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How to create an AsciiReader
The input for model systems is often contained in simple ASCII files. Wrapping these files allows you to make the data available to OpenMI-compliant systems. For example, you can wrap the output file from one component so that it serves as the input for another component. When such a file is wrapped, it can be accessed in the same way as any other OpenMI component. The wrapped output file makes it easy to test the OpenMI component that uses the file as input. It will also be possible to run the component using the data without having to run the delivering component.
To be OpenMI-compliant, a component needs to implement two interfaces: the IPublisher and ILinkableComponent interfaces. Therefore the ASCII reader needs to implement these interfaces. As with model systems, this can be done by inheriting from 
...
 Oatc.OpenMI.Sdk.Wrapper.LinkableEngine 
...
 and 
...
 implementing 
...
 specific 
...
 methods.
...
The 
...
 difference 
...
 between 
...
 the 
...
 wrapping 
...
 of 
...
 ASCII 
...
 files 
...
 and 
...
 the 
...
 approach 
...
 used 
...
 for 
...
 model 
...
 components 
...
 lies 
...
 in 
...
 the 
...
 implementation 
...
 of 
...
 the 
...
 ExchangeItems 
...
 (GetOutputExchangeItem) 
...
 and 
...
 the 
...
 GetValues 
...
 call. 
...
 In 
...
 the 
...
 case 
...
 of 
...
 a 
...
 model 
...
 component, 
...
 the 
...
 ExchangeItems 
...
 will 
...
 usually 
...
 be 
...
 provided 
...
 by 
...
 a 
...
 populated 
...
 model 
...
 kernel. 
...
 When 
...
 wrapping 
...
 an 
...
 ASCII 
...
 file, 
...
 the 
...
 information 
...
 about 
...
 possible 
...
 ExchangeItems 
...
 must 
...
 be 
...
 contained 
...
 in 
...
 the 
...
 ASCII 
...
 file 
...
 itself.
...

 Figure 
...
 1 
...
 is 
...
 an 
...
 example 
...
 of 
...
 an 
...
 ASCII 
...
 file 
...
 (
...
get 
...
 file
...
; 
...
 there 
...
 are 
...
 four 
...
 lines 
...
 of 
...
 comments, 
...
 followed 
...
 by 
...
 a 
...
 line 
...
 specifying 
...
 the 
...
 quantity 
...
 and 
...
 another 
...
 containing 
...
 the 
...
 three 
...
 locations. 
 Code Block
 

{code}
// Lines starting with // are comment
// The first uncommented line defines the quantity
// The second uncommented line defines the locations
// All next lines consist of a timestamp and values of the quantity for each location
"Flow"
"Loc1";"Loc2";"Loc3"
"2005-01-01 00:00";"15.4";"18.2";"22.4"
"2005-01-01 03:00";"15.3";"18.5";"22.5"
"2005-01-01 06:00";"15.4";"18.9";"22.4"
"2005-01-01 09:00";"15.2";"19.0";"22.6"
"2005-01-01 12:00";"15.1";"18.8";"22.7"
"2005-01-01 15:00";"14.8";"18.6";"22.9"
"2005-01-01 18:00";"14.7";"18.4";"23.4"
"2005-01-01 21:00";"14.7";"18.2";"23.8"
"2005-01-02 00:00";"14.6";"18.2";"23.9"
"2005-01-02 03:00";"14.1";"18.1";"24.0"
"2005-01-02 06:00";"13.8";"18.2";"23.5"
"2005-01-02 09:00";"13.9";"18.0";"23.6"
"2005-01-02 12:00";"13.6";"17.8";"23.5"
"2005-01-02 15:00";"13.2";"17.3";"23.3"
"2005-01-02 18:00";"12.8";"17.4";"23.2"
"2005-01-02 21:00";"12.7";"17.2";"23.1"
"2005-01-03 00:00";"12.6";"17.2";"22.9"
"2005-01-03 03:00";"12.1";"16.8";"22.7"
"2005-01-03 06:00";"12.2";"16.6";"22.5"
"2005-01-03 09:00";"11.4";"16.5";"22.4"
"2005-01-03 12:00";"11.6";"16.4";"22.2"
"2005-01-03 15:00";"11.7";"16.3";"21.8"
"2005-01-03 18:00";"11.6";"16.0";"21.5"
"2005-01-03 21:00";"11.2";"15.8";"21.4"
"2005-01-04 00:00";"11.0";"15.6";"21.3"
{code}

Figure 
...
 1 
...
 An 
...
 example 
...
 ASCII 
...
 file
...
This 
...
 information 
...
 defines 
...
 the 
...
 possible 
...
 OutputExchangeItems.
...
The 
...
 OutputExchangeItems 
...
 could 
...
 look 
...
 like 
...
 the 
...
 following:
 Code Block
OutputExchangeItem[0] = { "Flow", "Loc1"}
OutputExchangeItem[1] = { "Flow", "Loc2"}
OutputExchangeItem[2] = { "Flow", "Loc3"}


Implementing 
...
 an 
...
 OpenMI-compatible 
...
 linkable 
...
 component 
...
 that 
...
 uses 
...
 this 
...
 ASCII 
...
 file 
...
 as 
...
 input 
...
 and 
...
 makes 
...
 the 
...
 contents 
...
 of 
...
 the 
...
 file 
...
 available 
...
 through 
...
 OutputExchangeItems 
...
 requires 
...
 the 
...
 following 
...
 steps:
...
  • Start 
...
  •  developing 
...
  •  the 
...
  •  component 
...
  •  by 
...
  •  implementing 
...
  •  org.OpenMI.Utilities.Wrapper.LinkableEngine.
...
  • Write 
...
  •  code 
...
  •  for 
...
  •  methods 
...
  •  such 
...
  •  as 
...
  •  Initialize, 
...
  •  Finalize, 
...
  •  GetModelID 
...
  •  and 
...
  •  GetModelDescription.
...
  • Write 
...
  •  code 
...
  •  for 
...
  •  the 
...
  •  SetValues, 
...
  •  GetInputExchangeItem 
...
  •  and 
...
  •  GetInputExchangeItemCount 
...
  •  methods; 
...
  •  these 
...
  •  methods 
...
  •  are 
...
  •  empty 
...
  •  because 
...
  •  the 
...
  •  ASCII 
...
  •  reader 
...
  •  does 
...
  •  not 
...
  •  accept 
...
  •  data.
...
  • Write 
...
  •  code 
...
  •  for 
...
  •  the 
...
  •  GetOutputExchangeItem 
...
  •  method; 
...
  •  make 
...
  •  sure 
...
  •  the 
...
  •  ASCII 
...
  •  file 
...
  •  is 
...
  •  read, 
...
  •  the 
...
  •  ExchangeItems 
...
  •  are 
...
  •  extracted 
...
  •  from 
...
  •  the 
...
  •  file 
...
  •  and 
...
  •  the 
...
  •  OutputExchangeItems 
...
  •  are 
...
  •  defined.
...
  • Write 
...
  •  code 
...
  •  for 
...
  •  the 
...
  •  GetValues 
...
  •  method; 
...
  •  this 
...
  •  should 
...
  •  extract 
...
  •  the 
...
  •  correct 
...
  •  data 
...
  •  for 
...
  •  the 
...
  •  requested 
...
  •  timestamp/ExchangeItem 
...
  •  combination 
...
  •  from 
...
  •  the 
...
  •  ASCII 
...
  •  file.
...
Prototype 
...
 code 
...
 for 
...
 GetOutputExchangeItem 
...
 is 
...
 given 
...
 in 
...
 Figure 
...
 2.


{
 Code Block
}
public IOutputExchangeItem GetOutputExchangeItem(int outputExchangeItemIndex)
{
return _output;
}

private void ReadFile() 
{
	StreamReader reader = new StreamReader(_inputFile);
	bool quantityRead = false;
	bool elementsRead = false;
	_timeStamps.Clear();
	_elementValues.Clear();

	string line;
	while ((line = reader.ReadLine()) != null) 
	{
		if (line.StartsWith("//")) 
		{
			// ignore
		}
		else if (!quantityRead) 
		{
			_quantity = new Quantity(line.Trim(' ', '"'));
			_output = new OutputExchangeItem();
			_output.Quantity = _quantity;
			quantityRead = true;
		}
		else if (!elementsRead) 
		{
			string[] elements = line.Split(';');
			_elementSet = new ElementSet();
			_elementSet.ID = "File Contents";

			_output.ElementSet = _elementSet;

			for (int i = 0; i < elements.Length; i++) 
			{
				_elementSet.AddElement (new Element(elements[i].Trim('"')));
			}
			elementsRead = true;
		}
		else 
		{
			string[] values = line.Split(';');
			DateTime timestamp = Convert.ToDateTime (values[0].Trim('"'), _culture);
			double modifiedJulianDateTime = CalendarConverter.Gregorian2ModifiedJulian(timestamp);

			double[] locationValues = new double[values.Length - 1];
			for (int i = 1; i < values.Length; i++) 
			{
				locationValues[i - 1] = Convert.ToDouble (values[i].Trim('"'), _culture);
			}
			_timeStamps.Add (modifiedJulianDateTime);
			_elementValues.Add (locationValues);
		}
	}
}
{code}

Figure 
...
 2 
...
 Code 
...
 for 
...
 GetOutputExchangeItem
...
A 
...
 prototype 
...
 of 
...
 the 
...
 GetValues 
...
 method 
...
 is 
...
 shown 
...
 in 
...
 Figure 
...
 3.


{
 Code Block
}
public IValueSet GetValues(ITime time, string linkID)
{
	ILink outgoingLink = (Link) _links[linkID];

	if (outgoingLink == null)
	{
		throw new Exception ("Unknown link or quantity");
	}

	if (time is TimeStamp) 
	{
		TimeStamp timestamp = (TimeStamp) time;

		double[] results;
		for (int i = 0; i < _timeStamps.Count; i++) 
		{
			if ( (double)_timeStamps[i] + _delta > timestamp.ModifiedJulianDay) 
			{
				results = (double[]) _elementValues[i];
				return new ScalarSet(results);
			}
		}

		throw new Exception ("No appropriate values found");
	}

	throw new Exception ("Time should be of type TimeStamp");
}
{code}

Figure 
...
 3 
...
 Example 
...
 GetValues 
...
 method
...