From model to service: relational databases and SCONE

Presentation to CDLR staff on Wed 5 Feb 2003

By Gordon Dunsire

Overview

• From theory to practice

• A bit about collection level description

• A bit about relational database design

• A bit about entity-relationship models

• Not necessarily in that order!

• But using SCONE as a case-study

Implementation stages

• Entity-relationship model

• Attribute sets

• Entities & relationships map to relational database tables

• Attributes map to fields (columns) in table

• Tables related using standard rdbms structures

• Service data retrieved using SQL

Entity-Relationship model

• Defines entities (things) and relationships between them

• Entity-Relationship-Entity syntax

• Defines attributes (pieces of information) common to each entity and relationship

• SCONE is based on a model developed by Michael Heaney for UKOLN

Heaney’s Analytic Model

Attribute sets

• Entity: Location (physical repository)– Place; Identifier

• Entity: Agent:Collector (person)– Name; Date; Biography

• Relationship: Collects– Legal status; Accrual policy

• Relationship: Administers– Access conditions

Implementation in RDBMS

• Map entities and relationships to tables– Entity Location (physical repository) maps to

table LocationPhys– Relationship Collects maps to table Collects

• Map attribute sets to fields in each table– Decomposition to finer detail data elements

where appropriate• E.g. Location – place decomposes to building

name, address, town, region, postcode, etc.

Example: LocationPhys

• Table fields from attributes– Address1– Address2– Address3– Postcode

• Plus fields from “experience tells me” attributes– Notes

Example: LocationPhys

• Plus fields for administrative metadata– LastDate

• Plus fields for RDBMS structure– LocationPhysID (primary key)– TownID (secondary, foreign key)

• Maps attribute Town to a lookup table (Town treated as an entity) matched by keys

Relational databases

LocationPhys

Address1Address2Address3TownID

PostcodeLocationPhysID

LastDateEtc.

Town

NameTownID

LastDate

Relationships (model)

Agent[AgentPers]

ForenameSurname

Dates…

AgentID…

Administers

AccessOpenHours…

AdministersID…

AgentIDLocationID

Location[LocationPhys]

Address1Address2Address3TownID

…LocationID

…

Terminological inexactitudes

• Relationships (model) are NOT the same as relationships (RDBMS)– But can often appear so!

• Relationship (m) requires its own table (mostly); relationship (r) is the link between tables– Can sometimes simplify so relationship (m) is

implicitly defined by relationship (r), but NOT if relationship (m) has its own attributes

Assembling the record

• Use Structured Query Language (SQL) to request fields from related tables matching specified criteria

• E.g. to get location town and postcode:– SELECT Town.Name,

LocationPhys.Postcode FROM LocationPhys INNER JOIN Town on Town.TownID=LocationPhys.TownID WHERE LocationPhys.LocationPhysID=23

SCONE Service

• Web page design and content by DreamWeaver

• RDBMS data added to page content dynamically by ColdFusion– Fully integrated environment with DW– SQL scripts– Data processing (program flow) scripts

• Data stored in SQL Server

Views

• SCONE data retrieved in different ways for different purposes using SQL– Data is stored once, used many times– Data updates are immediately visible– Data updated once, visible in many places

• Single RDBMS supports multiple, overlapping services:– SCONE, SCAMP, SLIR (SWOP, ESH), RCO,

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