Refinement-based verification of sequential implementations of Stateflow charts

Simulink/Stateflow charts are widely used in industry for the specification of control systems, which are often safety-critical. This suggests a need for a formal treatment of such models. In previous work, we have proposed a technique for automatic generation of formal models of Stateflow blocks to support refinement-based reasoning. In this article, we present a refinement strategy that supports the verification of automatically generated sequential C implementations of Stateflow charts. In particular, we discuss how this strategy can be specialised to take advantage of architectural features in order to allow a higher level of automation.Comment: In Proceedings Refine 2011, arXiv:1106.348

A systematic review of treatment outcomes in pediatric patients with intracranial ependymomas

ObjectEpendymoma is the third most common primary brain tumor in children. Tumors are classified according to the WHO pathological grading system. Prior studies have shown high levels of variability in patient outcomes within and across pathological grades. The authors reviewed the results from the published literature on intracranial ependymomas in children to describe clinical outcomes as they relate to treatment modality, associated mortality, and associated progression-free survival (PFS).MethodsA search of English language peer-reviewed articles describing patients 18 years of age or younger with intracranial ependymomas yielded data on 182 patients. These patients had undergone treatment for ependymoma with 1 of 5 modalities: 1) gross-total resection (GTR), 2) GTR as well as external beam radiation therapy (EBRT), 3) subtotal resection (STR), 4) STR as well as EBRT, or 5) radiosurgery. Mortality and outcome data were analyzed for time to tumor progression in patients treated with 1 of these 5 treatment modalities.ResultsOf these 182 patients, 69% had supratentorial ependymomas and 31% presented with infratentorial lesions. Regardless of tumor location or pathological grade, STR was associated with the highest rates of mortality. In contrast, GTR was associated with the lowest rates of mortality, the best overall survival, and the longest PFS. Children with WHO Grade II ependymomas had lower mortality rates when treated more aggressively with GTR. However, patients with WHO Grade III tumors had slightly better survival outcomes after a less aggressive surgical debulking (STR+EBRT) when compared with GTR.ConclusionsMortality, PFS, and overall survival vary in pediatric patients with intracranial ependymomas. Pathological classification, tumor location, and method of treatment play a role in outcomes. In this study, GTR was associated with the best overall and PFS rates. Patients with WHO Grade II tumors had better overall survival after GTR+EBRT and better PFS after GTR alone. Patients with WHO Grade III tumors had better overall survival after STR+EBRT. Patients with infratentorial tumors had improved overall survival compared with those with supratentorial tumors. Progression-free survival was best in those patients with infratentorial tumors following STR+EBRT. Consideration of all of these factors is important when counseling families on treatment options