Specification Processes	Top

Overview

A "Specification" is a set of numerical limits and rules against which entered data are checked to provide an indication of the "quality" of entered data. Two methodologies are available to check data against a Specification:

Spec Limit Checking is conducted at the Data Item level by comparing entered data to a set of Specification Limits, each of which indicates a "Spec Condition". When the data value falls with a Specification Limit, the corresponding Spec Condition is reported.

Data Entry					Items Evaluated During Spec Limit Checking
Sample	Data Set	Parameter	Data Value		Specification Limit	Spec Condition when Data Value is withing Specification Limit
Sample-001	Metals	Au	7.2		Au < 10	Out of Spec
		Al	41.4		Al > 30	Out of Spec
		Ni	12.6		10 ≤ Ni ≤ 15	Warning
		Fe	27.9		30 ≥ Fe > 25	Warning
		Pt	19.5		15 ≤ Pt ≤ 25	In Spec

Spec SDI Checking begins by performing Spec Limit Checking as shown above. Next, all Spec Conditions generated for the SDI are used to analyze one or more Specification Rules. The Specification Rules determine the "SDI Condition", which indicates the quality of all data entered for the SDI.

Data Entry					Items Evaluated During Spec SDI Checking
Sample	Data Set	Parameter	Data Value		Specification Limit	Spec Condition	Specification Rules	SDI Condition
Sample-001	Metals	Au	7.2		Au < 10	Out of Spec	If the Spec Condition of any Parameter is "Out of Spec", set the SDI Condition to "Fail". Otherwise, set the SDI Condition to "Pass".	Fail
		Al	41.4		Al > 30	Out of Spec
		Ni	12.6		10 ≤ Ni ≤ 15	Warning
		Fe	27.9		30 ≥ Fe > 25	Warning
		Pt	19.5		15 ≤ Pt ≤ 25	In Spec

Spec Limit Checking Process	Top

This example shows how Spec Limit Checking is conducted. At the Data Item level, entered data are compared to the numerical Specification Limits. When entered data falls within these limits, the "Specification Limit Type" defines a "Spec Condition", which is reported to indicate where the data falls (such as "Out of Spec" or "In Spec"). 

To summarize, here is what you must do prior to entering data for the SDI:

Spec SDI Checking Process	Top

After the Spec Limit Checking process has determined a Spec Condition for each Parameter, the check can be further extended by applying "Specification Rules". These are conditional statements that use the Spec Conditions of individual Parameters to determine an "SDI Condition", thus providing an indication of all data entered for an SDI.

There are currently two types of engines that process Specification Rules:

As an example, consider entering a Data Value for each of two Parameters (Al and Fe).  Both Parameters belong to the Metals Parameter List, a single instance (Data Set) of which is assigned to SDI_001.  You want to determine an SDI Condition to get an indication of all data for the SDI.

The illustration above shows how the entire process works.  The table below shows how you could define these Specification Rules under the Rules tab of the Specification Maintenance Page.

¹ The Specification Maintenance Page uses the term Spec Condition to refer to the SDI Condition.  You define SDI Conditions the same way you define Spec Conditions, i.e., they are Reference Values you define in the Spec Condition Reference Type. 

During execution:

The above example assesses individual Spec Conditions for each Parameter as follows:

As an example, suppose you set your Specification Limits to indicate the following Spec Conditions:

When you enter data, and as you change it, the two Rules in the previous example should yield the following results:

Specification Rules do nothing more and nothing less than you tell them.  You must account for all possibilities that can occur during a Data Entry session.  In general, check for the following occurrences in the order specified:

After these rudimentary checks, you can perform more specific or advanced checking if required.

These are easier to use than Expression-Based Rules.

Recall from the previous discussions that, when using Specification Rules:

Banded Rules cover the most basic case. Multiple "bands" can be specified, with the final band being the default condition. Here's an example:

Structured Rules let you create multiple rules, each defining a series of conditions according to fixed grammar. The Rules Engine processes each rule individually, stopping after it processes a rule that returns true. Example:

Unlike Banded Rules, a default condition is not necessary. However, one can be specified as shown in the above example.

Additional Information	Top

Linking Specifications to other SDCs

The Specification SDC (SpecSDC) is a System SDC, thereby letting you add columns and link it to any other SDC.  You can relate a Specification to SDIs by creating an SDC Link from a Specification column to the relevant SDC.

The two models below show the relationship. The first generic model shows how SDIs "own" a Specification.  The second model is an example of how Motor Oil can be checked against the Viscosity Spec, which has the columns Product, Customer, and Grade.  Using three SDC Links, the Viscosity Spec applies to SDIs in the SDCs Product, Customer, and Grade.