Re: Units of Measurement in the Database Model

From: James <jraustin1_at_hotmail.com>
Date: 30 May 2002 13:39:45 -0700
Message-ID: <a6e74506.0205301239.68fb0b3d@posting.google.com>

> From original poster:
> How should the database be organized in regards to measurements recorded,
> and the units of measurement (UOM) used to record them?

I am not suggesting to use an oodb solution but it may shed light on the appropriate rdb solution.

In XDb each "value" is actually an object. Each "value" (ie 130, 180) is an instance of a class (ie Weight) or its descendant sub classes. The base class can define a default UOM as a static property. A static (as opposed to a virtual) property does not propagate with instances of Weight. Any sub class or instance can override the default by having a UOM property.

Implementation would be:

Classes

---

UOM Weight
  .UOM - lb // Static property of weight

Instances

---

UomInstsFldr
  lb
  kg   

WeightInstsFldr
  130 // Inherits UOM = lb as defined in class   180
    .UOM - kg // Overrides default UOM defined in Class

Thus,
130.Prop_get(UOM) returns 'lb'. 130 inherits the default UOM defined in its class.
180.Prop_get(UOM) returns 'kg'. 180's UOM overrides that defined in its class.

It is also possible to define as such

Classes

---

System

UOM
  .System = Unknown

Instances

---

System
  Unknown
  English
  Metric

UomFldr
  lb
   .System = English
  kg
   .System = Metric

Thus,
(130.Prop_get(UOM)).Prop_get(System) returns 'English' (180.Prop_get(UOM)).Prop_get(System) returns 'Metric'

Above implementation is described more visually at www.xdb1.com/Basics/UOM.asp

Also see www.xdb1.com/Dev/API/Obj/Prop_get.asp & ww.xdb1.com/Basics/Property.asp Received on Thu May 30 2002 - 15:39:45 CDT