Back to the Data Model
The Requirements have been established as follows.
The Project is to produce a complete Enhanced Entity Relationship (EER) Diagram, including a
complete list of all entities, their attributes including all primary/foreign keys.
The Things of Interest
Work Completion Certificate
The Client is PDL Property Developers Ltd, who buy, renovate and re-sell properties.
All of PDL’s properties are either houses, bungalows, flats or maisonettes in and around the London area.
PDL has a strict policy of only buying properties from licensed auctions where they know properties are
available at low prices.
PDL does not rent its properties, it only buys repairs and resells them.
PDL may purchase as many as six or seven properties at a single auction.
Once purchased, each property is fully inspected by PDL and a list of repairs required for that
property is made by an PDL surveyor.
So as to minimise costs PDL has a list of standard repairs that it can perform, each with an approximate cost
and time constraint.
A given property may need no repairs whereas another property may need several repairs. With this information, once
a property has been assessed for repairs, the cost and time needed to complete all necessary work can be estimated.
PDL works with several people in the renovation process: They keep a list of skilled Workers who may
be called upon to come in and perform specific repairs on each property. However it has a strict policy of
assigning only one skilled worker to perform each specific repair on a particular property. In this way the
PDL surveyor can accurately monitor which workers are performing which repairs, and assess whether
the job is done within time, budget and quality requirements.
The re-sale value of a property is calculated by adding the repair costs to the price paid at auction, then a commission
of between 5% and 20% is added to ensure that a reasonable profit is made when selling the property.
On completion of all required repairs each property is re-inspected by a surveyor and if all work is
done to the required standard, a certificate of work completion is issued for the property.
If not, the worker hired for any sub-standard repair will be recalled to complete the work to PDL’s
satisfaction at no extra cost.
The surveyor is gaining a reputation for being a source of regular work for skilled locals in the
building trade and competition to obtain work from them is becoming quite intense.
When a repair is completed and inspected as being satisfactory a fixed rate single cash payment is made to the
skilled worker for the repair job.
Having received a work completion certificate each property is then advertised for sale on PDL’s web site.
Initially one and possibly more web Adverts are placed for each property. In circumstances where PDL has
properties that are on the same street or sometimes within the same housing development/estate a single web advert
may be placed advertising multiple properties.
PDL only sells its properties via its own web site (run by a small team of PDL Salespeople) and does
not use external estate agents. When a Buyer is found who wants to purchase an PDL property a Sales Contract
is made by an PDL salesperson (between the Buyer and PDL) specifically for a given
On the day the contract is drawn up the buyer must provide PDL with a bankers draft for 10%
of the property re-sale value.
The remaining 90% balance must be paid by one or more electronic money
transfers to PDL within 28 days of the contract date. If this is done successfully the buyer takes
possession of the property with a copy of the Work Completion Certificate, the property’s web Advert is
then taken offline.
If the buyer does not complete the sale within 28 days PDL keeps the deposit paid, the sale contract is
void, and the property remains on sale for any prospective buyers. If a buyer fails to complete on 3
occasions (on separate properties) PDL makes a note on the buyers record and in future such buyers
would have to pay the full amount due on the day the sale contract is drawn up.
2nd. December 2007