Starts to implement algebra for selection

src/sparql/algebra.rs

@@ -1,5 +1,6 @@
 use model::*;
 use sparql::model::*;
+use std::collections::BTreeSet;
 use std::fmt;
 use std::ops::Add;
 use utils::Escaper;
@@ -398,12 +399,24 @@ impl fmt::Display for Expression {
     }
 }
 
+impl From<NamedNode> for Expression {
+    fn from(p: NamedNode) -> Self {
+        Expression::ConstantExpression(p.into())
+    }
+}
+
 impl From<Literal> for Expression {
     fn from(p: Literal) -> Self {
         Expression::ConstantExpression(p.into())
     }
 }
 
+impl From<Variable> for Expression {
+    fn from(v: Variable) -> Self {
+        Expression::ConstantExpression(v.into())
+    }
+}
+
 struct SparqlExpression<'a>(&'a Expression);
 
 impl<'a> fmt::Display for SparqlExpression<'a> {
@@ -794,6 +807,51 @@ impl From<ListPattern> for MultiSetPattern {
     }
 }
 
+impl MultiSetPattern {
+    pub fn visible_variables<'a>(&'a self) -> BTreeSet<&'a Variable> {
+        let mut vars = BTreeSet::default();
+        self.add_visible_variables(&mut vars);
+        vars
+    }
+
+    fn add_visible_variables<'a>(&'a self, vars: &mut BTreeSet<&'a Variable>) {
+        match self {
+            MultiSetPattern::BGP(p) => {
+                for pattern in p {
+                    if let TermOrVariable::Variable(ref s) = pattern.subject {
+                        vars.insert(s);
+                    }
+                    //TODO: pred
+                    if let TermOrVariable::Variable(ref o) = pattern.object {
+                        vars.insert(o);
+                    }
+                }
+            }
+            MultiSetPattern::Join(a, b) => {
+                a.add_visible_variables(vars);
+                b.add_visible_variables(vars);
+            }
+            MultiSetPattern::LeftJoin(a, b, _) => {
+                a.add_visible_variables(vars);
+                b.add_visible_variables(vars);
+            }
+            MultiSetPattern::Filter(_, p) => p.add_visible_variables(vars),
+            MultiSetPattern::Union(a, b) => {
+                a.add_visible_variables(vars);
+                b.add_visible_variables(vars);
+            }
+            MultiSetPattern::Graph(_, p) => p.add_visible_variables(vars),
+            MultiSetPattern::Extend(p, v, _) => {
+                p.add_visible_variables(vars);
+                vars.insert(&v);
+            }
+            MultiSetPattern::Minus(a, _) => a.add_visible_variables(vars),
+            MultiSetPattern::ToMultiSet(l) => l.add_visible_variables(vars),
+            MultiSetPattern::Service(_, p, _) => p.add_visible_variables(vars),
+        }
+    }
+}
+
 struct SparqlMultiSetPattern<'a>(&'a MultiSetPattern);
 
 impl<'a> fmt::Display for SparqlMultiSetPattern<'a> {
@@ -854,7 +912,14 @@ impl<'a> fmt::Display for SparqlMultiSetPattern<'a> {
                 SparqlMultiSetPattern(&*a),
                 SparqlMultiSetPattern(&*b)
             ),
-            MultiSetPattern::ToMultiSet(l) => write!(f, "{}", SparqlListPattern(&l)),
+            MultiSetPattern::ToMultiSet(l) => write!(
+                f,
+                "{{ {} }}",
+                SparqlListPattern {
+                    algebra: &l,
+                    dataset: &EMPTY_DATASET
+                }
+            ),
             MultiSetPattern::Service(n, p, s) => if *s {
                 write!(
                     f,
@@ -873,14 +938,56 @@ impl<'a> fmt::Display for SparqlMultiSetPattern<'a> {
 pub enum ListPattern {
     Data(Vec<Binding>),
     ToList(MultiSetPattern),
-    Group(),
-    Aggregation(),
-    AggregateJoin(),
-    OrderBy(Box<MultiSetPattern>),
-    Project(Box<MultiSetPattern>),
-    Distinct(Box<MultiSetPattern>),
-    Reduced(Box<MultiSetPattern>),
-    Slice(Box<MultiSetPattern>, usize, usize),
+    OrderBy(Box<ListPattern>, Vec<OrderComparator>),
+    Project(Box<ListPattern>, Vec<Variable>),
+    Distinct(Box<ListPattern>),
+    Reduced(Box<ListPattern>),
+    Slice(Box<ListPattern>, usize, Option<usize>),
+}
+
+impl fmt::Display for ListPattern {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            ListPattern::Data(bs) => write!(
+                f,
+                "{{ {} }}",
+                bs.iter()
+                    .map(|c| c.to_string())
+                    .collect::<Vec<String>>()
+                    .join(" ")
+            ),
+            ListPattern::ToList(l) => write!(f, "{}", l),
+            ListPattern::OrderBy(l, o) => write!(
+                f,
+                "OrderBy({}, ({}))",
+                l,
+                o.iter()
+                    .map(|c| c.to_string())
+                    .collect::<Vec<String>>()
+                    .join(", ")
+            ),
+            ListPattern::Project(l, pv) => write!(
+                f,
+                "Project({}, ({}))",
+                l,
+                pv.iter()
+                    .map(|v| v.to_string())
+                    .collect::<Vec<String>>()
+                    .join(", ")
+            ),
+            ListPattern::Distinct(l) => write!(f, "Distinct({})", l),
+            ListPattern::Reduced(l) => write!(f, "Reduce({})", l),
+            ListPattern::Slice(l, start, length) => write!(
+                f,
+                "Slice({}, {}, {})",
+                l,
+                start,
+                length
+                    .map(|l| l.to_string())
+                    .unwrap_or_else(|| '?'.to_string())
+            ),
+        }
+    }
 }
 
 impl Default for ListPattern {
@@ -898,22 +1005,190 @@ impl From<MultiSetPattern> for ListPattern {
     }
 }
 
-impl fmt::Display for ListPattern {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+impl ListPattern {
+    pub fn visible_variables<'a>(&'a self) -> BTreeSet<&'a Variable> {
+        let mut vars = BTreeSet::default();
+        self.add_visible_variables(&mut vars);
+        vars
+    }
+
+    fn add_visible_variables<'a>(&'a self, vars: &mut BTreeSet<&'a Variable>) {
         match self {
-            ListPattern::ToList(l) => write!(f, "{}", l),
-            _ => Ok(()), //TODO
+            ListPattern::Data(b) => {
+                for binding in b {
+                    for (var, _) in binding {
+                        vars.insert(var);
+                    }
+                }
+            }
+            ListPattern::ToList(p) => p.add_visible_variables(vars),
+            ListPattern::OrderBy(l, _) => l.add_visible_variables(vars),
+            ListPattern::Project(_, pv) => vars.extend(pv.iter()),
+            ListPattern::Distinct(l) => l.add_visible_variables(vars),
+            ListPattern::Reduced(l) => l.add_visible_variables(vars),
+            ListPattern::Slice(l, _, _) => l.add_visible_variables(vars),
         }
     }
 }
 
-struct SparqlListPattern<'a>(&'a ListPattern);
+struct SparqlListPattern<'a> {
+    algebra: &'a ListPattern,
+    dataset: &'a Dataset,
+}
 
 impl<'a> fmt::Display for SparqlListPattern<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self.algebra {
+            ListPattern::Data(bs) => if bs.is_empty() {
+                Ok(())
+            } else {
+                let vars: Vec<&Variable> = bs[0].iter().map(|(v, _)| v).collect();
+                write!(f, "VALUES ( ")?;
+                for var in &vars {
+                    write!(f, "{} ", var)?;
+                }
+                write!(f, ") {{ ")?;
+                for b in bs {
+                    write!(f, "( ")?;
+                    for var in &vars {
+                        b.get(var)
+                            .map(|v| write!(f, "{} ", v))
+                            .unwrap_or_else(|| write!(f, "UNDEF "))?;
+                    }
+                    write!(f, ") ")?;
+                }
+                write!(f, " }}")
+            },
+            ListPattern::ToList(l) => write!(f, "{}", SparqlMultiSetPattern(&*l)),
+            ListPattern::OrderBy(l, o) => write!(
+                f,
+                "{} ORDER BY {}",
+                SparqlListPattern {
+                    algebra: &*l,
+                    dataset: self.dataset
+                },
+                o.iter()
+                    .map(|c| SparqlOrderComparator(c).to_string())
+                    .collect::<Vec<String>>()
+                    .join(" ")
+            ),
+            ListPattern::Project(l, pv) => write!(
+                f,
+                "SELECT {} {} WHERE {{ {} }}",
+                build_sparql_select_arguments(pv),
+                self.dataset,
+                SparqlListPattern {
+                    algebra: &*l,
+                    dataset: &EMPTY_DATASET
+                }
+            ),
+            ListPattern::Distinct(l) => match l.as_ref() {
+                ListPattern::Project(l, pv) => write!(
+                    f,
+                    "SELECT DISTINCT {} {} WHERE {{ {} }}",
+                    build_sparql_select_arguments(pv),
+                    self.dataset,
+                    SparqlListPattern {
+                        algebra: &*l,
+                        dataset: &EMPTY_DATASET
+                    }
+                ),
+                l => write!(
+                    f,
+                    "DISTINCT {}",
+                    SparqlListPattern {
+                        algebra: &l,
+                        dataset: self.dataset
+                    }
+                ),
+            },
+            ListPattern::Reduced(l) => match l.as_ref() {
+                ListPattern::Project(l, pv) => write!(
+                    f,
+                    "SELECT REDUCED {} {} WHERE {{ {} }}",
+                    build_sparql_select_arguments(pv),
+                    self.dataset,
+                    SparqlListPattern {
+                        algebra: &*l,
+                        dataset: &EMPTY_DATASET
+                    }
+                ),
+                l => write!(
+                    f,
+                    "REDUCED {}",
+                    SparqlListPattern {
+                        algebra: &l,
+                        dataset: self.dataset
+                    }
+                ),
+            },
+            ListPattern::Slice(l, start, length) => length
+                .map(|length| {
+                    write!(
+                        f,
+                        "{} LIMIT {} OFFSET {}",
+                        SparqlListPattern {
+                            algebra: &*l,
+                            dataset: self.dataset
+                        },
+                        start,
+                        length
+                    )
+                })
+                .unwrap_or_else(|| {
+                    write!(
+                        f,
+                        "{} LIMIT {}",
+                        SparqlListPattern {
+                            algebra: &*l,
+                            dataset: self.dataset
+                        },
+                        start
+                    )
+                }),
+        }
+    }
+}
+
+fn build_sparql_select_arguments(args: &Vec<Variable>) -> String {
+    if args.is_empty() {
+        "*".to_owned()
+    } else {
+        args.iter()
+            .map(|v| v.to_string())
+            .collect::<Vec<String>>()
+            .join(" ")
+    }
+}
+
+#[derive(Eq, PartialEq, Ord, PartialOrd, Debug, Clone, Hash)]
+pub enum OrderComparator {
+    Asc(Expression),
+    Desc(Expression),
+}
+
+impl fmt::Display for OrderComparator {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            OrderComparator::Asc(e) => write!(f, "ASC({})", e),
+            OrderComparator::Desc(e) => write!(f, "DESC({})", e),
+        }
+    }
+}
+
+impl From<Expression> for OrderComparator {
+    fn from(e: Expression) -> Self {
+        OrderComparator::Asc(e)
+    }
+}
+
+struct SparqlOrderComparator<'a>(&'a OrderComparator);
+
+impl<'a> fmt::Display for SparqlOrderComparator<'a> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match self.0 {
-            ListPattern::ToList(l) => write!(f, "{}", SparqlMultiSetPattern(&l)),
-            _ => Ok(()), //TODO
+            OrderComparator::Asc(e) => write!(f, "ASC({})", SparqlExpression(e)),
+            OrderComparator::Desc(e) => write!(f, "DESC({})", SparqlExpression(e)),
         }
     }
 }
@@ -962,103 +1237,46 @@ impl fmt::Display for Dataset {
     }
 }
 
-#[derive(Eq, PartialEq, Ord, PartialOrd, Debug, Clone, Hash)]
-pub enum SelectionOption {
-    Distinct,
-    Reduced,
-    Default,
-}
-
-impl fmt::Display for SelectionOption {
-    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
-        match self {
-            SelectionOption::Distinct => write!(f, "DISTINCT"),
-            SelectionOption::Reduced => write!(f, "REDUCED"),
-            SelectionOption::Default => Ok(()),
-        }
-    }
-}
-
-#[derive(Eq, PartialEq, Ord, PartialOrd, Debug, Clone, Hash)]
-pub enum SelectionMember {
-    Variable(Variable),
-    Expression(Expression, Variable),
-}
-
-impl fmt::Display for SelectionMember {
-    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
-        match self {
-            SelectionMember::Variable(v) => write!(f, "{}", v),
-            SelectionMember::Expression(e, v) => write!(f, "({} AS {})", e, v),
-        }
-    }
-}
-
-#[derive(Eq, PartialEq, Ord, PartialOrd, Debug, Clone, Hash)]
-pub struct Selection {
-    pub option: SelectionOption,
-    pub variables: Option<Vec<SelectionMember>>,
-}
-
-impl fmt::Display for Selection {
-    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
-        self.variables
-            .as_ref()
-            .map(|vars| {
-                write!(
-                    f,
-                    "{} {}",
-                    self.option,
-                    vars.iter()
-                        .map(|v| v.to_string())
-                        .collect::<Vec<String>>()
-                        .join(" ")
-                )
-            })
-            .unwrap_or_else(|| write!(f, "{} *", self.option))
-    }
+lazy_static! {
+    static ref EMPTY_DATASET: Dataset = Dataset::default();
 }
 
 #[derive(Eq, PartialEq, Ord, PartialOrd, Debug, Clone, Hash)]
 pub enum Query {
     SelectQuery {
-        selection: Selection,
         dataset: Dataset,
-        filter: ListPattern,
+        algebra: ListPattern,
     },
     ConstructQuery {
         construct: Vec<TriplePattern>,
         dataset: Dataset,
-        filter: ListPattern,
+        algebra: ListPattern,
     },
     DescribeQuery {
         dataset: Dataset,
-        filter: ListPattern,
+        algebra: ListPattern,
     },
     AskQuery {
         dataset: Dataset,
-        filter: ListPattern,
+        algebra: ListPattern,
     },
 }
 
 impl fmt::Display for Query {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match self {
-            Query::SelectQuery {
-                selection,
-                dataset,
-                filter,
-            } => write!(
+            Query::SelectQuery { dataset, algebra } => write!(
                 f,
-                "SELECT {} {} WHERE {{ {} }}",
-                selection,
-                dataset,
-                SparqlListPattern(&filter)
+                "{}",
+                SparqlListPattern {
+                    algebra: &algebra,
+                    dataset: &dataset
+                }
             ),
             Query::ConstructQuery {
                 construct,
                 dataset,
-                filter,
+                algebra,
             } => write!(
                 f,
                 "CONSTRUCT {{ {} }} {} WHERE {{ {} }}",
@@ -1068,19 +1286,28 @@ impl fmt::Display for Query {
                     .collect::<Vec<String>>()
                     .join(" . "),
                 dataset,
-                SparqlListPattern(&filter)
+                SparqlListPattern {
+                    algebra: &algebra,
+                    dataset: &EMPTY_DATASET
+                }
             ),
-            Query::DescribeQuery { dataset, filter } => write!(
+            Query::DescribeQuery { dataset, algebra } => write!(
                 f,
                 "DESCRIBE {} WHERE {{ {} }}",
                 dataset,
-                SparqlListPattern(&filter)
+                SparqlListPattern {
+                    algebra: &algebra,
+                    dataset: &EMPTY_DATASET
+                }
             ),
-            Query::AskQuery { dataset, filter } => write!(
+            Query::AskQuery { dataset, algebra } => write!(
                 f,
                 "ASK {} WHERE {{ {} }}",
                 dataset,
-                SparqlListPattern(&filter)
+                SparqlListPattern {
+                    algebra: &algebra,
+                    dataset: &EMPTY_DATASET
+                }
             ),
         }
     }

src/sparql/model.rs

@@ -1,4 +1,5 @@
 use model::*;
+use std::collections::btree_map;
 use std::collections::BTreeMap;
 use std::fmt;
 use uuid::Uuid;
@@ -150,12 +151,20 @@ impl Binding {
         self.0.insert(var, value);
     }
 
-    pub fn get<'a>(&'a self, key: &'a TermOrVariable) -> Option<&'a Term> {
+    pub fn get<'a>(&'a self, key: &'a Variable) -> Option<&'a Term> {
+        self.0.get(key)
+    }
+
+    pub fn get_or_constant<'a>(&'a self, key: &'a TermOrVariable) -> Option<&'a Term> {
         match key {
             TermOrVariable::Term(t) => Some(t),
-            TermOrVariable::Variable(v) => self.0.get(v),
+            TermOrVariable::Variable(v) => self.get(v),
         }
     }
+
+    pub fn iter<'a>(&'a self) -> btree_map::Iter<Variable, Term> {
+        self.0.iter()
+    }
 }
 
 impl Default for Binding {
@@ -163,3 +172,31 @@ impl Default for Binding {
         Binding(BTreeMap::default())
     }
 }
+
+impl IntoIterator for Binding {
+    type Item = (Variable, Term);
+    type IntoIter = btree_map::IntoIter<Variable, Term>;
+
+    fn into_iter(self) -> btree_map::IntoIter<Variable, Term> {
+        self.0.into_iter()
+    }
+}
+
+impl<'a> IntoIterator for &'a Binding {
+    type Item = (&'a Variable, &'a Term);
+    type IntoIter = btree_map::Iter<'a, Variable, Term>;
+
+    fn into_iter(self) -> btree_map::Iter<'a, Variable, Term> {
+        self.0.iter()
+    }
+}
+
+impl fmt::Display for Binding {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{{")?;
+        for (var, val) in self {
+            write!(f, " {} → {} ", var, val)?;
+        }
+        write!(f, "}}")
+    }
+}

src/sparql/parser.rs

@@ -132,6 +132,68 @@ mod grammar {
         }).ok_or("The iterator should not be empty")
     }
 
+    enum SelectionOption {
+        Distinct,
+        Reduced,
+        Default,
+    }
+
+    enum SelectionMember {
+        Variable(Variable),
+        Expression(Expression, Variable),
+    }
+
+    struct Selection {
+        pub option: SelectionOption,
+        pub variables: Option<Vec<SelectionMember>>,
+    }
+
+    fn build_select(
+        select: Selection,
+        wher: MultiSetPattern,
+        having: Option<Expression>,
+        order_by: Option<Vec<OrderComparator>>,
+        values: Option<MultiSetPattern>,
+    ) -> ListPattern {
+        let mut p = wher;
+        if let Some(ex) = having {
+            p = MultiSetPattern::Filter(ex, Box::new(p));
+        }
+        if let Some(data) = values {
+            p = MultiSetPattern::Join(Box::new(p), Box::new(data));
+        }
+        let mut pv: Vec<Variable> = Vec::default();
+        match select.variables {
+            Some(sel_items) => {
+                for sel_item in sel_items {
+                    match sel_item {
+                        SelectionMember::Variable(v) => pv.push(v),
+                        SelectionMember::Expression(e, v) => if pv.contains(&v) {
+                            //TODO: fail
+                        } else {
+                            p = MultiSetPattern::Extend(Box::new(p), v.clone(), e);
+                            pv.push(v);
+                        },
+                    }
+                }
+            }
+            None => {
+                pv.extend(p.visible_variables().into_iter().map(|v| v.clone())) //TODO: is it really useful to do a projection?
+            }
+        }
+        let mut m = ListPattern::from(p);
+        if let Some(order) = order_by {
+            m = ListPattern::OrderBy(Box::new(m), order);
+        }
+        m = ListPattern::Project(Box::new(m), pv);
+        match select.option {
+            SelectionOption::Distinct => m = ListPattern::Distinct(Box::new(m)),
+            SelectionOption::Reduced => m = ListPattern::Reduced(Box::new(m)),
+            SelectionOption::Default => (),
+        }
+        m
+    }
+
     enum Either<L, R> {
         Left(L),
         Right(R),

src/sparql/sparql_grammar.rustpeg

@@ -13,7 +13,7 @@ use std::iter;
 QueryUnit -> Query = Query
 
 //[2]
-Query -> Query = _ Prologue _ q:(SelectQuery / ConstructQuery / DescribeQuery / AskQuery) _ ValuesClause _ { //TODO: ValuesClause
+Query -> Query = _ Prologue _ q:(SelectQuery / ConstructQuery / DescribeQuery / AskQuery) _ { //TODO: ValuesClause
     q
 }
 
@@ -37,21 +37,16 @@ PrefixDecl -> () = "PREFIX"i _ ns:PNAME_NS _ i:IRIREF {
 }
 
 //[7]
-SelectQuery -> Query = s:SelectClause _ d:DatasetClauses _ f:WhereClause _ SolutionModifier {  //TODO: Modifier
+SelectQuery -> Query = s:SelectClause _ d:DatasetClauses _ w:WhereClause _ GroupClause? _ h:HavingClause? _ o:OrderClause? _ l:LimitOffsetClauses? _ v:ValuesClause {  //TODO: Modifier
     Query::SelectQuery {
-        selection: s,
         dataset: d,
-        filter: f
+        algebra: build_select(s, w, h, o, v)
     }
 }
 
 //[8]
-SubSelect -> MultiSetPattern = s:SelectClause _ f:WhereClause _ SolutionModifier _ ValuesClause { //TODO: Modifiers
-    MultiSetPattern::default()
-    /*TODO MultiSetPattern::SubSelectPattern {
-        selection: s,
-        filter: Box::new(f)
-    }*/
+SubSelect -> MultiSetPattern = s:SelectClause _ w:WhereClause _ GroupClause? _ h:HavingClause? _ o:OrderClause? _ l:LimitOffsetClauses? _ v:ValuesClause { //TODO: Modifiers
+    build_select(s, w, h, o, v).into()
 }
 
 //[9]
@@ -74,32 +69,63 @@ SelectClause_member -> SelectionMember =
 
 //[10]
 ConstructQuery -> Query =
-    "CONSTRUCT"i _ c:ConstructTemplate _ d:DatasetClauses _ f:WhereClause _ SolutionModifier {
-        Query::ConstructQuery { construct: c, dataset: d, filter: f }
+    "CONSTRUCT"i _ c:ConstructTemplate _ d:DatasetClauses _ w:WhereClause _ GroupClause? _ h:HavingClause? _ o:OrderClause? _ LimitOffsetClauses? _ v:ValuesClause {
+        Query::ConstructQuery {
+            construct: c,
+            dataset: d,
+            algebra: build_select(Selection {
+                option: SelectionOption::Reduced,
+                variables: None
+            }, w, h, o, v)
+        }
     } /
-    "CONSTRUCT"i _ d:DatasetClauses _ "WHERE"i _ '{' _ c:ConstructQuery_optional_triple_template _ '}' _ SolutionModifier {
+    "CONSTRUCT"i _ d:DatasetClauses _ "WHERE"i _ '{' _ c:ConstructQuery_optional_triple_template _ '}' _ GroupClause? _ h:HavingClause? _ o:OrderClause? _ LimitOffsetClauses? _ v:ValuesClause {
         Query::ConstructQuery {
             construct: c.clone(),
             dataset: d,
-            filter: MultiSetPattern::BGP(c.into_iter().map(|p| PropertyPathPattern::from(p)).collect()).into()
+            algebra: build_select(Selection {
+                option: SelectionOption::Reduced,
+                variables: None
+            }, MultiSetPattern::BGP(c.into_iter().map(|p| PropertyPathPattern::from(p)).collect()).into(),
+            h, o, v)
         }
     }
 
 ConstructQuery_optional_triple_template -> Vec<TriplePattern> = TriplesTemplate / { Vec::default() }
 
 //[11]
-DescribeQuery -> Query = "DESCRIBE"i _ ('*' / (VarOrIri _)+) _ d:DatasetClauses f:WhereClause? _ SolutionModifier {
-    Query::DescribeQuery {
-        dataset: d,
-        filter: f.unwrap_or_else(ListPattern::default)
+DescribeQuery -> Query =
+    "DESCRIBE"i _ '*' _ d:DatasetClauses w:WhereClause? _ GroupClause? _ h:HavingClause? _ o:OrderClause? _ LimitOffsetClauses? _ v:ValuesClause {
+        Query::DescribeQuery {
+            dataset: d,
+            algebra: build_select(Selection {
+                option: SelectionOption::Reduced,
+                variables: None
+            }, w.unwrap_or_else(MultiSetPattern::default), h, o, v)
+        }
+    } /
+    "DESCRIBE"i _ p:DescribeQuery_item+ _ d:DatasetClauses w:WhereClause? _ GroupClause? _ h:HavingClause? _ o:OrderClause? _ LimitOffsetClauses? _ v:ValuesClause {
+        Query::DescribeQuery {
+            dataset: d,
+            algebra: build_select(Selection {
+                option: SelectionOption::Reduced,
+                variables: Some(p.into_iter().map(|var_or_iri| match var_or_iri {
+                    NamedNodeOrVariable::NamedNode(n) => SelectionMember::Expression(n.into(), Variable::default()),
+                    NamedNodeOrVariable::Variable(v) => SelectionMember::Variable(v)
+                }).collect())
+            }, w.unwrap_or_else(MultiSetPattern::default), h, o, v)
+        }
     }
-}
+DescribeQuery_item -> NamedNodeOrVariable = i:VarOrIri _ { i }
 
 //[12]
-AskQuery -> Query = "ASK"i _ d:DatasetClauses f:WhereClause _ SolutionModifier {
+AskQuery -> Query = "ASK"i _ d:DatasetClauses w:WhereClause _ GroupClause? _ h:HavingClause? _ o:OrderClause? _ LimitOffsetClauses? _ v:ValuesClause {
     Query::AskQuery {
         dataset: d,
-        filter: f
+        algebra: build_select(Selection {
+            option: SelectionOption::Reduced,
+            variables: None
+        }, w, h, o, v)
     }
 }
 
@@ -123,13 +149,10 @@ NamedGraphClause -> Dataset = "NAMED"i _ s:SourceSelector {
 SourceSelector -> NamedNode = iri
 
 //[17]
-WhereClause -> ListPattern = "WHERE"i? _ p:GroupGraphPattern {
-    p.into()
+WhereClause -> MultiSetPattern = "WHERE"i? _ p:GroupGraphPattern {
+    p
 }
 
-//[18]
-SolutionModifier -> () = GroupClause? _ HavingClause? _ OrderClause? _ LimitOffsetClauses?
-
 //[19]
 GroupClause -> () = "GROUP"i _ "BY"i _ (GroupCondition _)+
 
@@ -145,10 +168,15 @@ HavingClause -> Expression = "HAVING"i _ e:HavingCondition+ {?
 HavingCondition -> Expression = Constraint
 
 //[23]
-OrderClause -> () = "ORDER"i "BY"i _ OrderCondition+
+OrderClause -> Vec<OrderComparator> = "ORDER"i "BY"i _ c:OrderClause_item+ { c }
+OrderClause_item -> OrderComparator = c:OrderCondition _ { c }
 
 //[24]
-OrderCondition -> () = (( "ASC"i / "DESC"i) _ BrackettedExpression) / (Constraint / Var)
+OrderCondition -> OrderComparator =
+    "ASC"i _ e: BrackettedExpression { OrderComparator::Asc(e) } /
+    "DESC"i _ e: BrackettedExpression { OrderComparator::Desc(e) } /
+    e: Constraint { e.into() } /
+    v: Var { Expression::from(v).into() }
 
 //[25]
 LimitOffsetClauses -> () = LimitClause _ OffsetClause? / OffsetClause _ LimitClause?