Update README.md

README.md

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 [![License](https://img.shields.io/badge/license-MIT-blue.svg)](https://raw.githubusercontent.com/digiaonline/graphql-php/master/LICENSE)
 
 A PHP7 implementation of the [GraphQL specification](http://facebook.github.io/graphql/).
+
+## Requirements
+
+- PHP >= 7.0
+
+## Motivation
+
+TODO
+
+## Architecture
+
+### Packages
+
+#### Execution
+
+Takes care of executing operation against a GraphQL schema.
+
+Package lead: [@hungneox](https://github.com/hungneox/)
+
+### Language
+
+Defines the GraphQL language and the associated AST.
+
+Package lead: [@crisu83](https://github.com/crisu83/)
+
+#### Parsing
+
+The plan is to encourage developers to use the official GraphQL parser written C++ through a PHP extension because
+its performance is outstanding. However, we will also provide a shim for the parser, which allows developers to use 
+this library without installing a custom PHP extension in their environment.
+
+The official GraphQL parser takes a GQL string as its input and returns the corresponding Abstract Syntax Tree (AST)
+(an associative array in PHP) as its output. Most of the GraphQL implementations (across all languages) takes a
+different approach where they convert the AST directly into nodes (class instances in PHP). While this approach might 
+be a bit faster, it couples the parser tightly with the rest of the library, which we think is short-sighted. 
+Instead we decided to take a different approach, where the parser produces the AST as an associative array. This allows 
+the developers to switch out the bundled parser for the parser written in C++ without changing a single line of code.
+
+#### AST representation
+
+We also believe that all libraries should be easy to extend so we decided to introduce a builder system using the 
+Builder pattern for converting the AST into nodes. This approach allows developers to implement their own builders if 
+the specification would change in the future, without changing a single line of code in this library.
+
+#### Type system
+
+Describes the GraphQL type system and schema definition.
+
+Package lead: [@crisu83](https://github.com/crisu83/)
+
+TODO
+
+## Usage
+
+TODO