A Comparison of the Declarative Modelling Languages B, Dash, and TLA+

Abstract

Declarative behavioural modelling is a powerful modelling paradigm that enables users to model system functionality abstractly and concisely. We compare two well-used formal declarative modelling languages, B and TLA + , with a new modelling language called Dash. Dash is an extension of Alloy with explicit syntactic constructs for modelling transition systems, and it includes control state hierarchy and events. Particular topics that we cover in our comparison are: differences in the datatypes and type systems; how the transitions/operations can be described; how the transition relation is a combination of the transitions; and the default choice each language makes regarding permitted variable changes in a transition. Our goal is to discuss the interesting differentiating characteristics of each language to aid users in determining which language is the most suitable for their system.

A Comprehensive Study of Declarative Behavioural Modelling Languages

“…To qualitatively compare declarative modelling languages for writing a model of a transition system, we began by selecting six relatively small examples and modelled them in three declarative modelling languages (B, DASH, and TLA + ), forming an initial set of comparison criteria for the languages and publishing our initial results [16].…”

“…We then used that first version as the reference model for the other models of that case study in different languages. Our first three models of EHealth, digital watch, and musical chairs were completed concurrently (in our original study [16]), and thus are all labelled '1' in the table. For the case studies where no reference model was available, we used the informal or semi-formal description of the system from the originating paper to write a first model, and used that model as our reference for the subsequent models of the case study.…”

“…In B and EVENT-B, type signatures are declared in the INVARIANT section along with other invariants (e.g., lines [15][16][17][18][19][20][21][22][23]. B and EVENT-B use typechecking to statically catch type errors like assigning a value from a set to a variable with a type signature declaring a different/incompatible set, and applying a function to an argument not matching its type signature (prior to model checking).…”

TLA+ model checking made symbolic

“…We briefly compare TLA + tools with Alloy and B. More detailed comparisons can be found in [Abbassi et al 2018;Newcombe 2014]. Table 7 summarizes the comparison between these languages.…”