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 Major goal: supporting interactive and data-fed animations, such as pie charts and change their shapes Current: JPG and GIF and PNG raster images New: Canvas – to create bit mapped images and animation New: SVG (scalable vector graphics) – vector graphics in an XML syntax, with color and gradient color But right now there are few apps that produce these animations Goal is a standard for apps that produce interactive and non- interactive animation Goal: to get images to appear identical in different browsers and varying sizes, in particular on small devices Goal: to get animations to appear identical in different browsers and on small devices 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 and applications Video Audio Logos: with SVG Charts: with Canvas 9

Managing local data Long a problem with standard HTML Previously, we had to use cookies and/or Ajax code In HTML5, there is a “LocalStorage” In use already in Gmail for Iphones It makes use of SQLite But an SQL database is not part of the standard; it just makes it possible to plug one in 10

Video: a special focus Video is embedded in many sites now Streaming rates are fast enough for most people to play even large videos on the Web Two supported formats MPEG4 Ogg (like MPEG4, can handle small video all the way to HD) Audio Ogg is also supported – but not MP3 The goal is to remove the highly varying ways in which browsers will manage video Before HTML5 it was difficult to put video in a form that all browsers would play You are no longer expected to test to see what plugin exists in the user’s browser But Ogg support is not broad yet 11

Style sheets: CSS3 (not strictly tied to HTML5) Some advancements, such as embedding specific fonts in pages, and not hoping your “font family” is supported well enough on your user’s page Better and finer grained support of font color Supports finer grained control of fonts on pages Better multi-column support Easier and more fine grained control of position on web pages Better control of graphics color Two forms of animation: Transitions: time, easing in and easing out, motion curves (Bezier) Transforms: more advanced movement, like bouncing Better support for mobile devices 12