The E/R model, triggers, HTML5 Reminder … next Tuesday is the first exam. 1

E/R A design front end for relational databases, not as an independent model Intended to have a visual syntax As opposed to “semantic” models that were intended as alternatives to the relational model Knowledge representation to semantic models Another alternative: object-oriented models Object-oriented programming languages to object-oriented data models to object-relational data models At a higher perspective: there is a long spectrum of data structuring, and our models only handle a small part 2

E/R Entities Relationships Attributes Roles Cardinality constraints Type hierarchies Exclusive relationships 3

Mapping to relational schemas Both entities and relationships turn into tables Attributes are attributes Constraints lead to multiple tupes or set-valued atts 4

Triggers ON event IF precondition THEN action Used for constraints and “business rules” and monitoring Triggers are “activated” Consideration: immediately or deferred to commit time Before, after, instead of triggers Row level versus table level triggers Can refer to old and new tuples On delete: cascade or turn null Issue: chain reactions Issue: tangled, non-declarative semantics 5

HTML5 Web 2.0/3.0 versus the “semantic web” New elements, largely to support advanced media New elements for structuring pages, as well 6

Illustrations and rendering Current: JPG and GIF and PNG raster images New: Canvas – to create bit mapped imags New: SVG (scalable vector graphics) – vector graphics in an XML syntax, with color and gradient color 7

CANVAS An alternative to Flash animation Displacing SMIL Creates bit mapped images (not vector graphics, as with SVG) Can build lines, rectangles, curves Curves: Bezier, arcs, and others Colors 8

Other media Video Audio Logos: with SVG Charts: with Canvas 9