SemanticValue Class

SemanticValue is the primary object that implements the semantic technology in System.Speech. Semantic interpretation allows grammars to define rules for use by a recognition engine to correctly interpret audio input. Semantic interpretation also enables recognition engines to organize their results so that they can be more easily processed, rather than returning only recognized words and sequences of words.

For example, the recognition engine output "Change background to red" would have to be parsed and interpreted by an application before it could be acted upon. A Grammar object can specify a semantic interpretation to make processing clearer by specifying that the phrase has two semantic substructures, one for selecting background or foreground (represented by the text "background"), and the other for selecting color (represented by the text "red").

System.Speech represents the semantics of a recognition operation in a tree of SemanticValue objects.

Each SemanticValue instance includes the following:

• An Object, accessed by means of the Value property, used to key the instance of the SemanticValue.

• A measure of the accuracy of semantic parsing, returned by the Confidence property.

• A collection of name/value pairs ([T:System.Collections.Generic.KeyValuePair(TKey,TValue)]) of child objects, which are also SemanticValue instances. Child nodes are accessible through the SemanticValue implementation of [T:System.Collection.Generic.IDictionaryIDictionary(TKey,TValue)] using a string lookup key and a SemanticValue instance, as in the following example.

  C#

  Copy

  foreach (KeyValuePair<String, SemanticValue> child in semantics) 
  {
    Utils.CreateSemanticsTreeNodes(semanticsNode.Nodes, child.Value, child.Key);
  }
  

Recognition engines based on System.Speech provide valid instances of SemanticValue for all output from recognition, even for phrases with no explicit semantic structure.

The SemanticValue instance for a phrase is obtained using the Semantics property on the RecognizedPhrase object (or objects that inherit from it, such as RecognitionResult).

SemanticValue objects obtained for recognized phrases without semantic structure are characterized by:

• The lack of children (Count is 0).

• The Value property is null.

• An artificial semantic confidence level of 1.0 (returned by Confidence).

Typically, applications create SemanticValue instances indirectly, adding them to Grammar objects by using SemanticResultValue and SemanticResultKey instances, in conjunction with Choices and GrammarBuilder objects.

Direct construction of a SemanticValue instance is useful during the creation of strongly-typed grammars.

SemanticValue implements the [T:System.Collection.Generic.IDictionary(TKey,TValue)], [T:System.Collections.Generic.ICollection(T)], and [T:System.Collections.Generic.IEnumerable(T)] interfaces.

The following example shows a handler for a SpeechRecognized event designed to handle commands to change foreground and background color.

The handler identifies recognized phrases that have no underlying semantic structure by detecting a Count of zero and a Value of null. This recognition output is then processed directly by parsing the raw text.

In other cases, the handler uses keys to obtain the RGB components of a color name, to determine whether the command will change the foreground or background, or to indicate that no valid key was found.

newGrammar.SpeechRecognized +=
  delegate(object sender, SpeechRecognizedEventArgs eventArgs) 
  {

    // Retrieve the value of the semantic property.
    bool changeBackGround = true;
    string errorString = "";
    SemanticValue semantics = eventArgs.Result.Semantics;

    Color newColor = Color.Empty;
    
    try 
    {
      if (semantics.Count == 0 && semantics.Value==null)
      {
        // Signifies recognition by a grammar with no semantics.
        // Parse the string, assuming that the last word is color,
        // and search for “background” or “foreground” in the input.
        if (eventArgs.Result.Text.Contains("foreground")) 
        {
          changeBackGround = false;
        }
        string cName = eventArgs.Result.Words[eventArgs.Result.Words.Count - 1].Text;
        newColor = Color.FromName(cName);
        
      }
      else if (semantics.ContainsKey("colorStringList") ^ semantics.ContainsKey("colorRGBValueList")) 
      {

        // Determine whether to change background or foreground.
        if (semantics.ContainsKey("applyChgToBackground")) 
        {
          changeBackGround = semantics["applyChgToBackground"].Value is bool;
        }

        // Get the RGB color value.
        if (semantics.ContainsKey("colorStringList")) 
        {
          newColor = Color.FromName((string)semantics["colorStringList"].Value);
        }
        if (semantics.ContainsKey("colorRGBValueList")) 
        {
          newColor = System.Drawing.Color.FromArgb((int)semantics["colorRGBValueList"].Value);
        }
      }
      else 
      {

        // Throw an exception if the semantics do not contain the keys we
        // support.
        throw(new Exception("Unsupported semantics keys found."));
      }
    }

    catch (Exception exp) 
    {
      MessageBox.Show(String.Format("Unable to process color semantics.:\n{0}\n", exp.Message));
      return;
    }

    // Change colors, either foreground or background.
    if (changeBackGround) 
    {
      BackColor = newColor;
      float Bright = BackColor.GetBrightness();
      float Hue = BackColor.GetHue();
      float Sat = BackColor.GetSaturation();
      
      // Make sure that text is readable regardless of the background.
      if (BackColor.GetBrightness() <= .50) 
      {
        ForeColor = Color.White;
      }
      else 
      {
        ForeColor = Color.Black;
      }
    }
    else 
    {
      ForeColor = newColor;
      float Bright = ForeColor.GetBrightness();
      float Hue = ForeColor.GetHue();
      float Sat = ForeColor.GetSaturation();

      // Make sure that text is readable regardless of Foreground.
      if (ForeColor.GetBrightness() <= .50) 
      {
        BackColor = Color.White;
      }
      else 
      {
        BackColor = Color.Black;
      }
    }
    return;
  };

.NET Framework

.NET Framework Client Profile

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference