Issues in Mapping HRT-HOOD to UML Silvia Mazzini, Massimo D’Alessandro Intecs HRT via L. Gereschi 32-34 I-56124 Pisa, Italy silvia.mazzini@pisa.intecs.it Marco Di Natale, Giuseppe Lipari Scuola Superiore S.Anna viale R. Piaggio 34 I-56025 Pontedera, Italy marco,lipari @sssup.it Tullio Vardanega Universit` a di Padova via G. Belzoni 7 I-35131 Padova, Italy tullio.vardanega@math.unipd.it Abstract HRT-HOOD has methodological strengths that deserve to be preserved in the face of the commercial decline of HOOD technology. The UML meta-model, on the other hand, has a level of flexibility that makes it an especially attractive platform to express the specific real-time design minded features of the HRT-HOOD method. The object- oriented connotation of the method that results from map- ping HRT-HOOD onto UML raises methodological issues that we deem of interest to the real-time community at large. This paper discusses three such issues in particular: the prevalence of objects over classes in real-time design, with the consequent inversion of the standard object-oriented de- velopment paradigm; the need to derive classes “by ex- ample”, which arises from the demand to allow multiple, yet static, instances of real-time objects initially designed as singleton; the opportunity of reuse-oriented component- based real-time development, which descends from using interfaces instead of classes as the target of associations among objects. 1. Introduction A query for HRT-HOOD [3, 4] on popular search en- gines currently scores in the range of 300 to 600 significant hits. This score arguably attests the varied use that HRT- HOOD has attained as a reference term, a teaching aid and an industrially-applied method. Albeit originated from within the niche market of the somewhat esoteric HOOD community, HRT-HOOD ex- hibits two distinguishing features that make it especially significant to the real-time domain: (i) it encompasses a well-defined process model, with the discipline and rigour that are paramount to the development of high-integrity real-time systems; (ii) it promotes design conformance to a computational model that facilitate static timing analysis; a most attractive instance of computation model especially suited for HRT-HOOD is the recently emerged Ada Raven- scar Profile [1, 2], the consolidation process of which was effectively prompted by the definition of the method. The simultaneous occurrence of the commercial obso- lescence of the HOOD technology offer (not the discipline, though!) and the massive advent of the UML one [10] offers the opportunity for a thorough reflection on whether and how the “goodies” of HRT-HOOD can be migrated to and, possibly, augmented by the UML meta-model platform. Exploring this opportunity was the objective of a re- search project recently sponsored by the Italian Space Agency, with the authors as the main actors. This project defined an HRT-UML method that preserves the distin- guishing features of HRT-HOOD while also importing use- ful characteristics from pure object-oriented design. We believe that the embedding of selected object ori- entation characteristics into the process of real-time design raises issues of interest to the real-time community at large. In this paper, we undertake to illustrate the nature of those issues and the way we have addressed them in the definition of the HRT-UML method. 2. Setting the Scene The UML has been designed from the outset as a wide- ranging, general-purpose modeling language, aimed to a va- Proceedings of the 15th Euromicro Conference on Real-Time Systems (ECRTS’03) 0-7695-1936-9/03 $17.00 © 2003 IEEE Authorized licensed use limited to: UNIVERSITA PISA S ANNA. Downloaded on October 7, 2008 at 6:46 from IEEE Xplore. Restrictions apply.