Data, schemas and Applications IFIEKG-20-3

Staff Chris Wallace – module leader and tutor Praminda Calib-Soley - tutor David Wyatt – tutor

Assessment 50% exam 50% coursework –Term 1 – well-defined group project using PHP and SQL –Term 2 – open individual project using XML Project-based – work on the coursework to trigger needs for teaching

Themes (see handout) Under the hood Design decisions Data structures Multimedia Interactivity Applications Questions?

Technology 1 PHP/MySQL –You need to learn enough about PHP to be able to develop simple scripts to interface between the user’s browser and the data store. –You need to learn enough about SQL to do simple queries and updates from a script. There are range of resources, some written by me, many on the Web –Books: Welling and Thomson, PHP and MySQL Web Development (4 th ed), Sams Ullman, PHP and MySQL, Peachpit Press –Example code for the MMS photo album.

Example MMS picture log –Registered members can send photos from a mobile phone via to –Photos arrive as a MIME document which needs decoding to extract the useful bits (an open source script)MIME –The originating mobile phone number is used to identify the member, the title becomes the photo title –The photo is added to the database –A viewer can select any member and view their accumulated photos.

Data Modelling Data is stored in many different physical ways –in files with complex structure, in databases, in XML documents, in filestores. –Compressed –Optimised for access in a particular way We need some way of describing the data which ignores (abstracts from) these details of physical storage. –One common technique is Entity-Attribute- Relationship diagrams. (often called just ER models)

EAR model This modelling language allows a very small vocabulary: Just as English has nouns, verbs, adjectives, pronouns.., EAR models have only 3 central concepts –Attribute – a simple, atomic data item like a date, a name, a number [also called Property or Field] –Entity – a group of attributes which are all related to the same thing [also called Entity Type or Class] –Relationship – a relationship between Entities.

MMS Photo : EAR diagram Entity Attribute Relationship Primary key Data Type Each Member has created many Photos Each Photo created by exactly one Member Diagram generated by QSEE

Data Modelling hints Modelling in a formal language isn’t easy – its like learning and using a new language. Your fluency with the language will improve with use. There is no ‘correct’ model but there are ‘incorrect’ models. The language is incomplete – you can say all you might want to describe in the formal language, so you will have to add informal descriptions as well.