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 Address1 Address2 Address3 TownID Postcode LocationPhysID LastDate Etc. Town Name TownID LastDate

Relationships (model) Agent [AgentPers] Forename Surname Dates … AgentID … Administers AccessOpenHours … AdministersID … AgentID LocationID Location [LocationPhys] Address1 Address2 Address3 TownID … 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, CAIRNS, Cultural portal