The next version of SysML, the modelling language based on UML for Systems Engineering projects, should be released in June as version 1.3 beta is currently listed on the OMG.org website.
Even though SysML 1.3 beta specifications aren’t released yet, it’s already covered in the Second Edition of “A Practical Guide to SysML” book by S.Friedenthal, A.Moore, and R.Steiner (ISBN : 0123852064).
SysML 1.3 main changes apply to ports, distinct interaction points on Blocks. In the current version (SysML 1.2), there are two types of ports: standard ports to describe service oriented peer-to-peer interaction through provided/required interfaces, and flow ports to describe items that can flow in and out the block.
Flow ports and Port specifications are deprecated in version 1.3, but the concepts remain: SysML 1.3 replaces them with two new types, Full Ports and Proxy Ports, both allowing to combine operations to call, and items to flow in and out the block.
Full ports
- A full port represents a part that has been placed onto the main block’s boundary so it can be accessed from external blocks; hence this part is no longer shown inside the main block but as a full port.
- A full port is typed by a block to define its properties i.e. operations to call and/or items that can flow in and out the block. A full port therefore combines both SysML 1.2 flow ports and standard ports, and no longer requires the ball and socket interface notation.
- Full ports can be conjugated like SysML 1.2 flow ports to reverse the direction of items ; it has the same effect on operations i.e. it will change provided features (supported by the owning block) to required features (operations that must be supported by other blocks)
Proxy ports
- A proxy port acts as a surrogate or placeholder to route all requests to the real port that provides these features (operations, items) ; this port may belong to the main block or an internal part
- A proxy port does not implement any feature, nor is it a block internal part
- Proxy ports are typed by Block Interfaces to specify the available features (items and/or operations)
Nested ports & nested flows have been introduced in SysML 1.3 to specify an additional level of ports within a port. As shown in the following diagram, the port p1 has two nested ports to associate external blocks directly with the AC in and Audio out.
To define nested ports, the block’s port is type by a block that owns ports.
- Association blocks have also been introduced in SysML 1.3 to specify port compatibility in order to ensure that connecting ports from different blocks doesn’t violate any constraint. This is modelled by creating an association block between two interface blocks, and then choosing this association block as the type for a connector between the 2 proxy ports:
Conclusion
SysML 1.3 has revised the concept of Ports to provide a more complete approach and definition compared with version 1.2. For instance it prevents from duplicating ports when a Block both needs to provide or require operations and have items to flow in/out.
This approach could have a significant impact on how you organize and model your system since interfaces are no longer exposed by ports. Instead, it will the block used as the type for the full port, that will realize or use interfaces, or itself own operations.
Once SysML 1.3 is available, it will be interesting to see how SparxSystems will implement it in Enterprise Architect so these new features are easy to use (e.g. with the IBD, to move an internal part of the block to a full port). A feature to easily convert a project from SysML 1.2 to 1.3 whilst keeping a good control over the changes would be useful..