Start to answer questions in assignment 2

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@@ -30,9 +30,49 @@ Draw a composite usage map for the RVH database.
 
 Answer the following questions (250 words max/question).
 
-* What are the typical integrity controls performed in both data integrity and referential integrity?
-* Using an example for each situation, illustrate the three common situations that suggest relations should be denormalized.
-* What are the advantages and disadvantages of horizontal and vertical partitioning?
+**What are the typical integrity controls performed in both data integrity and referential integrity?**
+
+* default value
+* range control
+* null value control
+* referential integrity control
+
+**Using an example for each situation, illustrate the three common situations that suggest relations should be denormalized.**
+
+1. Two entities with one-to-one relationship
+  ```text
+    User(id: integer, username: string, password_digest: string, profile_id: integer)
+    Profile(id: integer, first_name: string, last_name: string, email: string)
+  ```
+
+  If a web site displays the currently logged in users `username` and `email` address
+  on all pages, then it might make sense to de-normalize this data to reduce the need for
+  an INNER JOIN on the two tables to render every screen.
+
+2. A many-to-many relationship with nonkey attributes
+  * E.g.
+3. Reference data
+  * E.g.
+
+
+**What are the advantages and disadvantages of horizontal and vertical partitioning?**
+
+* Horizontal Partitioning
+  * Advantages:
+    1. Efficiency: Data queried together are stored close to one another and separate from data not used together.
+    2. Local optimization: Each partition of data can be stored to optimize performance for it's own use.
+    3. Security: Data not relevant to one group of users can be segregated from data those users are allowed to use.
+    4. Recovery and uptime: Smaller files take less time to back up and recover and other files are still accessible if one file is damaged, so the effects of damage are isolated.
+    5. Load balancing: Files can be allocated to different storage areas, which minimizes contention for access to the same storage area or even allows for parallel access to the different areas.
+  * Disadvantages:
+    1. Inconsistent access speed: Different partitions may have different access speeds, thus confusing users. If data needs to be accessed across partitions, this produces slower response times.
+    2. Complexity: is usually not transparent to application code, which requires knowledge of which partition to read/write from.
+    3. Extra space and update time: Data may be duplicated across partitions, taking extra storage space compared to all data in normalized files. Updates that affect multiple partitions will be slower.
+* Vertical Partitioning
+  * Advantages:
+    1. Efficiency: Data queried together are stored close to one another and separate from data not used together.
+  * Disadvantages:
+    1. More joins are needed in order to gather the required data reducing query speed or increasing the need for more indexes which increases the amount of needed disk space.
 
 ## Question 3 (12 marks)