With DICTEE it is possible to model specifications and generate code from these for all possible PLC platforms. DICTEE was developed by Strypes to develop software based on the National Tunnel Standard. From the specifications, software can be generated for any platform with minimal effort.
Challenges in the world of infrastructure
In recent years, models have become indispensable in the world of infrastructure. For example, it is nowadays customary to model complete structures in BIM (building information models) long before their realisation, requirements are recorded in tree structures using software such as Relatics and for technical installations Computational Fluid Dynamics (CFDs) are used to design systems such as ventilation and overpressure.
In the field of dynamic behaviour, modelling techniques such as SysML and tools such as Enterprise Architect are used to capture designs. Although the level of knowledge of both client and contractor is steadily increasing, there are still a number of challenges within the domain:
- Designs are out of plan;
- During the test phase, many findings are still being made in terms of requirements and design;
- Frictions may arise during the transition from detailed design (DO) to implementation design (UO) if it appears that certain design choices cannot be realised in practice.
These challenges have a number of causes:
- Although designs are recorded in SysML, a conversion to textual requirements still takes place;
- During the UO phase, designs are made “by hand”, as well as the underlying code and test documentation. Changes that occur during this process mean that documents and/or models must be adapted. This is intensive, and therefore error-prone, and a challenge to maintain traceability and demonstrability;
- There is often still a gap between the client’s wishes and the contractor’s expertise, as a result of which non-functional requirements can sometimes be lost during the design process.
The idea behind SysML is precisely to make it easier to discuss the design, determine the impact of changes and then implement them consistently. In this respect, there are still sufficient opportunities to derive added value from models.
Model Driven Engineering and the National Tunnel Standard (LTS)
Model Driven Engineering (MDE) dates back to the 1980s, as did the first CASE (Computer Aided Software Engineering) tools. This form of engineering sees the model as the source of all the information needed to realise a solution and always aims to improve productivity through re-use (of standardised models), simplify the design process and improve communication between individuals and teams. The chosen MDE approach is considered successful if the model is logical for people within the domain and if it is usable for further realisation.
For several years now, Rijkswaterstaat has been using the Dutch Tunnel Standard (Landelijke Standaard Tunnels, LTS), which applies to all new and renovated tunnels that meet the criteria of the standard. The aim of the standard is to provide a uniform and reusable set of specifications that can be applied to all tunnels, a concept that is certainly interesting from an MDE point of view.
Strypes took the initiative to investigate the feasibility of an MDE environment for the LTS and as a result realised the tool DICTEE.
The concept behind DICTEE
DICTEE is an application developed entirely within Strypes in order to quickly and easily realise platform-independent tunnel control based on the LTS concept. The development is based on two simple objectives:
- The environment must be usable for every employee who has knowledge of the LTS;
- The environment shall be able to generate the software of a complete tunnel-specific tunnel control system – without any human intervention – and then install it on any PLC.
The name “DICTEE” can be interpreted in two ways. First of all, the abbreviation stands for “Device Independent Code for Tunnels based on the Eclipse Ecosystem”, and it is also a metaphor for the traditional primary school dictation: the teacher dictates and the pupils take over, just as the LTS is literally dictated and adopted.
DICTEE’s design consists of a number of pillars:
- Recording composition – a model always starts with a composition of elements. In the case of the LTS, these are building blocks in the form of coordinating functions, basic functions, sub-functions and logical function fillers (LFFs). Such a building block is a combination of interfaces, behaviour and configuration. In addition to the LTS, it is possible to create a composition of components; for example, a row of escape doors of a traffic tunnel.
- Recording behaviour – The LTS describes the behaviour of some of the components.
The way of defining behaviour has been adopted in the tool.
- Possibilities for project-specific configuration – The LTS describes a standard tunnel, which in practice is often extended with functionality specific to the tunnel in question. It does contain the same installations, but the numbers often vary from tunnel to tunnel. The tool facilitates this by providing a project-specific configuration in addition to the definition of a standard tunnel. The standard tunnel provides validated “building blocks” where the configuration defines the actual numbers. In the generation process, building blocks are combined with the configuration to create a project-specific control system.
- Projections – People are visually oriented, which means that there will regularly be a need to display a model graphically so that, for example, it can be discussed more easily. For this purpose, the tool provides real-time projections of the textual model. These projections also form the basis for the generation of the design documents.
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