## 1 Introduction  
In the domain of medicine in general, and physical medicine and rehabilitation in particular, several standard terminologies and classifications exist [1] that can be used for knowledge representation and integration. Some examples are: the _systematized nomenclature of medicine--clinical terms_ (SNOMED CT) [2]; the _unified medical language system_ (UMLS); GALEN; the _international classification of diseases_ version 10 (ICD-10) [3]; and the _international classification of functioning,disability and health_ (ICF) [4] defined by the _World Health Organization_ (WHO). In particular, the use of the ICF for measuring the functioning status and diversity with _multidimensional_ indicators, at both individual and population levels, can contribute to solve interoperability problems among health institutions that employ different measuring questionnaires. The ICF framework classifies concepts of functioning, disability and health and specifies their range of values. In rehabilitation, which is a multidimensional process, the ICF is useful to achieve comparable and interoperable data collections [5] and is suitable for knowledge representation in _clinical decision support systems_ (CDSSs), together with information models such as the _virtual medical record_ (vMR), to contribute to solve interoperability problems in the electronic exchange of clinical information.  
We designed and developed a CDSS which uses standard concepts and relations to represent and reason about patients' health status. For the decision-making process, a _knowledge-based system_ (KBS) is used with _case-based reasoning_ (CBR). In CBR, the two main types of case representation are _points_ and _series_. Two key issues when cases are time series are the choice of _representation methods_ and _similarity measures_. Regarding the series-based representation, various types of data abstraction [6] and time granularities can be used. Although many similarity measures have been proposed for time series [7], only the Euclidean distance is used in this paper, this being the first attempt to apply CBR to the rehabilitation domain. Our goals are:  
* to present an application in the rehabilitation domain, in particular, a CDSS for the prognosis of health status of chronic patients who suffer from neurological diseases in the extra-hospital stage;
* to describe how the ICF, ICD-10, SNOMED CT and vMR can be used to build interoperable CDSSs;
* to show the pros and cons of representations methods of cases; and
* to explain how the ICF and ICD-10 are used in similarity measures of functioning status and diversity.  
In the rehabilitation of people who suffer from neurological diseases, there are two basic stages: _intra-hospital_ and _extra-hospital_. In the intra-hospital (acute) phase, patients who suffered from a traumatic or non-traumatic injury stay in hospital undergoing rehabilitation. After typically a few months in hospital, they return home and the extra-hospital phase starts. Thereafter, they go once a year to the rehabilitation hospital for a _periodic integral evaluation_ (PIE), when they are administered several questionnaires (depending on the disease they are suffering from) with the aim of measuring functioning independence, psychological and social variables. In Section 3.2 we present examples of questionnaires administered in the PIE. This study is focused on the extra-hospital or chronic phase.