 Deja Vu [32], is a system dedicated to the automatic programming of machinery in a control plant. In this system, its adaptation guided retrieval approach is fundamental. 

D. *Rule Based Expert Systems (RBR)* 
An RBR system has an inference engine that uses rules to reach conclusions based on premises and a certain context state. These systems are comprised of three main parts: 
inference engine, rule base, and working memory (auxiliary space in the memory to be used during the reasoning). [16], 
[17] 
An example of a rule based CDSS is MYCIN, one of the first systems to appear in the marketplace. This system counts with a knowledge base composed by IF-THEN rules, which are associated a certainty factor. Through these factors it can be given each rule different weights so as to determine their influence. [8], [9] 
Another example of a rule based CDSS is CASEY, which is an hybrid system that combines CBR and RBR. CASEY is a medical diagnostic system that offers a causal explanation of the patient's pathology. It is applied to heart failures diagnose. 

This system outstands by its use of rules, in both retrieving and reusing steps. [33] 
V. PROPOSED SOLUTION
A hybrid system has been developed, that combines CBR 
and RBR methodologies: SEDMAS-RBC-Adapt, whose ![0_image_0.png](0_image_0.png)

(IJCSIS) International Journal of Computer Science and Information Security, Vol. 7, No. 2, 2010 After that, the *learning* stage takes place. In this stage the information and knowledge obtained with the solution of the new case is *retained*, so as to be useful to solve future problems. This stage implicates a modification of the knowledge base, or of the methods to retrieve and reuse cases from such base. 

These systems progressively enlarge their knowledge bases with new cases while new problems are solved, gradually widening the range of situations in which the system is applicable and the accuracy of the proposed solutions. Once finalized the retention the cycle can start all over again. [19], 
[20] 
Regarding the *reutilization or adaptation* methods - main objectives of this research -, it is necessary to consider [19]: 
 Determine the differences between the new case and the previous case recovered. 

 Determine the aspects of previous cases that can be reutilized without changes. 

 Determine how to adapt a solution of a previous case based on the differences observed with the new case. 

The adaptation arises from: 1) the description of the new problem, 2) the solution provided for a similar problem, and optionally 3) the description of the corresponding similar problem. [18] 
The adaptation process must take into account two key issues: 1) How to identify what has to be adapted (identifying the adaptation need) and 2) how to choose an appropriate method to carry out a required adaptation. This last issue also implicates: identifying what must be changed, finding an appropriate adaptation technique or strategy, and choosing among a set of adequate strategies. [18], [4]. 

The most relevant adaptation techniques can be classified in three main groups: **a) Substitution methods:** null adaptation, re-instantiation, parameter adjustment, adjustment based on a fuzzy decision structure, local search, query memory, specialized search, case based substitution, restriction based substitution, user feedback based substitution; b) Transformation methods: common-sense transformation, model guided transformation and **c) Other methods**: 
adaptation and repairment with specific purposes, derivational replay, general framework for adaptations through substitution, case based adaptation, hierarchy based adaptation, compositional adaptation. [18], [20], [23], [22], [21], [24], [4], 
[25]. 

Each of these techniques or methods differ in complexity taking into account two issues: what is to be changed in the previous solution, and how will that change be achieved [21], [26] 
C. *CBR Systems Examples* DIAL [27], [28], [29], [30], [31], is a planning system for the recovery from disasters that stands out for its adaptation stage, that uses a combination of CBR and rules. It also implements the adaptation guided retrieval. 