Traceability in SCADE Suite Models
Traceability between all lifecycle artifacts is one of the mandatory requirements by CENELEC standards. As the main design work and verification activities are handled in SCADE Suite in openETCS traceability has to be established to link all requirements to the different developed SCADE models and to respective test specifications and verification reports.
The EN 50128 defines traceability as "degree to which a relationship can be established between two or more products of a development process, especially those having a predecessor/successor or master/subordinate relationship to one another". In 5.3.2.7 it is required that for each document a unique reference number and a relationship with other documents shall be defined and documented.
To establish traceability we are using ProR to manage requirements and the SCADE LifeCycle Requirements Management Gateway to create trace and reports. The following parts provide a short introduction how to use this tools to create trace between SUBSET-026 and SCADE Suite models. Furthermore, a detailed example is given, how the verification for the first model iteration from WP 3 shall be supported through the traceability tools and how this results can be analysed. Based on this process for the first iteration release a combined working process to establish traceability and to analyse coverage shall be outlined for the upcoming third iteration release.
As a central point for validation the EN 50128 states that throughtout all lifecycle phase means shall be available to show traces. Thereby, EN 50128 6.5.4.15 particular express 3 kinds of traceability, which also shall be taken into account by configuration management:
- traceability of requirements to the design or other objects which fulfil them,
- traceability of design objects to the implementation objects which instantiate them.
- traceability of requirements and design objects to the tests (component, integration, overall test) and analyses that verify them.
The trace to fulfill these needs shall be established during the lifecycle phase and always prior to verification/validation as the EN 50128 6.5.4.16 requires. Only under special circumstances it is acceptable if traceability is established after implementation of code.
For non-traceable objects of requirements, design or implementation it has to be demonstrated that no impact on safety or integrity of the system exists.
Main Input are the SUBSET-026 System Requirement Specifications. These will be used as ReqIF, which can be managed via the ProR part in the openETCS tool (or ProR Studio as the stand alone). The ReqIF SUBSET-026 Requirements files (8 reqif-files for SUBSET-026-1-8) have been genrated based on the Baseline 3.3 doc files by Moritz Dorka (@morido). All related information can be found in his subset026reqif repository. The current Version (v0.3) of the ReqIF Subset-026, whcih shall be used for traceability, will be provided in the subset26 directory.
Additional requirements shall also be provides in a usable requirements file format, best reqif. Depending on amount and character this can be done manually or by transformation. (If this is not suitable the requirements shall be provided in a format which can be at least handled in the SCADE lifecycle tool.)
To enable the Requirements Management Gateway to identify all requirements and their attributes in the ReqIF SUBSET-026 Requirements files the document structure has to be specified in a type. This has been done by Jan Welte (@janWelte) and is provided via the Subset26_ReqIF.types file which will be provided in the subset26 directory.
All SCADE models are developed by WP3 by following the respective development process and their modeling guidelines. These files are provided via the modeling repository and handed over according to the release plan by using git tags and releases.
The source code in C is generated via the SCADE code generator based on its design models.
All traces between Requirements and Design Models as well as to further artifacts shall be established using the SCADE LifeCycle Requirements Management Gateway (which is a version of Reqtify tailored to SCADE). For every SCADE model a traceability project is established which enables the designer (or verifier) to mark traces between single requirements and signal model objects. To do this the general coverage relation between a respective ReqIF SUBSET-026 file and the SCADE Suite project has to be configured in the traceability project.
The overall coverage can be analysed by WP4 via a traceability project relating the main SCADE model directory to all requirement files. All traces created for the separate SCADE projects (.etp) will be summed up, to show the overall coverage. Based on these traces the SCADE LifeCycle Requirements Management Gateway can create required reports as a traceability matrix or up- and downstream impact analysis. In addition specific rules can be specified to receive in-depth analysis of the coverage and to generate customized reports.
This sectipon gives a short introduction how to create traces for all openETCS SCADE Suite models. For more detailed information please look in the SCADE manuals.
To be able to identify all requirements in the SUBSET-026 ReqIF Requirements you have to provide the type to the SCADE lifecycle tool. To do this copy the file ReqIF_SUBSET-026.types for the subset26 directory to your SCADE projects directory.
To initially create a traceability project open your SCADE Suite project and push the Manage Requirements-button. Afterwards accept the notification that the project will be created. (If a project already exists it will open.)
After our acceptance your new traceability project will be opened. To be able to see see the requirements you want to cover with your SCADE Suite project the overall coverage relations have to be configured. This is done in the Configuration Window which can be opened by pushing the configuration button.
Every new traceability project will be initiated including the SCADE Suite model it has been created for and a Requirements document in a word format, which shall be covered. This requirements document has to be change to the correct SUBSET-026 file, which shall be covered by your SCADE Suite project. To do so the type of the requirements document has to be set to the current ReqIF SUBSET-026 type (ReqIF SUBSET-026 v0.3). Afterwards you have to choose the reqif file from the subset26 directory which shall be covered. If more requirement file shall be covered new documents can be added and be related to the SCADE Suite project. For a clear definition of all documents the name should be changed to the file name.
If the new configuration has been established and applied the traceability project should be able to analyse all trace between SCADE model and requirements.
Trace between single SCADE objects in the SCADE Suite project and requirements have to be set in the SCADE Suite environment. The Requirements Window can be opened via the tool bar button. If not all requirements are show in the window update the connection via the button in the top left corner. To set a link the SCADE object in the model explorer and the requirement in the requirement window have to be chosen. The link button in the requirement window creates the relation which is displayed in the lower part of requirements window and in the traceability view for the SCADE object properties. A link can also be created by dropping the requirement on the SCADE element.
As the traceability configuration was not available for the First Iteration Release all traces shall be established by WP4 during its verification.
For this work the branch tbd in the modeling repository has been established. The overall coverage is tracked via the tbd traceability project.
As the traceability configuration has not been available during the main work of the Third Iteration Release most traces shall be established afterwards. The resulting traceability projects for all SCADE projects shall be established for the future work. In addition WP4 will establish traces to all test and verification/validation objects already created in SCADE as far as this is reasonable.
The overall coverage and additional rules are tracked via the tbd traceability project. All created reports are stored in tbd directory.
All traceability projects established for the Third Iteration shall be continued and extended as required. For every new part of the SCADE model new traceability projects have to be created to enable the designer team to establish all required traces. WP 4 will continue and extend the traceability analysis via the overall traceability project. All other V&V artifacts shall be integrated into this project as possible.