2.5 Comparative Analysis
Machine Learning offers the ability of discovering
data patterns and possible associations between the
input data. It is also possible to apply different techni-
ques, from artificial neural networks to learning clas-
sifier systems. Machine Learning approaches can suf-
fer from performance issues, due to processing a large
input dataset (mandatory) or indexing data updates. It
is necessary to train the system with several examples
(large dataset), in order to reduce the risk of bad le-
arning, incorrect calculations and to minimize system
performance issues.
Decision Trees can become very big structures if
the number of characteristics and relations between
the data is very large. As such this poses a perfor-
mance issue as computations will become more com-
plex, the greater the tree is. Operations like recompu-
ting a tree, in order to represent a new variable or va-
lue will have a greater delay, diminishing the perfor-
mance of the overall system. However, this approach
is intuitive and easy to learn and use. It is also pos-
sible to represent data such as a hierarchical structure
with levels. It is also possible to combine decision
trees with other different techniques.
Fuzzy Inference is a process which is both flex-
ible and intuitive. It represents a natural way of ex-
pressing uncertain information (possibility of incom-
plete data). This system however can have poor per-
formance due to a large amount of fuzzy inference
rules. The system is also prone to error if the fuzzy
inference rules given are too generic or too specific.
These process can be used in combination with other
techniques, like machine learning.
Bayesian network is a graphical model that repre-
sents probabilistic relationships among variables and
that applies the Bayesian probability. With a Baye-
sian network it is possible to handle incomplete data
sets, learn and infer knowledge about a set of casual
data relationships. It allows the representation and in-
formation extraction from two factors that are belie-
ved to be correlated (a priori knowledge). It is also
possible to update the weight of the directed edges,
based on new data. There are disadvantages associ-
ated as: the computational difficulty of exploring a
previously unknown network, due to the need of cal-
culating all the branches of the network to obtain a
value of one branch. The second disadvantage is that
the prior knowledge must be reliable to have a use-
ful network. An excessively optimistic or pessimistic
expectation of the quality of these prior beliefs, will
distort the entire network and invalidate the results.
2.6 WebMD Symptom Checker
This application has the purpose of inferring a list of
possible conditions, indicated by a set of questions
performed to a user such as: age, gender, followed
by a series of questions including a part of the body
where symptoms occur. A user must answer the fol-
lowing questions to obtain a more precise diagnosis,
however the system is able to determine a possible
diagnosis in cases of lack of information. After pre-
senting the list with all the possible conditions, if a
user clicks on a condition will be presented to him
more information about that condition,(how common
is the disease, the degree of severity, among others).
This application is also able to point the most suitable
medical doctors (specialists) to deal with that condi-
tion. A user is able to choose the feature that will be
responsible for ordering a set of medical doctors, ran-
ging from name, years of experience to distance. Here
the user’s preferences are taken into account at the
time of decision (WebMD, 2017a; WebMD, 2017b;
Whysel, 2012).
2.7 Isabel Symptom Checker
This application is responsible for promoting the
search of medical knowledge to all people, using
the professional Isabel Diagnosis Check-list System,
used by doctors around the world when they’re unsure
of a diagnosis. To obtain diagnosis information it is
only necessary for a user to indicate his symptoms
(unlike most symptom checkers, a user can put in as
many symptoms as he wishes) and it will be provided
a list of the most possible diagnoses that are related to
those symptoms. Each diagnosis has medical infor-
mation associated that complement and explain dise-
ases, treatments and other symptoms. It can also be an
auxiliary way to understand, obtain more information
about a health care status, in order to discuss a possi-
ble health topic with a medical doctor. It is also possi-
ble for a user to find a doctor, offering a functionality
composed by a set of links to various web resources
that offer this functionality. These links take into ac-
count the medical specialty obtained and location, in
order to return the most relevant medical doctors (Isa-
bel, 2017).
2.8 Mayoclinic Symptom Checker
This application is responsible for providing informa-
tion, not diagnosing, a given symptom. The idea is for
the patient to initially choose a symptom. After choo-
sing the symptom, a user needs to point at least one
related factor, in order to complement the information
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