Getting Started

Introduction

This section describes the following steps that must be done in order to start working with Address Space Model Designer:

• Introduction to Address Space Model Designer
• Introduction to user interface
• Information about sample solution, that is added to Address Space Model Designer

Introduction to Address Space Model Designer

OPC Unified Architecture (UA) is the next generation of OPC. One of its biggest improvements is a powerful Address Space and Information Model. To make the designing of the Address Space Model easier, CAS introduced an Address Space Model Designer that is a powerful tool, which allows creating, displaying and editing of the OPC UA models that are compliant with the Address Space standard.

There is no doubt that information technology and process control engineering have to be integrated to benefit from macro optimization and synergy effect. The only question is how to do this.

Industrial process management requires information of two types: process data and metadata. Metadata is a favorite keyword of the IT community because it sounds more seriously than "data describing data". The same way as process data represents the process physical state, metadata describes the process itself and in OPC UA both are represented by the Address Space.

The Address Space is intended to support integration by building common discipline, i.e. semantics (a knowledge base) and vocabulary - finally a language good enough to convey information up and down between levels of competence. If the parties want to speak only, they do not need to know the languages they use. It makes a difference if we are going to talk to each other and then we say that we are making the communicating parties interoperable. In other words, it is not enough to hear (transfer data), we have to understand (interpret it). Without mutual understanding, the voice is only an unpleasant noise. Unfortunately, talking about the same we can use two different languages: colloquial and formal ones. An expert will say that the colloquial language is ambiguous and cannot be used to convey more important information, and therefore should be avoided – I agree. Beginners probably will complain that a very precise and knowledgeable incomprehensible sentence is only nonsense – I agree too. Therefore we need to find something in the middle or use both approaches simultaneously.

Address Space is a language because it provides alphabet, syntax, and semantics. The language is specific because it is to be used to describe a real-time process. It is also computer-centric because it allows systems to control industrial processes to exchange information. Unfortunately, building completely unmanned systems is still science-fiction today. In spite of the effort spent on teaching machines our native language, we are unable yet to have a chat with them. Therefore learning the Address Space now seems to be an inevitable process. It is inevitable, but a question arises for whom. Because it is to be used for systems integration, the process involves plant people working at one level (responsible for process control) and corporate people working at another level (responsible for process management). Additionally, both communities are waiting for software tools developed by IT vendors that expand the population speaking the Address Space native language. The good news is that it is not a spoken language, only writing ability is expected.

The last but not least question we have to address is if we need a new dedicated language to read for example a drum temperature – although it is just a simple number. Of course, the answer is no. But if at the same time we need to know that the process consists of two drums connected by a pipe and the temperature of the first one is closely coupled with the temperature of the other one, the answer becomes not so obvious. Recognizing also the fact that we have to deal with two kinds of information:

• Static, e.g. nominal temperature and permanent connection
• Dynamic, e.g. current temperature and configuration of valves, drums

It becomes clear that the Address Space concept has no competitors now and, therefore, we have no options in this respect. The only topic for further discussion is how to learn it. The bad news is that using Address Space terminology the same information can be expressed by an almost unlimited number of means. Additionally, as usual when learning languages including the native one, the process is continuous and we can only talk about improving the language knowledge because designing a model for a real-time process we must apply the best practice together with the syntax and semantics. In other words, to be able to write not only a simple email but also a popular novel we have to couple the learning with training processes.

The main challenge of the project Address Space Model Designer is to bring together: learning, training and designing. To meet our objectives, we have just released:

• Documentation as a help collection containing linked topics recommended as a starting point to understand, design, develop and implement the Unified Architecture Address Space
• Address Space Model Designer that is a user-friendly tool supporting all aspects of the model designing process
• Documentation containing information about the Address Space Model Designer tool

To make this tool as useful as possible, the definition of the created Address Space can be saved to the XML file compatible with the schema used by the UA Software Development Kit released by the OPC Foundation.

Using the proposed approach you can learn how to develop, design a model, save it as XML and explore the created Address Space in the Unified Architecture environment in a couple of hours.

The design, development and deployment of the OPC UA Information Model detailed description is covered by the document Information Models Development