ReqIF – Standard for Automated Interchange of Requirements
(The following article was originally published in Digital Engineering Magazine, edition 5/15, page 50)
The automobile industry is facing a challenge that applies not just to it alone – but this is an industry where it looms particularly large. The act of laying down requirements for a vehicle component in the specifications and agreeing on these with suppliers and partners becomes increasingly difficult as the complexity of the product concerned rises. To deal with this challenge, manufacturers in Germany have created an international standard for requirements exchange known as ReqIF (Requirements Interchange Format) brought about through the agency of HIS (Herstellerinitiative Software) and with the aid of the ProSTEP iViP Association. The task now is to utilize this standard.
The manufacturing industry is to a large extent distributed across the globe and therefore many companies must cooperate internationally in order to develop and manufacture both cars and aircraft. This cooperation is based on exactly defined requirements that are formulated by the manufacturer and the specifications often include many thousands of such requirements.
Fig. 1: The complexity of managing the requirements increases with complexity of the product
IT systems have been used for many years to record and manage requirements – in fact given the amount of change and coordination implicit in today’s requirements, another way to handle this is no longer possible, above all because the use of software has itself not only resulted in many additional requirements, but has also brought a previously unknown pace to development and the change process.
As in other sectors, a large variety of different tools are available. These include on one hand Requirements Management (RM) tools that concentrate on managing requirements – such as DOORS from IBM and Rectify from Dassault Systèmes – while on the other, the requirements themselves form part of almost all current ALM (Application Lifecycle Management) and PLM systems, for example Integrity from PTC or Teamcenter from Siemens Industry Software, to name just two of the larger suppliers.
Over a longer period, DOORS more or less established itself as a standard among manufacturers. But a DOORS add-on tool from IBM, originally conceived for the exchange of requirements for various tools, is now itself being used between differing versions of the software, because these versions differ in the scope of their functionality. Exchange is even more complicated with suppliers because here many other tools are in use that utilize different languages.
The benefits of digital specifications
A set of digital specifications consists of those specifications that, for example for a controller describes exactly the functions it must execute – in the case of an entertainment unit, it must therefore be able to support the display of specific maps. An RM tool such as DOORS not only permits the formulation of requirements in words, it can incorporate graphics and 3-D models. To do so it utilizes the Rich Text Format (RTF) and supports OLE (Object Linking and Embedding) as developed by Microsoft. Moreover, a number of arbitrary links between requirements can be generated and managed, these of course being extremely important when it comes to interchange between the client and the supplier.
This works for two users using the same version of the same software, but between all others a loss of information is preprogrammed. Firstly, not all support RTF since some use different text formats. Secondly, OLE is not supported by all, and finally, there is no uniform procedure regarding, for example, the attributes that are stored along with the specification and with whose help communication between the partners regarding requirements is undertaken.
It can be seen that digital specifications behave similarly to CAD models used in development: 70 to 80 percent of all requirements once designed can and must be reused according to an estimate by Stefan Tautz, IT Project Manager at Continental responsible for data exchange in requirements management. In this respect it is not sufficient to carry out an exchange on a one-time basis. Similar to 3-D models, requirements are very much living entities and continually change their content, so this implies that the associated data exchange must be regarded as an ongoing occurrence.
Fig. 2: The history of RIF and ReqIF up until now
This is the reason why, under the name of Requirements Interchange Format (RIF) (see Fig. 2), the HIS (Herstellerinitiative Software) in Germany began work in 2004 on a neutral exchange format. The specification was handed over to the ProSTEP iViP Association in 2008 to be implemented as an internationally recognized standard, a goal that was achieved in 2011 – only three years later. To avoid misunderstandings with regard to another standard, the new norm was given the acronym ReqIF by the Object Management Group. RIF itself was not developed any further. The ReqIF standard not only offers technical advantages, for example having only one "object" element for integration of non-text requirements by means of XHTML, whereas in RIF three different concepts existed, a situation that considerably increased the amount of data to be exchanged. Above all, however, ReqIF is an internationally recognized standard that is continually being improved and supported by an ever-increasing number of tool suppliers.
ReqIF contains an XML data model that permits automated transfer of specifications including graphics and tables. In addition, it includes clear rules for the description (and therefore also for the identification) of the data. With ReqIF, an exchange file is exported from an RM tool that can be imported and understood by another system (see Fig. 3). The system suppliers taking part must, of course, on their side offer the corresponding import and export functions.
A standard that encourages cooperation
For this purpose, the ProSTEP iViP Association set up the ReqIF Implementor Forum at the end of 2011, which primarily includes the suppliers of RM tools as well as users. Suppliers include IBM, PTC and Siemens as well as a range of system integrators and suppliers of services. This project group published a ReqIF Implementation Guideline in 2014 that has been implemented almost in its entirety by most ReqIF tool suppliers. This means that by means of the new standard, specifications, tables, attributes and links can now be automatically exchanged between different manufacturers and between differing software versions by utilizing a ReqIF Exchange File.
Returning to the example given above, the Implementation Guideline specifies how OLE objects can be exchanged even when a system participating does not support OLE and also how links or other associations between elements in a table or an attribute are exchanged.
Fig. 3: The challenge that HIS took up
Unfortunately, a standard does not establish itself automatically and those tools that are trusted are, as before, preferred. To utilize the standard, which is more powerful than RIF and many a tool, the partners must also agree to adhere as closely as possible to the standard in the use of their own systems. In this respect, ReqIF is the same as any other standard – it simplifies cross-company cooperation and in return demands a few changes in the daily work process.
Fig. 4: Daimler predicts that ReqIF will prevail. (Slide from the keynote address by Dr. Haasis)
VDA and the ProSTEP iViP Association have in an astonishingly short time succeeded in creating an important standard that is internationally accepted. Dr. Siegmar Haasis, CIO Research and Development Mercedes-Benz Cars at Daimler AG, presenting ReqIF in his concluding keynote address (see Fig. 4) at this year’s ProSTEP iViP Symposium in Stuttgart placed it at the same level as JT, the neutral 3-D data format that has played a large part in Daimler’s recent success in replacing its CAD system. He reported on a ReqIF pilot project that will be carried out this year together with Continental. He also called on manufacturers, suppliers and IT providers to support ReqIF and it is to be hoped that industry will follow this call. Particularly with regard to Industrie 4.0, much depends on how well industry handles requirements management for the new systems.