added README

exam/ex01/README.rst

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+Wikipedia Link Graph Analyzer
+*****************************
+
+.. contents::
+
+Configuration
+=============
+
+Configuration is done in the file ``cfg.py``. There one can
+specify whether the system should use a sqlite or a mysql
+backend. Using the sqlite backend is faster for fetching the
+data because sqlite omits implicit keys. However when one
+wants to analyze the data using SQL instead of the pure
+python implementation mysql is faster.
+
+It is recommended to use sqlite for fetching the data, then
+transferring it to a mysql database and use this database
+for analyzing. 
+
+The main options in ``cfg.py`` are whether to use mysql or
+sqlite and options for those systems.
+
+Invocation
+==========
+
+Before invocating the program one should make sure that the
+`configuration`_ is correct, in particular whether the cache
+directory and cache name are set correctly for sqlite and
+the mysql connection information is correct.
+
+Then one must edit the name of the article to analyze around
+and the depth to receive the links. After this is done the
+link graph can be received (using ``python3 main.py``).
+
+It might be necessary to run this part several times if the
+program was unable to fetch all links. One can check for
+unreceived data by executing ``SELECT COUNT(*) FROM
+failed_to_fetch``. The result should be 0.
+
+Then the script uses Dijkstra's Algorithm in width-first
+mode to analyze the graph. By default this is done
+in-memory, it is however possible to do it with SQL. Using
+SQL is recommended only, if the data exceeds the RAM, as it
+is way slower.
+
+