Fundamental SKA Software Standards¶
These standards underpin all SKA software development. The canonical copy of this information is held in eB, but the essential information is on this page, which is extracted from the eB document.
Standards Applicable to all SKA Software¶
All SKA software shall have a copyright notice which is a description of who asserts the copyright over the software.
- Derived software and bespoke software will normally be comprised of code modules which have a mixture of copyright attributions. Some code modules will have joint copyright, and others have sole copyright, but the codebase in its entirety will have a mixture.
All SKA software shall have a software license which is a legal instrument governing the use or redistribution of software.
- Off-the-shelf software will normally have licenses over which the SKA has no control.
- Derived software may have mixture of licenses.
- Bespoke software will normally have a permissive open source license.
The documentation associated with SKA software shall also carry a license unless it is covered by the software license.
All software licenses governing a body of software must be mutually compatible.
All software licenses for SKA software shall be agreed with the SKA Organisation prior to the software being adopted or developed.
- The SKA Organisation will always agree to a 3 clause BSD license for software (provided there are no compatibility issues) and will favour open-source permissive licenses with attribution since they minimize compatibility issues.
- The SKA Organisation will always agree to a Creative Commons Attribution 4.0 International License for documentation (provided there are no compatibility issues).
- This permissive open source recommendation is significantly more permissive than the SKA IP policy [RD1] which only requires contributors to “grant non-exclusive, worldwide, royalty-free, perpetual, and irrevocable sub-licenses to other SKA Contributors to use those innovations and work products for SKA Project purposes only.”
- It is understood that the IP licensing environment of FPGA software is often substantially different to that of the open source software environment, with many (or most) developments relying on IP (from the FPGA vendor, for example) that has more restrictive licensing. In accordance with this standard, use of this IP, and its associated license, must be agreed with the SKA Organisation.
Standards applicable to Off-the-shelf software¶
All SKA Software which is off-the-shelf software shall have:
- A business case describing the requirements for the software, in comparison to other software.
- A record of the evidence that demonstrates that the software meets these requirements.
- A description of how the software will be supported during the
expected lifetime of the software.
- The SKA Observatory has a predicted lifetime of 50 years, which
is much longer than most software products and the
companies that develop them. Hence this description may
include: how many alternatives exist which also support the
software’s data products, escrow agreements and
commercial soundness of the company. Support includes:
- Managing unexpected behaviour of the software that is incompatible with the SKA Observatory’s (possibly evolving) requirements.
- Managing the evolution of underlying systems, such as hardware and operating systems, that the software depends on.
- Managing changes to the existing supplier support arrangements (e.g. the original company being acquired, the product becoming not commercially viable etc.).
- The SKA Observatory has a predicted lifetime of 50 years, which is much longer than most software products and the companies that develop them. Hence this description may include: how many alternatives exist which also support the software’s data products, escrow agreements and commercial soundness of the company. Support includes:
- Evidence that the software has been developed to a standard of quality appropriate to the needs of the SKA Organisation.
- Documentation that is appropriate to the needs of the SKA Organisation.
- Been approved by the SKA Organisation as to its fitness for purpose and included in a public register of approved SKA Software.
Standards Applicable to Bespoke Software¶
This section comprises standards relating to processes described by ISO 12207 [RD1], §7.1.2 (Requirements), §7.1.3 (Architecture) and §7.1.4 (Detailed Design). They complement any general System Engineering level standards (i.e. processes relating to ISO 15288 [RD2]) applicable to all SKA systems.
All SKA Software that is bespoke software shall have documentation, models and prototypes covering the following:
- The requirements the software is intended to fulfil.
- The software architecture used.
- The software architecture is the primary deliverable at CDR. Detailed design is only required to the extent needed for reliable cost estimation.
- The recommended reference for architecture documentation is “Documenting Software Architectures: Views and Beyond, Second Edition” (Clements et al, 2011) [RD3]. This book should be consulted for best practices on documenting views, styles and interfaces. The ISO 42010 [RD4] standard is also relevant.
- The architecture documentation should include, at minimum
- System Overview, including a description of the architectural styles used.
- A set of views describing key features of the architecture, and the mapping between views.
- Interface Documentation or references to applicable Interface Control Documents for the major interfaces.
- Rationale justifying how the architecture meets the requirements. Justification on the basis of models and evolutionary prototypes is highly recommended in many cases.
- A consideration as to whether there is any existing software that meets, or can be modified to meet, the requirements.
- Emphasis should be on clear, unambiguous diagrams with accompanying descriptions and tables.
- Refer to Chapter 11 of Clements et al for a description of interface documentation. Interfaces that are language or framework specific may be best documented in a format appropriate to that language or framework (e.g. generated from comments and code in an evolutionary prototype).
- Detailed design of components.
- It is expected that a significant amount of the detailed design may be automatically generated from code and comments.
- Detailed design documentation for FPGA software should include estimates of device utilization (DSPs, BRAMS, LUTs etc), details of clock rates and clocking domains and tracking of timing closure issues
The software design should be reviewed and the reviews should incorporate the following factors:
- The SKA Organisation is responsible for L1 requirements and must agree and review all L2 and L3 requirements.
- The SKA Organisation personnel should be involved in software architecture reviews
- The software architecture should be reviewed to demonstrate that it meets key requirements and provides sufficient detail for cost estimation and implementation.
- Both the architecture and detailed design reviews shall carefully
consider the requirements relating to the long lifetime of the SKA
Observatory. This includes, for example:
- Portability of the system across multiple architectures and operating systems.
- Consideration of the life-cycle of all dependencies, including development tools and run-time dependencies.
- The need for the system to be compatible with version 6 of the Internet Protocol.
- The careful design of API’s and the need to exchange data by API’s rather than relying on environmental assumptions about file systems, for example.
- Detailed design shall be reviewed:
- By someone in addition to the principal developer of the module being considered.
- In a manner appropriate to the significance of the module.
- The significance of the code relates to the impact any changes to the design has on other parts of the system.
- The review process must not be overly bureaucratic. Development teams should be empowered to design and develop the code efficiently and modify the internal design when required.
This section comprises standards relating to processes described by ISO 12207 (2008) §7.1.5 (Construction).
The construction of all SKA Software which is bespoke software shall include:
- The construction of all source code shall follow a defined
documented process that is approved by the SKA Organisation.
- The Software Engineering Institute Personal Software Process and Team Software Process are relevant processes.
- The process documentation shall include a workflow
description that follows accepted best practices. For
example, it is recommended that:
- Work management practices shall include the following:
- All work tasks shall be described in a ticketing system.
- Work tickets shall have a description of the task, an estimate of the resource required and amount of the task that has been completed.
- All code commits shall relate to a ticket in the ticketing system.
- The developing organisation shall be able to use the ticketing system to generate progress metrics.
- Code management practices shall include the following:
- With the exception of trivial cases (e.g. possibly documentation changes) code must only be added to or merged with the main development branch by a pull-request-like mechanism.
- The pull request (or similar mechanism) must only be accepted after the code has been cleanly compiled and passes all appropriate tests. This process should be triggered automatically.
- Pull requests must only be accepted after the code changes have been reviewed by more than one developer (inclusive of the primary developer).
- Pull requests must only accepted by suitably qualified individuals.
- Work management practices shall include the following:
- All construction software development shall utilise an SKA
Organisation approved version control system.
- The SKA Organisation approved version control system is Git.
- All documentation, source code, software source code, firmware source code, HDL source code, unit tests, build scripts, deployment scripts, testing utilities and debugging utilities must reside in the version control system.
- Release tags for code shall adhere to the Semantic Versioning 2.0.0 specification [RD8].
- Software shall be written in an SKA approved language and adhere
to SKA language specific style guides.
- The primary approved language shall be Python.
- The coding standards for Python will be adapted from the LSST DM code style guides [RD7].
- Use of other languages must be justified by, for example:
- Impossibility of running Python in the chosen run-time environment.
- Python doesn’t provide the necessary performance.
- Many other languages are likely to have extensive usage. For
- C/C++ (for high performance computation on conventional CPU’s).
- Java (e.g. for business logic in web systems and derived software).
- VHDL (for FPGA development).
- CUDA (for GPU software).
- OpenCL (for software that targets both GPU and FPGAs)
- SKA Organisation employees must have access to the repository while the software is under development, be able to sign-up for notifications of commits and, if necessary, give feedback to the developers.
- Test software verifying the system software at multiple
levels (from the complete system down to individual module unit
tests). Tests shall include verifying specific requirements at
different levels and, as far as practicable, be able to be run
- Tests shall be able to run in a continuous integration environment.
- For software targeting CPU’s this should include unit tests at the class, function or source file level to test basic functionality of methods (functions) with an agreed minimal coverage (between 75 and 90%). Unit tests created for fixing defects or making specific enhancements should be checked-in with a reference to the issue for which the tests were created.
- For FPGA software this should include:
- Each module shall be associated with a specific test bench.
- Modules shall undergo simulation with a predefined pass/fail criteria.
- Release builds shall be made up of verified functional blocks and handled in a scripted framework.
- Simulated and released code shall match the committed code. For example, committing the code shall not change register contents (even version numbers) in the source code.
- Software simulations/stubs/drivers/mocks for all major interfaces to enable sub-system and system level tests.
- Automated documentation generation - including, but not limited to
parts of detailed design documentation.
- Automated documentation generation software is generally off-the-shelf software and so subject to the conditions in section 4.
- Not all documentation can be automatically generated, but it should be used wherever it is reasonably practicable.
- The SKA Organisation shall accept ReST format documentation generated using Sphinx.
- A complete definition of other software (both off-the-shelf and bespoke) that the software requires to build and deploy.
- Deployment scripts or configurations, which allow the software
to be deployed cleanly and in as automated a fashion as is
practicable, starting with a bare deployment environment.
- For FPGA software, this means configuring an un-programmed FPGA device in the target SKA system. Deployment may require the use of the host based software delivered as part of the LMC system.
- The ability to log diagnostic information using SKA Log Message Format.
- The ability, dynamically at runtime, to suppress or select logging of messages at different Syslog severity levels on at least a per-process basis (and a per-thread basis or per class basis if appropriate).
- The ability to log diagnostics at all major interfaces at a RFC 5424 Debug severity level.
- Alarms, where applicable, shall be based on the IEC 62682 standard [RD6].
Acceptance and handover¶
This section comprises standards relating to processes described by ISO 12207 [RD1], §6.4.8 (Acceptance Support), §7.1.6 (Integration) and §7.1.7 (Qualification).
SKA software which is bespoke software will only be accepted by the SKA Organisation after it has been appropriately integrated and validated.
- The integration, validation and acceptance of all source code shall follow a defined documented process that is approved by the SKA Organisation.
- This process must make clear, for all times during the handover:
- Who is responsible for making software changes.
- What the expected turnaround time for software changes is.
- At the completion of the process all code shall have been:
- shown to pass appropriate, system, sub-system and unit level tests.
- shown to cleanly compile and/or build using an SKA Organisation provided build environment.
- checked into an approved SKA Organisation acceptance repository.
- Software shall be integrated, as far as possible, prior to the
integration of other aspects of the system.
- During the SKA construction, this means that it is intended for this to take place in advance of the SKA Array Release schedule.
- The intention is that this will be done by a series of integration “Challenges” which predate integration at an ITF, and continue through the array release period.
- During the handover period, there shall be a ‘bug fix’ workflow defined that is streamlined to allow critical fixes to be deployed quickly.
- When the SKA Organisation takes over maintenance of the software the complete repository, including commit history, shall be delivered to the SKA Organisation.
- Where code requires specialised hardware for testing, provision of this hardware, or demonstrably equivalent hardware, shall be included as part of the handover.
To develop and integrate software the SKA Organisation shall provide:
A central, globally visible, set of repositories that can be used by any SKA developers.
- These repositories will clearly define how to handle large binary data files.
A globally accessible website for the storage and access of documentation.
A continuous integration and test framework that is open to use by developers.
- It is intended that this will include support for at least the 4 types of bespoke software described in the scope section (Tango, SDP and NIP data driven software, FPGA software and Web Applications).
- The development of this will be done in conjunction with the pre-construction and construction consortia. The SKA Organisation will serve as an overall coordinator.
Communication tools to enable software developers to access expertise from all the SKA software developer community.
- This will include issue tracking, discussion fora etc.
A list of approved off-the-shelf software.
- To add software to this approved list, please email details of the software, the justification for its use, and the scope of its usage to the Head of Computing and Software at the SKA Organisation.
- The intention of this approved list is to aid standardisation.