Add work on frameworks

1-Intro/README.md

@@ -17,7 +17,7 @@ The task of solving a specific human-like problem, such as determining a person'
 
 One of the problems when dealing with the term **[Intelligence](https://en.wikipedia.org/wiki/Intelligence)** is that there is no clear definition of this term. One can argue that intelligence is connected to **abstract thinking**, or to **self-awareness**, but we cannot properly define it.
 
-[Photo of a Cat](images/photo-cat.jpg) | To see the ambiguity of a term *intelligence*, try answering a question: "Is a cat intelligent?". Different people tend to give different answer to this question, as there is not universally accepted test to prove this true or not. And if you think there is - try running your cat through an IQ test...
+![Photo of a Cat](images/photo-cat.jpg) | To see the ambiguity of a term *intelligence*, try answering a question: "Is a cat intelligent?". Different people tend to give different answer to this question, as there is not universally accepted test to prove this true or not. And if you think there is - try running your cat through an IQ test...
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 However, when speaking about AGI we need to have some way to tell if we have created a truly intelligent system. [Alan Turing](https://en.wikipedia.org/wiki/Alan_Turing) proposed such a way called **[Turing Test](https://en.wikipedia.org/wiki/Turing_test)**, which also acts like a definition of intelligence. The idea of such a test is that we compare our system to something inherently intelligent - a real human being. And because any automatic comparison can be easily bypassed by a computer program - we use human interrogator. So, if a human being is unable to distinguish between a real person and a computer system in text-based dialogue - the system is considered intelligent. 
@@ -26,4 +26,19 @@ However, when speaking about AGI we need to have some way to tell if we have cre
 
 ## Different Approaches to AI
 
-If we want computer to behave like a human, we probably 
+If we want computer to behave like a human, we need somehow to model inside a computer our way of thinking. Consequently, we need to try to understand what makes a human being intelligent.
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+There are two possible approaches to this problem:
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+Top-down Approach (Symbolic Reasoning) | Bottom-up Approach (Neural Networks)
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+Modelling the way a person reasons to solve a problem. It involves extracting **knowledge** from a human being, and representing it in a computer-readable form. We also need to develop a way to model **reasoning** inside a computer. | Modelling a structure of a human brain, consisting of huge number of simplest units called **neurons**. Each neuron acts like a simple weighted average of its inputs, and we can train a network of neurons to solve useful problems by providing **training data**.
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+There are also some other possible approaches to intelligence that we will mention here, but the two above are the main ones.
+### Top-Down Approach
+
+In **top-down approach**, we try to model our reasoning. People tend to have some rules in their head, for example, when a doctor is diagnosing a patient, he may realize that a person has a fever, and thus there might be some inflammation going on in his body. By applying a large set of rules to a specific problem a doctor may be able to come up with the final diagnosis. 
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+This approach relies heavily on **knowledge representation** and **reasoning**. Extracting knowledge from a human expert might be the most difficult part, because a doctor in many cases would not know exactly why he or she is coming up with a particular diagnosis. Sometimes the solution just comes up in his/her head without explicit thinking. Some tasks, such as determining the age of a person from photograph, cannot be at all reduced to manipulating knowledge.
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+Another