TTCN-3 Core Language is the textual presentation format to specify test suites, including BNF syntax and operational semantics. An available editor for TTCN-3 Core Language is the CL Editor integrated in Testing Technologies' TTworkbench.
The Tabular Presentation Format, taken from concepts out of TTCN-2, is another way to describe TTCN-3 test behavior tabularly.
The graphical presentation format of TTCN-3 (GFT) is based on the ITU-T Recommendation Z.120  defining Message Sequence Charts (MSC). The GFT eases and speeds up test suite design and in parallel creates an appealing documentation. One of the leading graphical editors is the GFT Editor of Testing Technologies.
This part of the TTCN-3 standard describes the semantic, meaning and definition of functions, data, types and templates etc.
TRI is the Runtime Interface in the concept and standard of TTCN-3 being responsible for the implementation of specified test suites. It describes and defines the communication interfaces between Test Suite and System Under Test specified in the System Adapter (SA). It also includes a Platform Adapter to have access to external functions and integration of time concepts.
TCI is the control part of TTCN-3 standard. It includes standardized interfaces for Component Handling (CH), Test Management (TM), Test Logging (TL), and gives access to the Codec (CD) to en/decode TTCN-3 test data.