Made facets deal with java.util.Collection rather than just Object[].

Documented the browsing.* packages.

git-svn-id: http://google-refine.googlecode.com/svn/trunk@330 7d457c2a-affb-35e4-300a-418c747d4874

src/main/java/com/metaweb/gridworks/browsing/ConjunctiveFilteredRows.java

@@ -7,6 +7,10 @@ import com.metaweb.gridworks.browsing.filters.RowFilter;
 import com.metaweb.gridworks.model.Project;
 import com.metaweb.gridworks.model.Row;
 
+/**
+ * Encapsulate logic for visiting rows that match all give row filters. Also visit
+ * context rows and dependent rows if configured so.
+ */
 public class ConjunctiveFilteredRows implements FilteredRows {
     final protected List<RowFilter> _rowFilters = new LinkedList<RowFilter>();
     final protected boolean         _includeContextual;
@@ -22,61 +26,67 @@ public class ConjunctiveFilteredRows implements FilteredRows {
     }
     
     public void accept(Project project, RowVisitor visitor) {
-        int lastVisitedRow = -1;
+        int lastVisitedRowRowIndex = -1;
-    	int lastRecordRowAccepted = -1;
+    	int lastRecordRowAcceptedRowIndex = -1;
     	
     	int c = project.rows.size();
-        for (int i = 0; i < c; i++) {
+        for (int rowIndex = 0; rowIndex < c; rowIndex++) {
-            Row row = project.rows.get(i);
+            Row row = project.rows.get(rowIndex);
             
-            if (checkRow(project, i, row)) {
+            if (matchRow(project, rowIndex, row)) {
             	if (row.recordIndex >= 0) {
-            		// this is a record row itself
+            		lastRecordRowAcceptedRowIndex = rowIndex; // this is a record row itself
-            		
-            		lastRecordRowAccepted = i;
             	}
             	
-            	visitRow(project, visitor, i, row, lastVisitedRow);
+            	visitRow(project, visitor, rowIndex, row, lastVisitedRowRowIndex);
             	
-                lastVisitedRow = i;
+                lastVisitedRowRowIndex = rowIndex;
             } else if (
+                // this row doesn't match by itself but ...
+                // we want to include dependent rows
+                
             	_includeDependent &&
+            	// and this row is a dependent row since it's not a record row
             	row.recordIndex < 0 &&
             	row.contextRows != null &&
-            	row.contextRows.size() > 0) {
+            	row.contextRows.size() > 0
+            ) {
             	
-            	if (row.contextRows.get(0) == lastRecordRowAccepted) {
+            	if (row.contextRows.get(0) == lastRecordRowAcceptedRowIndex) {
-                    visitor.visit(project, i, row, false, true);
+            	    // this row depends on the last previously matched record row,
-                    lastVisitedRow = i;
+            	    // so we visit it as well as a dependent row
+            	    
+                    visitor.visit(project, rowIndex, row, false, true);
+                    lastVisitedRowRowIndex = rowIndex;
             	}
             }
         }
     }
     
     protected void visitRow(Project project, RowVisitor visitor, int rowIndex, Row row, int lastVisitedRow) {
-    	if (_includeContextual) {
+    	if (_includeContextual &&         // we need to include any context row and
-            if (row.contextRows != null && lastVisitedRow < rowIndex - 1) {
+            row.contextRows != null &&    // this row itself isn't a context row and
-                for (int contextRowIndex : row.contextRows) {
+            lastVisitedRow < rowIndex - 1 // there is definitely some rows before this row
-                    if (contextRowIndex > lastVisitedRow) {
+                                          // that we haven't visited yet
-                        visitor.visit(
+        ) {
-                            project, 
+            for (int contextRowIndex : row.contextRows) {
-                            contextRowIndex, 
+                if (contextRowIndex > lastVisitedRow) {
-                            project.rows.get(contextRowIndex), 
+                    visitor.visit(
-                            true,
+                        project, 
-                            false
+                        contextRowIndex, 
-                        );
+                        project.rows.get(contextRowIndex), 
-                        lastVisitedRow = contextRowIndex;
+                        true, // is visited as a context row
-                    }
+                        false // is not visited as a dependent row
+                    );
+                    lastVisitedRow = contextRowIndex;
                 }
             }
-            
-            visitor.visit(project, rowIndex, row, false, false);
-    	} else {
-            visitor.visit(project, rowIndex, row, false, false);
     	}
+    	
+        visitor.visit(project, rowIndex, row, false, false);
     }
     
-    protected boolean checkRow(Project project, int rowIndex, Row row) {
+    protected boolean matchRow(Project project, int rowIndex, Row row) {
         for (RowFilter rowFilter : _rowFilters) {
             if (!rowFilter.filterRow(project, rowIndex, row)) {
                 return false;

src/main/java/com/metaweb/gridworks/browsing/DecoratedValue.java

@@ -7,9 +7,16 @@ import org.json.JSONWriter;
 
 import com.metaweb.gridworks.Jsonizable;
 
+/**
+ * Store a value and its text label, in case the value is not a string itself.
+ * For instance, if a value is a date, then its label can be one particular
+ * rendering of that date.
+ * 
+ * Facet choices that are presented to the user as text are stored as decorated values.
+ */
 public class DecoratedValue implements Jsonizable {
     final public Object value;
-    final public String    label;
+    final public String label;
     
     public DecoratedValue(Object value, String label) {
         this.value = value;

src/main/java/com/metaweb/gridworks/browsing/Engine.java

@@ -17,6 +17,9 @@ import com.metaweb.gridworks.browsing.facets.TextSearchFacet;
 import com.metaweb.gridworks.browsing.filters.RowFilter;
 import com.metaweb.gridworks.model.Project;
 
+/**
+ * Faceted browsing engine.
+ */
 public class Engine implements Jsonizable {
     protected Project         _project;
     protected List<Facet>     _facets = new LinkedList<Facet>();

src/main/java/com/metaweb/gridworks/browsing/FilteredRows.java

@@ -2,6 +2,18 @@ package com.metaweb.gridworks.browsing;
 
 import com.metaweb.gridworks.model.Project;
 
+/**
+ * Interface for anything that can decide which rows match and which rows don't match
+ * based on some particular criteria.
+ */
 public interface FilteredRows {
+    /**
+     * Go through the rows of the given project, determine which match and which don't,
+     * and call visitor.visit() on those that match, and possibly their context and
+     * dependent rows.
+     * 
+     * @param project
+     * @param visitor
+     */
     public void accept(Project project, RowVisitor visitor);
 }

src/main/java/com/metaweb/gridworks/browsing/RowVisitor.java

@@ -3,12 +3,20 @@ package com.metaweb.gridworks.browsing;
 import com.metaweb.gridworks.model.Project;
 import com.metaweb.gridworks.model.Row;
 
+/**
+ * Interface for visiting rows one by one. The rows visited are only those that match some
+ * particular criteria, such as facets' constraints, or those that are related to the matched
+ * rows. The related rows can be those that the matched rows depend on, or those that depend
+ * on the matched rows.
+ */
 public interface RowVisitor {
     public boolean visit(
 		Project project, 
 		int 	rowIndex,   // zero-based row index 
 		Row 	row, 
-		boolean contextual, // true if this row is included because it's the context row of an included row
+		boolean contextual, // true if this row is included because it's the context row 
-		boolean dependent   // true if this row is included because it depends on an included row
+		                    // of a matched row, that is, a matched row depends on it
+		boolean dependent   // true if this row is included because it depends on a matched row,
+		                    // that is, it depends on a matched row
     );
 }

src/main/java/com/metaweb/gridworks/browsing/facets/ExpressionNominalRowGrouper.java

@@ -1,5 +1,6 @@
 package com.metaweb.gridworks.browsing.facets;
 
+import java.util.Collection;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Properties;
@@ -12,10 +13,20 @@ import com.metaweb.gridworks.model.Cell;
 import com.metaweb.gridworks.model.Project;
 import com.metaweb.gridworks.model.Row;
 
+/**
+ * Visit matched rows and group them into facet choices based on the values computed
+ * from a given expression.
+ */
 public class ExpressionNominalRowGrouper implements RowVisitor {
+    /*
+     * Configuration
+     */
     final protected Evaluable   _evaluable;
     final protected int         _cellIndex;
     
+    /*
+     * Computed results
+     */
     final public Map<Object, NominalFacetChoice> choices = new HashMap<Object, NominalFacetChoice>();
     public int blankCount = 0;
     public int errorCount = 0;
@@ -32,14 +43,22 @@ public class ExpressionNominalRowGrouper implements RowVisitor {
         ExpressionUtils.bind(bindings, row, rowIndex, cell);
         
         Object value = _evaluable.evaluate(bindings);
-        if (value != null && value.getClass().isArray()) {
+        if (value != null) {
-            Object[] a = (Object[]) value;
+            if (value.getClass().isArray()) {
-            for (Object v : a) {
+                Object[] a = (Object[]) value;
-                processValue(v);
+                for (Object v : a) {
-            }
+                    processValue(v);
-        } else {
+                }
-            processValue(value);
+                return false;
+            } else if (value instanceof Collection<?>) {
+                for (Object v : ExpressionUtils.toObjectCollection(value)) {
+                    processValue(v);
+                }
+                return false;
+            } // else, fall through
         }
+        
+        processValue(value);
         return false;
     }
     

src/main/java/com/metaweb/gridworks/browsing/facets/ExpressionNumericRowBinner.java

@@ -1,5 +1,6 @@
 package com.metaweb.gridworks.browsing.facets;
 
+import java.util.Collection;
 import java.util.Properties;
 
 import com.metaweb.gridworks.browsing.RowVisitor;
@@ -9,13 +10,22 @@ import com.metaweb.gridworks.model.Cell;
 import com.metaweb.gridworks.model.Project;
 import com.metaweb.gridworks.model.Row;
 
+/**
+ * Visit matched rows and slot them into bins based on the numbers computed
+ * from a given expression.
+ */
 public class ExpressionNumericRowBinner implements RowVisitor {
+    /*
+     * Configuration
+     */
     final protected Evaluable       _evaluable;
     final protected int             _cellIndex;
-    final protected NumericBinIndex _index;
+    final protected NumericBinIndex _index;     // base bins
     
+    /*
+     * Computed results
+     */
     final public int[] bins;
-    
     public int numericCount;
     public int nonNumericCount;
     public int blankCount;
@@ -35,14 +45,22 @@ public class ExpressionNumericRowBinner implements RowVisitor {
         ExpressionUtils.bind(bindings, row, rowIndex, cell);
         
         Object value = _evaluable.evaluate(bindings);
-        if (value != null && value.getClass().isArray()) {
+        if (value != null) {
-            Object[] a = (Object[]) value;
+            if (value.getClass().isArray()) {
-            for (Object v : a) {
+                Object[] a = (Object[]) value;
-                processValue(v);
+                for (Object v : a) {
-            }
+                    processValue(v);
-        } else {
+                }
-            processValue(value);
+                return false;
+            } else if (value instanceof Collection<?>) {
+                for (Object v : ExpressionUtils.toObjectCollection(value)) {
+                    processValue(v);
+                }
+                return false;
+            } // else, fall through
         }
+        
+        processValue(value);
         return false;
     }
     

src/main/java/com/metaweb/gridworks/browsing/facets/Facet.java

@@ -7,6 +7,9 @@ import com.metaweb.gridworks.browsing.FilteredRows;
 import com.metaweb.gridworks.browsing.filters.RowFilter;
 import com.metaweb.gridworks.model.Project;
 
+/**
+ * Interface of facets.
+ */
 public interface Facet extends Jsonizable {
     public RowFilter getRowFilter();
     

src/main/java/com/metaweb/gridworks/browsing/facets/ListFacet.java

@@ -21,24 +21,31 @@ import com.metaweb.gridworks.model.Project;
 import com.metaweb.gridworks.util.JSONUtilities;
 
 public class ListFacet implements Facet {
-    protected List<NominalFacetChoice> _selection = new LinkedList<NominalFacetChoice>();
+    /*
+     * Configuration
+     */
+    protected String     _name;
+    protected String     _expression;
+    protected String     _columnName;
     
     // If true, then facet won't show the blank and error choices
     protected boolean _omitBlank;
     protected boolean _omitError;
     
+    protected List<NominalFacetChoice> _selection = new LinkedList<NominalFacetChoice>();
     protected boolean _selectBlank;
     protected boolean _selectError;
     
-    protected String     _name;
+    /*
-    protected String     _expression;
+     * Derived configuration
-    protected String     _columnName;
+     */
-    
     protected int        _cellIndex;
     protected Evaluable  _eval;
     protected String     _errorMessage;
     
-    // computed
+    /*
+     * Computed results
+     */
     protected List<NominalFacetChoice> _choices = new LinkedList<NominalFacetChoice>();
     protected int _blankCount;
     protected int _errorCount;
@@ -157,9 +164,20 @@ public class ListFacet implements Facet {
             
             for (NominalFacetChoice choice : _selection) {
                 String valueString = choice.decoratedValue.value.toString();
+                
                 if (grouper.choices.containsKey(valueString)) {
                     grouper.choices.get(valueString).selected = true;
                 } else {
+                    /*
+                     *  A selected choice can have zero count if it is selected together
+                     *  with other choices, and some other facets' constraints eliminate
+                     *  all rows projected to this choice altogether. For example, if you
+                     *  select both "car" and "bicycle" in the "type of vehicle" facet, and
+                     *  then constrain the "wheels" facet to more than 2, then the "bicycle"
+                     *  choice now has zero count even if it's still selected. The grouper 
+                     *  won't be able to detect the "bicycle" choice, so we need to inject
+                     *  that choice into the choice list ourselves.
+                     */
                     choice.count = 0;
                     _choices.add(choice);
                 }

src/main/java/com/metaweb/gridworks/browsing/facets/NominalFacetChoice.java

@@ -8,6 +8,10 @@ import org.json.JSONWriter;
 import com.metaweb.gridworks.Jsonizable;
 import com.metaweb.gridworks.browsing.DecoratedValue;
 
+/**
+ * Store a facet choice that has a decorated value, a count of matched rows,
+ * and a flag of whether it has been selected.
+ */
 public class NominalFacetChoice implements Jsonizable {
     final public DecoratedValue    decoratedValue;
     public int                    count;

src/main/java/com/metaweb/gridworks/browsing/facets/NumericBinIndex.java

@@ -1,6 +1,7 @@
 package com.metaweb.gridworks.browsing.facets;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.List;
 import java.util.Properties;
 
@@ -10,6 +11,16 @@ import com.metaweb.gridworks.model.Cell;
 import com.metaweb.gridworks.model.Project;
 import com.metaweb.gridworks.model.Row;
 
+/**
+ * A utility class for computing the base bins that form the base histograms of 
+ * numeric range facets. It evaluates an expression on all the rows of a project to
+ * get numeric values, determines how many bins to distribute those values in, and 
+ * bins the rows accordingly.
+ * 
+ * This class processes all rows rather than just the filtered rows because it
+ * needs to compute the base bins of a numeric range facet, which remain unchanged 
+ * as the user interacts with the facet.
+ */
 public class NumericBinIndex {
     private double _min;
     private double _max;
@@ -38,6 +49,12 @@ public class NumericBinIndex {
                             processValue(((Number) v).doubleValue(), allValues);
                         }
                     }
+                } else if (value instanceof Collection<?>) {
+                    for (Object v : ExpressionUtils.toObjectCollection(value)) {
+                        if (v instanceof Number) {
+                            processValue(((Number) v).doubleValue(), allValues);
+                        }
+                    }
                 } else if (value instanceof Number) {
                     processValue(((Number) value).doubleValue(), allValues);
                 }

src/main/java/com/metaweb/gridworks/browsing/facets/RangeFacet.java

@@ -17,33 +17,45 @@ import com.metaweb.gridworks.model.Project;
 import com.metaweb.gridworks.util.JSONUtilities;
 
 public class RangeFacet implements Facet {
-    protected String     _name;
+    /*
-    protected String     _expression;
+     * Configuration, from the client side
-    protected String     _columnName;
+     */
+    protected String     _name;       // name of facet
+    protected String     _expression; // expression to compute numeric value(s) per row
+    protected String     _columnName; // column to base expression on, if any
+    protected String     _mode;       // "range", "min", "max"
     
+    protected double    _from; // the numeric selection
+    protected double    _to;
+    
+    protected boolean   _selectNumeric; // whether the numeric selection applies, default true
+    protected boolean   _selectNonNumeric;
+    protected boolean   _selectBlank;
+    protected boolean   _selectError;
+    
+    /*
+     * Derived configuration data
+     */
     protected int        _cellIndex;
     protected Evaluable  _eval;
     protected String     _errorMessage;
+    protected boolean    _selected; // false if we're certain that all rows will match
+                                    // and there isn't any filtering to do
     
-    protected String    _mode;
+    /*
+     * Computed data, to return to the client side
+     */
     protected double    _min;
     protected double    _max;
     protected double    _step;
     protected int[]     _baseBins;
     protected int[]     _bins;
+    
     protected int       _numericCount;
     protected int       _nonNumericCount;
     protected int       _blankCount;
     protected int       _errorCount;
     
-    protected double    _from;
-    protected double    _to;
-    protected boolean   _selected;
-    protected boolean   _selectNumeric;
-    protected boolean   _selectNonNumeric;
-    protected boolean   _selectBlank;
-    protected boolean   _selectError;
-    
     public RangeFacet() {
     }
 

src/main/java/com/metaweb/gridworks/browsing/facets/TextSearchFacet.java

@@ -15,15 +15,21 @@ import com.metaweb.gridworks.gel.ast.VariableExpr;
 import com.metaweb.gridworks.model.Project;
 
 public class TextSearchFacet implements Facet {
+    /*
+     *  Configuration
+     */
     protected String     _name;
     protected String     _columnName;
-    protected int        _cellIndex;
     protected String     _query;
-    protected Pattern    _pattern;
-    
     protected String     _mode;
     protected boolean    _caseSensitive;
     
+    /*
+     *  Derived configuration
+     */
+    protected int        _cellIndex;
+    protected Pattern    _pattern;
+    
     public TextSearchFacet() {
     }
 
@@ -42,6 +48,7 @@ public class TextSearchFacet implements Facet {
     public void initializeFromJSON(Project project, JSONObject o) throws Exception {
         _name = o.getString("name");
         _columnName = o.getString("columnName");
+        
         _cellIndex = project.columnModel.getColumnByName(_columnName).getCellIndex();
         
         if (!o.isNull("query")) {

src/main/java/com/metaweb/gridworks/browsing/filters/ExpressionEqualRowFilter.java

@@ -1,5 +1,6 @@
 package com.metaweb.gridworks.browsing.filters;
 
+import java.util.Collection;
 import java.util.Properties;
 
 import com.metaweb.gridworks.expr.Evaluable;
@@ -8,14 +9,28 @@ import com.metaweb.gridworks.model.Cell;
 import com.metaweb.gridworks.model.Project;
 import com.metaweb.gridworks.model.Row;
 
+/**
+ * Judge if a row matches by evaluating a given expression on the row, based on a particular
+ * column, and checking the result. It's a match if the result is any one of a given list of 
+ * values, or if the result is blank or error and we want blank or error values. 
+ */
 public class ExpressionEqualRowFilter implements RowFilter {
-    final protected Evaluable       _evaluable;
+    final protected Evaluable       _evaluable; // the expression to evaluate
-    final protected int             _cellIndex;
+    final protected int             _cellIndex; // the expression is based on this column;
+                                                // -1 if based on no column in particular,
+                                                // for expression such as "row.starred".
+    
     final protected Object[]        _matches;
     final protected boolean         _selectBlank;
     final protected boolean         _selectError;
     
-    public ExpressionEqualRowFilter(Evaluable evaluable, int cellIndex, Object[] matches, boolean selectBlank, boolean selectError) {
+    public ExpressionEqualRowFilter(
+        Evaluable evaluable, 
+        int cellIndex, 
+        Object[] matches, 
+        boolean selectBlank, 
+        boolean selectError
+    ) {
         _evaluable = evaluable;
         _cellIndex = cellIndex;
         _matches = matches;
@@ -30,17 +45,26 @@ public class ExpressionEqualRowFilter implements RowFilter {
         ExpressionUtils.bind(bindings, row, rowIndex, cell);
         
         Object value = _evaluable.evaluate(bindings);
-        if (value != null && value.getClass().isArray()) {
+        if (value != null) {
-            Object[] a = (Object[]) value;
+            if (value.getClass().isArray()) {
-            for (Object v : a) {
+                Object[] a = (Object[]) value;
-                if (testValue(v)) {
+                for (Object v : a) {
-                    return true;
+                    if (testValue(v)) {
+                        return true;
+                    }
                 }
-            }
+                return false;
-        } else {
+            } else if (value instanceof Collection<?>) {
-            return testValue(value);
+                for (Object v : ExpressionUtils.toObjectCollection(value)) {
+                    if (testValue(v)) {
+                        return true;
+                    }
+                }
+                return false;
+            } // else, fall through
         }
-        return false;
+        
+        return testValue(value);
     }
     
     protected boolean testValue(Object v) {

src/main/java/com/metaweb/gridworks/browsing/filters/ExpressionNumberComparisonRowFilter.java

@@ -1,5 +1,6 @@
 package com.metaweb.gridworks.browsing.filters;
 
+import java.util.Collection;
 import java.util.Properties;
 
 import com.metaweb.gridworks.expr.Evaluable;
@@ -8,6 +9,12 @@ import com.metaweb.gridworks.model.Cell;
 import com.metaweb.gridworks.model.Project;
 import com.metaweb.gridworks.model.Row;
 
+/**
+ * Judge if a row matches by evaluating a given expression on the row, based on a particular
+ * column, and checking the result. It's a match if the result satisfies some numeric comparisons, 
+ * or if the result is non-numeric or blank or error and we want non-numeric or blank or error 
+ * values. 
+ */
 abstract public class ExpressionNumberComparisonRowFilter implements RowFilter {
     final protected Evaluable  _evaluable;
     final protected int        _cellIndex;
@@ -33,25 +40,32 @@ abstract public class ExpressionNumberComparisonRowFilter implements RowFilter {
     }
 
     public boolean filterRow(Project project, int rowIndex, Row row) {
-        Cell cell = row.getCell(_cellIndex);
+        Cell cell = _cellIndex < 0 ? null : row.getCell(_cellIndex);
 
         Properties bindings = ExpressionUtils.createBindings(project);
         ExpressionUtils.bind(bindings, row, rowIndex, cell);
         
         Object value = _evaluable.evaluate(bindings);
-        if (value != null && value.getClass().isArray()) {
+        if (value != null) {
-            Object[] a = (Object[]) value;
+            if (value.getClass().isArray()) {
-            for (Object v : a) {
+                Object[] a = (Object[]) value;
-                if (checkValue(v)) {
+                for (Object v : a) {
-                    return true;
+                    if (checkValue(v)) {
+                        return true;
+                    }
                 }
-            }
+                return false;
-        } else {
+            } else if (value instanceof Collection<?>) {
-            if (checkValue(value)) {
+                for (Object v : ExpressionUtils.toObjectCollection(value)) {
-                return true;
+                    if (checkValue(v)) {
-            }
+                        return true;
+                    }
+                }
+                return false;
+            } // else, fall through
         }
-        return false;
+        
+        return checkValue(value);
     }
         
     protected boolean checkValue(Object v) {

src/main/java/com/metaweb/gridworks/browsing/filters/ExpressionStringComparisonRowFilter.java

@@ -8,9 +8,13 @@ import com.metaweb.gridworks.model.Cell;
 import com.metaweb.gridworks.model.Project;
 import com.metaweb.gridworks.model.Row;
 
+/**
+ * Judge if a row matches by evaluating a given expression on the row, based on a particular
+ * column, and checking the result. It's a match if the result satisfies some string comparisons. 
+ */
 abstract public class ExpressionStringComparisonRowFilter implements RowFilter {
-    final protected Evaluable        _evaluable;
+    final protected Evaluable _evaluable;
-    final protected int             _cellIndex;
+    final protected int       _cellIndex;
     
     public ExpressionStringComparisonRowFilter(Evaluable evaluable, int cellIndex) {
         _evaluable = evaluable;
@@ -18,7 +22,8 @@ abstract public class ExpressionStringComparisonRowFilter implements RowFilter {
     }
 
     public boolean filterRow(Project project, int rowIndex, Row row) {
-        Cell cell = row.getCell(_cellIndex);
+        Cell cell = _cellIndex < 0 ? null : row.getCell(_cellIndex);
+        
         Properties bindings = ExpressionUtils.createBindings(project);
         ExpressionUtils.bind(bindings, row, rowIndex, cell);
         

src/main/java/com/metaweb/gridworks/browsing/filters/RowFilter.java

@@ -3,6 +3,10 @@ package com.metaweb.gridworks.browsing.filters;
 import com.metaweb.gridworks.model.Project;
 import com.metaweb.gridworks.model.Row;
 
+/**
+ * Interface for judging if a particular row matches or doesn't match some
+ * particular criterion, such as a facet constraint.
+ */
 public interface RowFilter {
     public boolean filterRow(Project project, int rowIndex, Row row);
 }