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Following the discussion between Delft Hydraulics and CEH & Wallingford Software on Friday 2 May 2003 in Wallingford on providing an enumeration of quality flags as a part of the SIS, a proposed quality flag enumeration is given in the table below. As described in the timeseries XML schemas provided we have made allowance for a single quality flag. This is contrary to the EA XML interchange formats which provide for three separate quality flags. A single flag seems more appropriate to the level of communication we are dealing with and should avoid ambiguity. The flags are single byte values and are incorporated in the XML Schema for time series. Quality flags are provided for each data point.

 

Quality flags are constructed on a philosophy of two qualifiers. The first described the origin of the data and the second the quality.

 

Possible origins of data are:

 

1.       Original: This entails the data value is the original value. It has not been amended by NFFS

2.       Completed: This entails the original value was missing and was replaced by a non-missing value.

3.       Corrected: This entails the original value was replaced with another non-missing value.

 

Possible qualifiers are:

 

4.       Reliable: Data is reliable and valid

5.       Doubtful: The validity of the data value is uncertain

6.       Unreliable: The data value is unreliable and cannot be used.

 

Following this specification, the table below gives an overview of quality flag enumerations

 

Table D.1               Enumeration of quality flags

 

Enumeration

Description

0

Original/Reliable
The data value is the original value retrieved from an external source and it successfully passes all validation criteria set.

1

Corrected/Reliable
The original value was removed and corrected. Correction may be through interpolation or manual editing.

2

Completed/Reliable
Original value was missing. Value has been filled in through interpolation, transformation (e.g. stage discharge) or a model.

3

Original/Doubtful
Observed value retrieved from external data source. Value is valid, but marked as suspect due to soft validation limits being exceeded.

4

Corrected/Doubtful
The original value was removed and corrected. However, the corrected value is doubtful due to validation limits.

5

Completed/Doubtful
Original value was missing. Value has been filled in as above, but resulting value is doubtful due to limits in transformation/interpolation or input value used for transformation being doubtful.

6

Missing/Unreliable
Observed value retrieved from external data source. Value is invalid due to validation limits set. Value is removed

7

Corrected/Unreliable
The original value was removed and corrected. However, corrected value is unreliable and is removed.

8

Completed/Unreliable
Original value was missing. Value has been filled in as above, but resulting value is unreliable and is removed.

9

Missing value in originally observed series. Note this is a special form of  both Original/Unreliable and Original/Reliable.

 Notes:

  • No difference is made between historic and forecast data. This is not considered a quality flag. The data model of NFFS is constructed such that this difference is inherent to the data type definition.
  • External sources may either be an actual external source, a forecasting module or a transformation. The convention in NFFS the definition of data series parameter types identifies the data source. 
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