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Maintenance Contracts
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Boschendal, South Africa
Design Notes :-
I have shown the 'Third_Party_Companies' Entity as being either a Supplier or a Maintenance Contractor.
This makes the Database more readable and easier to use, at the expense of generality.
In practice, a Supplier is also likely to provide Maintenance, and therefore be both a Supplier and a Maintenance Contractor.
However, for an alternative design with more generality I have defined an Entity called 'Ref_Company_Types'.
I have not used it and so it is not joined in a Relationship to any other Entity.
If this Reference Data Entity were to be used it would be necessary, of course, to add a 'company_type_code' to the 'Third_Party_Companies' Entity, and then you could either remove or leave the maintenance_contractor_yn and supplier_yn attributes.
This Page defines the Requirements for a Database for Machine Maintenance.
It contains four Sections :
1. Things of Interest
2. How these Things are related
3. Characteristics of these Things
4. User Scenarios

  1. The Things of Interest include :-
    • Component Machine Parts, (this is a List of all Component Parts in all Machines).
    • Contracts
    • Engineer Visits
    • Faults, recorded in a Fault Log.
    • Machines
    • Machine Parts, (these are the specific Parts in a particular Machine).
    • Maintenance Contracts
    • Maintenance Engineers
    • Parts
    • Machine Parts, (these are the specific Parts in a particular Machine).
    • Parts - these are the Component Parts.
    • Part Faults, (these are the Faults that can occur with a specific Part).
    • Skills
    • Staff
    • Third Party Companies

  2. How are these Things related :-
    • A Fault will always be associated with one Machine, and at least one Part of that Machine.
    • A Machine can have one or many Parts.
    • A Part can be associated with one or many Faults.
    • A Part can be associated with one or many Faults.
    • A Member can belong to one and only one Ministry.
    • A Member can have zero, one or many Skills.
    • A Ministry can arrange zero, one or many Activities.
    • Staff are associated with one or many Ministries.
    • Staff can have zero, one or many Skills.

  3. Characteristics of these Things :-
    • A Contract has :-
    • A Sart Date and an End Date.

  4. User Scenarios :-

Barry Williams
20th. December 2002
Principal Consultant
Database Answers

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