Week 13 notes completed

CM3010 Databases and Advanced Data Techniques/Week 13/Week 13 notes.md

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+# Semantic Databases
+The meaning that we have in common can be shared more effectively and we can communicate structures and information between databases
+
+# Semantic databases - What does a table actually tell us
+
+Sharing a Relational database
+
+* Just data
+  * CSV
+  * A table in a RDB, the data in the table but also the column specification
+  * The CSV file is the data but not the relation
+* Full relation (data and data types)
+  * Database dump (.sql)
+
+Example
+
+SF Movie Locations
+* Actor1, Actor2, Actor3
+  * Personal name
+  * An actor
+* Year
+  * Year is a positive integer
+  * Year is a calendar year
+* Location
+  * Text
+  * Geographical location
+    * In San Francisco
+
+### Layers of meaning
+* Data type
+  * string, integer, float
+* Data domain
+  * place, person, date
+* Data semantics
+  * Person acted in film
+
+The more meaning we can specify, the more we're able to spot when someone else is specifying the same meaning.
+
+### Shared meaning
+* Share data
+  * e.g. a .csv file
+* Share difinitions
+  * Data entry documentation
+* share syntax
+  * Validate new data. Agreements how we'll encode our information so new entries are accepted
+* Share machine-readable semantics
+
+### Deductive database
+First order logic:
+
+`ancestor(c, a) <- parent(c, a)`
+
+`ancestor(c, a) <- parent(c, b) AND ancestor(b, a)`
+
+`sibling(a, b) <- parent(c, a) AND parent(c, b)`
+
+In this example:
+
+`<-ancestor('Anakin', 'Kylo')`
+
+It won't look for explicit '___ is ancestor of ___' but it will look for the relation.
+
+## Sharing meaning in the real world
+### Common semantics
+* Shared documents(s)
+* Formal specifications
+* Human-readable definitions
+
+We always need realiable ways of sharing:
+* Information
+* Structures and semantics in computer-readable form
+* Structures and semantics in a human-readable form
+
+With these three, we can start to communicate and share meaning.
+
+For example, STEM a music notation, tries to convey the last two (computer and human-readable)
+
+![stem](Files/stem.png)
+
+A specification document in human-readable form:
+
+![Diagram](Files/prov.png)
+
+## XML - Documents with semantics
+eXtensible Markup Language
+
+Example of text that has been marked up:
+![Diagram](Files/xml1.png)
+Atributes
+![Diagram](Files/xml2.png)
+There always needs to be a parent node betcause documents are trees:
+![Diagram](Files/xml3.png)
+![Diagram](Files/xml4.png)