In February this year the UNIT Special Interest Group launched a Request For Comments process on a revised document containing the Unit Operation interface specification belonging to the documentation set of version 1.0 of the CAPE-OPEN standards. It was then version 6.21 of the document.

A number of comments were received especially from Process Systems Enterprise and the UNIT SIG is very pleased of the feedback provided. It prompted the UNIT SIG to revise some more the document and this led to version 6.25.

Version 6.25 is now ready for the formal approval process that starts with a Request For Comments step. The UNIT SIG is now seeking comments from the community in order to finalize the revision. Comments are welcome using the attached form (A Microsoft Word version of the interface specification document is available upon request made to ). The RFC period opens up on November 15, 2011 and is due to finish by December 15, 2011. The comments are to be sent to who will liaise with the UNIT SIG leader on the feedback obtained. Your feedback is of the uttermost importance: it will ensure that the revised specification meets your expectations in terms of clarity and ease of use.

Apart from a number of additional clarifications brought into the document on top of the ones already embedded in version 6.21, version 6.25 brings one major modification to the specification document.

Chapter 7 describes a versioning system that is introduced in order to resolve an issue with the communication between a UNIT component and a Process Modelling Environment (PME) about the version of the thermodynamic interfaces used by the UNIT component. This versioning system was elaborated by the Methods & Tools SIG and has been applied to the UNIT specification. It will force modifications in the registration mechanism of UNIT components supporting version 1.1 of the Thermodynamic and Physical Properties interfaces and may lead PME developers to modify their presentation of available UNIT components. So it is of major importance that this proposed modification be suitably reviewed.