirements engineers love to use them in creative requirements elicitation and design sessions. However, the resulting diagram sketches cannot be interpreted by software modeling tools. We have developed FlexiSketch as an alternative to whiteboards in previous work. It is a mobile tool for model-based sketching of free-form diagrams that allows the definition and re-use of diagramming notations on the fly. The latest version of the tool, called FlexiSketch Team, supports collaboration with multiple tablets and an electronic whiteboard, such that several users can work simultaneously on the same model sketch. In this paper we present an exploratory study about how novice and experienced engineers sketch and define ad-hoc notations collaboratively in early requirements elicitation sessions when supported by our tool. Results show that participants incrementally build notations by defining language constructs the first time they use them. Participants considered the option to re-use defined constructs to be a big motivational factor for providing type definitions. They found our approach useful for longer sketching sessions and situations where sketches are re-used later on.

Traditionally, metamodeling is an upfront activity performed by experts for defining modeling languages. Modeling tools then typically restrict modelers to using only constructs defined in the metamodel. This is inappropriate when users want to sketch graphical models without any restrictions and only later assign meanings to the sketched elements. Upfront metamodeling also complicates the creation of domain-specific languages, as it requires experts with both domain and metamodeling expertise. In this paper we present a new approach that supports modelers in creating metamodels for diagrams they have sketched or are currently sketching. Metamodels are defined in a semi-automatic, interactive way by annotating diagram elements and automated model analysis. Our approach requires no metamodeling expertise and supports the co-evolution of models and meta-models.

Early stage requirements models are often documented using paper and pencil-based approaches. In our current research, we are exploring lightweight modeling tools and approaches that could provide a beneficial alternative. We have developed the FlexiSketch tool prototype which combines support for free-form sketching with lightweight metamodeling capabilities. This creates the possibility for an automatic transcription of the documented information in later modeling stages. The tool is designed to be used on tablet devices.