19SafQB

8.9 The Need of Methods and Tools and Corresponding Research 305
Practice has proven that it is cheaper in the long-run, but even in the shortterm
there are clear benefits. Rushed, corner-cutting, muddled-headed standardization
efforts with repeated returns to square one are, unfortunately, an
expensive, time-wasting reality. However, these are the exceptions, rather than
the rule.
There is a need for the application of pragmatic specification techniques
and good working practices adapted, if necessary, for particular needs.
To avoid the kind of problems identified in previous section, advice is
given on how to:
• develop clear requirements;
• develop a comprehensive architectural overview, including clear
identification of interoperable interfaces;
• concentrate on specifying the right things, i.e. interoperable interfaces,
and resist detailing internal implementation;
• use good protocol design techniques, such as
◦ separation and description of normal behaviour and
behaviour under error conditions;
◦ full specification of options, including consequences of not
implementing options;
◦ development of (interoperability) profiles, where appropriate;
◦ full specification of data (messages) and the encoding of
that data;
• plan for validation and testing.
Solutions can range from the use of well-structured prose, with the correct
and consistent application of the drafting rules (e.g. the use of the words shall,
should, etc.), to the judicious application of modelling techniques, tools
and languages such as:
• Unified Modelling Language (UML) for requirements specification;
• Message Sequence Charts (MSC) for the specification of information
flows;