Towards rule-based visual programming of generic visual systems

This paper illustrates how the diagram programming language DiaPlan can be used to program visual systems. DiaPlan is a visual rule-based language that is founded on the computational model of graph transformation. The language supports object-oriented programming since its graphs are hierarchically structured. Typing allows the shape of these graphs to be specified recursively in order to increase program security. Thanks to its genericity, DiaPlan allows to implement systems that represent and manipulate data in arbitrary diagram notations. The environment for the language exploits the diagram editor generator DiaGen for providing genericity, and for implementing its user interface and type checker.Comment: 15 pages, 16 figures contribution to the First International Workshop on Rule-Based Programming (RULE'2000), September 19, 2000, Montreal, Canad

Graph Rewriting with Contextual Refinement

In the standard theory of graph transformation, a rule modifies only subgraphs of constant size and fixed shape.  The rules supported by the graph-rewriting tool GrGen are far more expressive: they may modify subgraphs of unbounded size and variable shape. Therefore properties like termination and confluence cannot be analyzed as for the standard case. In order to lift such results, we formalize the outstanding feature of GrGen rules by using plain rules on two levels: schemata} are rules with variables; they are refined with meta-rules, which are based on contextual hyperedge replacement, before they are used for rewriting.We show that every rule based on single pushouts, on neighborhood-controlled embedding, or on variable substitution can be modeled by a schema with appropriate meta-rules. It turns out that the question whether schemata may have overlapping refinements is not decidable

More on Graph Rewriting With Contextual Refinement

In GRGEN , a graph rewrite generator tool, rules have the outstandingfeature that variables in their pattern and replacement graphs may be refined withmeta-rules based on contextual hyperedge replacement grammars. A refined rule maydelete, copy, and transform subgraphs of unbounded size and of variable shape. Inthis paper, we show that rules with contextual refinement can be transformed to stan-dard graph rewrite rules that perform the refinement incrementally, and are appliedaccording to a strategy called residual rewriting. With this transformation, it is possi-ble to state precisely whether refinements can be determined in finitely many steps ornot, and whether refinements are unique for every form of refined pattern or not

Defining Models - Meta Models versus Graph Grammars

The precise specification of software models is a major concern in model-driven design of object-oriented software. Metamodelling and graph grammars are apparent choices for such specifications. Metamodelling has several advantages: it is easy to use, and provides procedures that check automatically whether a model is valid or not. However, it is less suited for proving properties of models, or for generating large sets of example models. Graph grammars, in contrast, offer a natural procedure - the derivation process - for generating example models, and they support proofs because they define a graph language inductively. However, not all graph grammars that allow to specify practically relevant models are easily parseable. In this paper, we propose contextual star grammars as a graph grammar approach that allows for simple parsing and that is powerful enough for specifying non-trivial software models. This is demonstrated by defining program graphs, a language-independent model of object-oriented programs, with a focus on shape (static structure) rather than behavior

Generating Instance Graphs from Class Diagrams with Adaptive Star Grammars

In model-driven software engineering, class diagrams are used to define the structure of object-oriented software and valid object configurations, i.e., what objects may occur in a program and how they are related. Object configurations are essentially graphs, so that class diagrams define graph languages. Class diagrams are declarative, i.e., it is quite easy to check whether a graph is an instance of a class diagram. Graph grammars, on the other hand, define a graph language by derivation and are thus well suited for constructing instance graphs. This paper describes how a class diagram can be translated into a graph grammar that defines the same graph language as the original class diagram. Such a graph grammar may then be used for, e.g., automatically generating valid object configurations as test cases. In contrast to earlier attempts, the presented approach allows to translate class diagrams with arbitrary multiplicities, unique and non-unique associations, composition associations, class generalization, association subsetting and redefinition. This is made possible by using adaptive star grammars, a special kind of graph grammars

Identifying business opportunities for green innovations: A quantitative foundation for accelerated micro-fuel cell diffusion in residential buildings

Combined heat and power (CHP) production in buildings is one of the mitigation options available for achieving a considerable decrease in GHG emissions. Micro-CHP (mCHP) fuel cells are capable of cogenerating electricity and heat very efficiently on a decentralised basis. Although they offer clear environmental benefits and have the potential to create a systemic change in energy provision, the diffusion of mCHP fuel cells is rather slow. There are numerous potential drivers for the successful diffusion of fuel cell cogeneration units, but key economic actors are often unaware of them. This paper presents the results of a comprehensive analysis of barriers, drivers and business opportunities surrounding micro-CHP fuel-cell units (up to 5 kWel) in the German building market. Business opportunities have been identified based not only on quantitative data for drivers and barriers, but also on discussions with relevant stakeholders such as housing associations, which are key institutional demand-side actors. These business opportunities include fuel cell contracting as well as the development of a large lighthouse project to demonstrate the climate-neutral, efficient use of fuel cells in the residential building sector. The next step could involve the examination and development of more detailed options and business models. The approach and methods used in the survey may be applied on a larger scale and in other sectors