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RTA Dictionary

Too many Rt's around? That's how it should be in a real-time environment.

Here you find short technical descriptions of all the Rt* components that constitute RTA:

RtDb - Real Time Database

a network-wide, distributed, active, real-time database that provides high speed data distribution via the TCP/IP network. In contrast to conventional real-time capable database systems, RtDB represents a combination of an active, real-time and a relational database. Thus RtDB provides on the one hand an interface to the active, real-time database for high-speed data processing and a SQL interface to the relational database for standardized data access. The integrity of the data between the real-time database and the relational database is assured by a synchronization mechanism, which automatically keeps track of changes in either of the databases. It provides for distribution of changed data between the two databases as well as providing for distribution of data changes between different nodes in a distributed or redundant system. RtDB uses RtIpC to distribute data to other nodes. Thus real-time database tables can be distributed in a network.
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RtIpC - Real Time Interprocess Communication

a network-wide inter-process communication mechanism (queue based) that allows high data transmission rates between applications. Data transmission can be done between applications within single nodes as well as between applications on different nodes in a network (TCP/IP). On local nodes shared memory is used which makes the communication very fast. It also incorporates RtRM which enables it to selectively communicate with applications on e.g. the MASTER node or STANDBY node only.
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RtRM - Real Time Redundancy Manager

a supervisor function that has network-wide control over RTA nodes and RTA applications in redundant systems to allow real-time MASTER - STANDBY switching (software switching) in case of system malfunctions. The real time redundancy manager is not only required for the implementation of redundant configurations, it has also control over all important applications on single nodes. Its job is to watch over all RTA components and applications and, in case a component or program fails, to activate specific routines like system restart or node switching (MASTER-STANDBY switching).
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RtVar - Real Time Variables

RtVars are Real Time Variables that can be accessed using RtPL as well as Visual Studio program languages (like Visual Basic, Visual-C). RtVars provide access to all necessary components in the system like RtDB tables, Oracle tables, operating system information (environment, timers etc.). An RtVar can be active or passive. Active RtVars allow external triggers to be activated whenever the value of the RtVar changes. Due to that a system based on RTA is very much event-driven. At the first glimpse Real Time Variables (RtVars) look like and behave like normal variables in BASIC or C programs and as such they are very simple to handle. But compared to regular variables RtVars provide some tremendous advantages:

  • Events: whenever the value of a RtVar is changed the RtVar generates an event, programs can install triggers to catch such events and immediately launch specific processing depending on the new value of the changed RtVar
  • Complex Data Types: beside the elementary data types like INTEGER, STRING, DOUBLE, ADDRESS (for pointer usage) and BINARY (for blobs) RtVars implement a wide range of complex data types. Complex data types provide access to a big number of different data sources (read access) and data destinations (write access) in a very simple way. Hence access to the operating system date and time functions, to operation system environment variables, to SQL database tables and many other data sources and destinations, is established through RtVars in quite the same simple way like e.g. for an INTEGER or for a STRING RtVar.
  • Extended Scope: an elementary RtVar can have a LOCAL scope (it is known in the local procedure), a MODULE scope (it is known in a certain module), a GLOBAL scope (it is known in the current task/program), a COMMON scope (it is known on the current node/computer) or a NETWORK scope (it is known on all nodes/computers in the network). The scope of a Complex RtVar depends on the type of the RtVar, e.g. a date/time RtVar has a COMMON scope because the system date and time provided by the operating system is valid for the whole node/computer.
  • C-API: this allows C programs to make full use of all RtVar features via an API. Although existing RtVars can be defined and used via this API, the main purpose of this API is to allow for the implementation of additional RtVar types (new complex data types). Such a new RtVar type could e.g. be a graphical object with all its attributes. In case of a graphical input object the RtVar may be readable and write-able (source and destination), in all other cases it may only be write-able (destination) to allow changes on the attributes of the graph.
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RtPL - Real Time Program Language

Is a BASIC like programming language that was primarily developed to take full advantage of RtVars in a simple and efficient way. RtPL programs are simple ASCII files that are automatically 'compiled' into memory at load time. No separate compiling and linking is necessary. Although RtPL files are plain ASCII files, the fact that they are 'compiled' into memory makes them extremely fast. The fact that they are just ASCII files that don't require compilation and linking, makes them most suitable for Rapid Application Development and Prototyping. RtPL files are used for implementation of the core of real-time process control applications. The RtPL language provides constructors to implement loops and conditions and to define and use RtPL functions and procedures and, most off all, to use RtVars. The Real Time Application Programming Language (RtPL) provides a mechanism to specify ECA Rules (Event Condition Action Rules) using RtVars. The condition is specified as RtVar expression which is triggered whenever e.g. the value of the RtVar changes. If the condition is met the action is executed. The action may be any C or RtPL function or procedure or just a plain PL statement. ECA Rules extend the functionality of RtPL far beyond the functionality of most existing programming languages.
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