Mark Minas

Concepts and realization of a diagram editor generator based on hypergraph transformation

Diagram editors which are tailored to a specific diagram language typically support either syntax-directed editing or free-hand editing, i.e., the user is either restricted to a collection of predefined editing operations, or he is not restricted at all, but misses the convenience of such complex editing operations. This paper describes DIAGEN, a rapid prototyping tool for creating diagram editors which support both modes in order to get their combined advantages. Created editors use hypergraphs as an internal diagram model and hypergraph parsers for syntactic analysis whereas syntax-directed editing is realized by programmed hypergraph transformation of these internal hypergraphs. This approach has proven to be powerful and general in the sense that it supports quick prototyping of diagram editors and does not restrict the class of diagram languages which it can be applied to.

DiaGen: a generator for diagram editors providing direct manipulation and execution of diagrams

Diagrams (e.g., flowcharts, trees for hierarchical structures, or graphs for finite state machines) are often needed as part of visual language systems and advanced user interfaces, and are frequently application specific. The implementation of editors for diagrams should be supported by a tool and based on a formal model. This paper gives an overview of DiaGen, a generator for diagram editors. An editor for a certain kind of diagram is generated from a specification, which includes a hypergraph grammar to describe the structure of diagrams. The user of a diagram editor does not have to be concerned with the grammar, but can manipulate diagrams very conveniently by direct manipulation. As an additional and important feature in the context of visual languages, editors generated by DiaGen cannot only be used for editing, but also for executing, i.e., animating diagrams.

Diagram editing with hypergraph parser support

Diagrams are always used when communicating complex situations. Diagram editors support the user when editing diagrams on a computer. However creating diagram editors is expensive and time consuming. Frameworks that can be customized for the specific diagram classes considerably reduce these costs. In previous work, the framework DiaGen using an internal hypergraph model and offering syntax directed editing had been introduced. The paper presents an incremental hypergraph parser and an extension of DiaGen that allows for editing diagrams like in a drawing tool. The hypergraph parser detects correct (sub) diagrams online and notifies the user of incorrect diagram parts. This allows editing with temporally inconsistent diagrams which supports a natural editing style.

Generating Meta-Model-Based Freehand Editors

Most visual languages as of today (e.g., UML) are specified using a model in a meta-model-based approach. Editors for such languages have supported structured editing as the only editing mode so far. Free-hand editing that leaves the user more freedom during editing was not supported by any editor or editor framework since parsing has not yet been considered for meta-model-based specifications. This paper describes the diagram editor generator framework DiaMeta that makes use of meta-model-based language specifications and supports free-hand as well as structured editing. For analyzing freely drawn diagrams, DiaMeta parses a graph representation of the diagram by solving a constraint satisfaction problem.

PLC programming with signal interpreted Petri nets

In this paper a graphical editor to design Programmable Logic Controller (PLC) programs using Signal Interpreted Petri Nets (SIPN) is presented. SIPN are an extension of condition event Petri nets that allow the handling of input and output signals. The presented tool, SIPN Editor, has been developed using DiaGen which is an environment for rapidly developing diagram editors from a formal specification of the diagram language. The SIPN Editor supports the translation of SIPN into input code for the model checker SMV. Using SMV, the SIPN can be verified before it is automatically translated into Instruction List code according to the IEC 61131-3 standard. This code can be downloaded on nearly every PLC.

Visual PLC-programming using signal interpreted Petri nets

In this contribution, we present a graphical programming approach for Programmable Logic Controllers (PLCs) based on a special type of Petri net, the Signal Interpreted Petri Net (SIPN). We give an introduction to PLCs and an overview of the languages used to program them. From this overview, we conclude that for PLCs a language is missing that is capable of a simple graphical description of sequential and concurrent behavior. SIPN is such a language. We present the SIPN approach and some corresponding analysis methods. Furthermore, we report on some experiments done in a university course, that show that the method is indeed useful in solving control problems. Since programming a controller without tool-support is nearly impossible, we present a tool for graphical editing and compilation of SIPN. In the development of the tool, not only the implementation of the SIPN as it is defined in theory played a role, but the projected application area and user interest were also considered.

Adaptive star grammars

We propose an extension of node and hyperedge replacement grammars, called adaptive star grammars, and study their basic properties. A rule in an adaptive star grammar is actually a rule schema which, via the so-called cloning operation, yields a potentially infinite number of concrete rules. Adaptive star grammars are motivated by application areas such as modeling and refactoring object-oriented programs. We prove that cloning can be applied lazily. Unrestricted adaptive star grammars are shown to be capable of generating every type-0 string language. However, we identify a reasonably large subclass for which the membership problem is decidable.

Business Process Models as a Showcase for Syntax-Based Assistance in Diagram Editors

Recently, a generic approach for syntax-based user assistance in diagram editors has been proposed that requires the syntax of the visual language to be defined by a graph grammar. The present paper describes how this approach can be applied to the language of business process models (BPMs), which is widely used nowadays. The resulting BPM editor provides the following assistance features: combination or completion of BPM fragments, generation of BPM examples, an extensive set of correctness-preserving editing operations for BPMs, and auto-link, i.e., the automatic connection of activities by sequence flow. Furthermore, this paper contains a discussion of the scalability and scope of the used approach. This also comprises a characterization of the languages where it can be put to a good use.

Auto-completion for diagram editors based on graph grammars

Graphs are known to be well-suited as an intermediate data structure in diagram editors. The syntax of a particular visual language can be defined by means of a graph grammar. In recent work we have proposed approaches to graph completion: given a possibly ldquoincompleterdquo graph, this graph is modified in such a way that the resulting graph is a member of the grammarpsilas language. In this paper we describe how graph completion can be used to realize diagram completion, an important requirement for the realization of content assist in diagram editors. With our approach, the advantages of free-hand and structured editing can be effectively combined: drawing of diagrams with maximal freedom and powerful guidance whenever needed.

Hypergraphs as a Uniform Diagram Representation Model

When working with diagrams in visual environments like graphical diagram editors, diagrams have to be represented by an internal model. Graphs and hypergraphs are well-known concepts for such internal models. This paper shows how hypergraphs can be uniformly used for a wide range of different diagram types where hyperedges are used to represent diagram components as well as spatial relationships between components. This paper also proposes a procedure for translating diagrams into their hypergraph model, i.e., a graphical scanner, and a procedure to check the hypergraph against a hypergraph grammar defining the diagrams’ syntax, i.e., a parsing procedure. Such procedures are necessary to make use of such a hypergraph model in visual environments that support free-hand editing where the user can modify diagrams arbitrarily.