Good Design for Historical source based Databases

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Good Design for Historical source based
Databases
Hamish James
History Data Service
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Databases

• A database is a computerised record keeping
  system.
• A DataBase Management System (DBMS) is a computer
  application built around a database that provides
  a flexible way of storing, manipulating, and
  examining data.
• A DBMS consists of data, hardware, software, and
  users
• A DBMS on a personal computer will provide
  facilities for
• inputting data, modifying, retrieving and
  deleting data
• querying the data (SQL)
• producing reports based on the data
• building front-ends for users

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Data Models

• Data models are abstract definitions of
  structures and relationships used to organise
  data in a database.
• Data models can be characterised by how they
  organise the connections between different
  records
• flat file
• hierarchical
• network
• relational
• object orientated
• Most DBMSs available for personal computers are
  either flat file or relational.

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Entity Relationship Modelling

• A data modelling technique that transforms
  information into a form that meets the
  requirements of the relational data model.
• Entities are the things that the database will
  contain a representation of.
• Entities can be anything people, places, events,
  physical objects, or concepts.
• All the entities with the same characteristics
  can be collectively called an entity type.
• Relationships describe the way entities are
  connected to each other.

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Relationships

• one to one relationships connect one entity to
  one other entity.
• one to many relationships connect one entity to
  one or more other entities.
• many to many relationships connect many entities
  to many other entities.

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Data

• The field is the basic unit of data in a
  database. A field stores a single piece of
  information of a particular data type.
• Fields are combined to form records. A record
  matches an entity.
• A set of records with the same fields are
  collected together in a table

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Historical Uses for a Database

• To store and organise large amounts of
  information automatically.
• To provide easy access to the information
  contained in the original source.
• An environment for manipulating (changing and
  adjusting) the source.
• To search/filter/summarise complex information
  quickly.

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Historical Database Example
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Historical Databases

• Technical decisions are often the least
  important.
• Historians work with information they do not
  control.
• incomplete, poorly structured information of
  varying quality.
• A historical source based database is a
  representation of the primary source, but it is
  not an exact replica of the primary resource.
• Some information may be left out.
• some extra information may be included.
• A historical source based database mixes elements
  of a primary source with elements of a secondary
  source.

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The Three Layer Model
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Three Layer Design Examples
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Simple Design Hints

• Make sure the smallest unit of data matches the
  smallest unit of analysis.
• If you want to look at people by last name then
  have separate first and last name fields, not
  just a name field.
• Dont mix data types
• separate numbers and words.
• Document everything you, either in the database
  or with the database.
• Data entry, data standardisation and coding, data
  transformations, limits of data etc.
• Keep information that tracks the origin and
  history of the database.
• Add information, dont delete information.

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Further Information

• Starting Out
• Michael J. Hernandez, Database Design for Mere
  Mortals A Hands-On Guide to Relational Database
  Design, Addison-Wesley, 1997.
• Database Central, http//databasecentral.com/
• History Data Service, http//hds.essex.ac.uk/
• The Classics
• Charles Harvey Jon Press, Databases in
  Historical Research, Macmillan Press, 1996.
• C. J. Date, An Introduction to Database Systems,
  Addison-Wesley, 1999 (7th ed.)