diff --git a/src/parser.js b/src/parser.js
index c83eb63..6fb4394 100644
--- a/src/parser.js
+++ b/src/parser.js
@@ -1,7 +1,6 @@
 import { Result } from './result.js'
 import { Iterator, Stream } from './stream.js'
-import { curry, head, join, of } from './fn.js'
-import { pipe } from 'bitecs'
+import { pipe, curry, head, join, of } from './fn.js'
 
 class ParseError extends Error {
   constructor(message, state, source) {
@@ -159,6 +158,8 @@ export const map = curry((fn, parser, state) => {
   return result
 })
 
+export const map1 = curry((fn, parser, state) => map(([x]) => fn(x), parser, state))
+export const always = curry((value, parser, state) => map(() => value, parser, state))
 
 export const anyChar = state => {
   const ch = next(state)
diff --git a/src/query-parser/common.js b/src/query-parser/common.js
index 829e653..f05e216 100644
--- a/src/query-parser/common.js
+++ b/src/query-parser/common.js
@@ -2,7 +2,7 @@ import { join } from '../fn.js'
 import { alpha, alphanumeric, any, char, digit, list, many, map, maybe, noCaseString, separated, seq, skip, string, until } from '../parser.js'
 import { Alias, Identifier, Literal, ObjectPath, Property } from './types.js'
 
-export const Symbol = Object.freeze({
+export const Symbols = Object.freeze({
   Bracket: Object.freeze({
     Angle: Object.freeze({
       Left: char('<'),
@@ -23,6 +23,7 @@ export const Symbol = Object.freeze({
   }),
   Colon: char(':'),
   Comma: char(','),
+  Equal: char('='),
   Hyphen: char('-'),
   Newline: char('\n'),
   Tab: char('\t'),
@@ -34,20 +35,20 @@ export const Symbol = Object.freeze({
 
 export const word = value => seq(skip(ws), value, skip(ws))
 export const collect = parser => map(join(''), parser)
-export const quoted = collect(seq(skip(Symbol.Quote), until(Symbol.Quote), skip(Symbol.Quote)))
+export const quoted = collect(seq(skip(Symbols.Quote), until(Symbols.Quote), skip(Symbols.Quote)))
 export const number = seq(digit, many(digit))
-export const signed = seq(maybe(any(Symbol.Plus, Symbol.Hyphen)), number)
-export const ws = skip(many(any(Symbol.Newline, Symbol.Space, Symbol.Tab)))
+export const signed = seq(maybe(any(Symbols.Plus, Symbols.Hyphen)), number)
+export const ws = skip(many(any(Symbols.Newline, Symbols.Space, Symbols.Tab)))
 export const identifier = map(([x]) => new Identifier(x), collect(seq(alpha, many(alphanumeric))))
 
-const float = map(([n]) => parseFloat(n, 10), collect(seq(signed, Symbol.Period, number)))
+const float = map(([n]) => parseFloat(n, 10), collect(seq(signed, Symbols.Period, number)))
 const integer = map(([n]) => parseInt(n, 10), collect(signed))
 const str = quoted
 
 const toBoolean = v => v === 'false' ? false : true
 const boolean = map(([v]) => toBoolean(v), any(string('true'), string('false')))
 
-const property = map(([x]) => new Property(x), seq(skip(Symbol.Period), identifier))
+const property = map(([x]) => new Property(x), seq(skip(Symbols.Period), identifier))
 const accessor = map(x => new ObjectPath(...x), seq(identifier, property, many(property)))
 
 export const literal = map(([x]) => new Literal(x), any(float, integer, str, boolean))
diff --git a/src/query-parser/types.js b/src/query-parser/types.js
index e82ff1b..3a3b008 100644
--- a/src/query-parser/types.js
+++ b/src/query-parser/types.js
@@ -11,8 +11,8 @@ class Value {
     return this.#value.toString()
   }
 
-  get value() {
-    return this.#value?.value ?? this.#value
+  valueOf() {
+    return this.#value?.valueOf() ?? this.#value
   }
 
   equals(other) {
@@ -86,6 +86,69 @@ export class Literal {
   }
 }
 
+export const None = new Literal(null)
+
+export class Operator {
+  #fn
+
+  constructor(fn, length = fn.length) {
+    this.#fn = fn
+    this.length = length
+  }
+
+  #pop(n, stack) {
+    let result = []
+
+    for(let i = 0; i < n; i++) {
+      result.push(stack.pop())
+    }
+
+    result.reverse()
+    return result
+  }
+
+  apply(stack) {
+    const args = this.#pop(this.length, stack)
+    return this.#fn.apply(undefined, args)
+  }
+}
+
+export class UnaryExpression {
+  constructor(op, value) {
+    this.op = op
+    this.value = value
+  }
+}
+
+export class BinaryExpression {
+  constructor(left, op, right) {
+    this.left = left
+    this.op = op
+    this.right = right
+  }
+}
+
+export const Is = new Operator((x, y) => typeof x === y)
+export const Not = new Operator(x => !x)
+export const And = new Operator((x, y) => x && y)
+export const Or = new Operator((x, y) => x || y)
+export const Xor = new Operator((x, y) => x != y)
+export const GreaterThan = new Operator((x, y) => x > y)
+export const GreaterThanEqual = new Operator((x, y) => x >= y)
+export const LesserThan = new Operator((x, y) => x < y)
+export const LesserThanEqual = new Operator((x, y) => x <= y)
+export const Equal = new Operator((x, y) => x === y)
+
+export class Filter {
+  constructor(...args) {
+    this.values = this.#shufflingYard(args)
+  }
+
+  #shufflingYard(args) {
+    // do the thing
+    return args
+  }
+}
 
 export class Alias extends Identifier {
   constructor(value, alias) {
@@ -101,7 +164,7 @@ export class ObjectPath extends Identifier {
   }
 
   toString() {
-    return `${this.value}.${this.path.join('.')}`
+    return [this.valueOf()].concat(path).join('.')
   }
 
   from(component) {
@@ -231,11 +294,10 @@ class ReturnValue {
   }
 
   withEntity(entity) {
-    return  assocPath(this.#value.toString(), this.#getter(entity), {})
+    return assocPath(this.#value.toString(), this.#getter(entity), {})
   }
 }
 
-
 export class KeyValuePair {
   constructor(key, value) {
     this.key = key
diff --git a/src/query-parser/where.js b/src/query-parser/where.js
new file mode 100644
index 0000000..653b289
--- /dev/null
+++ b/src/query-parser/where.js
@@ -0,0 +1,36 @@
+import { construct } from '../fn.js'
+import { always, any, char, many1, map, map1, noCaseString, seq, skip, string } from '../parser.js'
+import { Symbols, value, word, ws } from './common.js'
+import { And, Equal, Filter, GreaterThan, GreaterThanEqual, LesserThan, LesserThanEqual, Literal, None, Not, Or, Xor } from './types.js'
+
+const { Left, Right } = Symbols.Bracket.Round
+const lparen = map1(construct(Literal), Left)
+const rparen = map1(construct(Literal), Right)
+
+// type and existence
+export const nil = always(None, noCaseString('null'))
+export const is = noCaseString('is')
+
+// binary
+export const gt = always(GreaterThan, char('>'))
+export const gte = always(GreaterThanEqual, string('>='))
+export const lt = always(LesserThan, char('<'))
+export const lte = always(LesserThanEqual, string('<='))
+export const eq = always(Equal, char('='))
+
+export const and = always(And, noCaseString('and'))
+export const or = always(Or, noCaseString('or'))
+export const xor = always(Xor, noCaseString('xor'))
+
+export const compare = any(gte, lte, gt, lt, eq)
+export const logic = any(and, or, xor)
+
+// unary
+export const not = always(Not, noCaseString('not'))
+export const unary = any(not)
+
+export const expr = any(lparen, rparen, compare, logic, unary, value)
+export const params = map(construct(Filter), many1(word(expr)))
+
+const keyword = noCaseString('where')
+export const whereClause = seq(skip(keyword), ws, params)
diff --git a/tests/query-parser/where.test.js b/tests/query-parser/where.test.js
new file mode 100644
index 0000000..c438672
--- /dev/null
+++ b/tests/query-parser/where.test.js
@@ -0,0 +1,90 @@
+import { describe, it } from 'node:test'
+import assert from '../assert.js'
+import { and, eq, expr, gt, gte, lt, lte, not, or, params, whereClause, xor } from '../../src/query-parser/where.js'
+import { And, Equal, Filter, GreaterThan, GreaterThanEqual, LesserThan, LesserThanEqual, Literal, Or } from '../../src/query-parser/types.js'
+
+const l = x => new Literal(x)
+describe('where operators', () => {
+    it('or', () => {
+        assert.parseOk(or, 'OR', ([actual]) => {
+            assert.strictEqual(actual.apply([true, true]), true)
+            assert.strictEqual(actual.apply([false, true]), true)
+            assert.strictEqual(actual.apply([true, false]), true)
+            assert.strictEqual(actual.apply([false, false]), false)
+        })
+    })
+
+    it('and', () => {
+        assert.parseOk(and, 'AND', ([actual]) => {
+            assert.strictEqual(actual.apply([true, true]), true)
+            assert.strictEqual(actual.apply([false, true]), false)
+            assert.strictEqual(actual.apply([true, false]), false)
+            assert.strictEqual(actual.apply([false, false]), false)
+        })
+    })
+
+    it('xor', () => {
+        assert.parseOk(xor, 'XOR', ([actual]) => {
+            assert.strictEqual(actual.apply([true, true]), false)
+            assert.strictEqual(actual.apply([false, true]), true)
+            assert.strictEqual(actual.apply([true, false]), true)
+            assert.strictEqual(actual.apply([false, false]), false)
+        })
+    })
+
+    it('not', () => {
+        assert.parseOk(not, 'NOT', ([actual]) => {
+            assert.strictEqual(actual.apply([true]), false)
+            assert.strictEqual(actual.apply([false]), true)
+        })
+    })
+
+    it('gt', () => {
+        assert.parseOk(gt, '>', ([actual]) => {
+            assert.strictEqual(actual.apply([1, 2]), false)
+            assert.strictEqual(actual.apply([2, 1]), true)
+            assert.strictEqual(actual.apply([1, 1]), false)
+        })
+    })
+
+    it('gte', () => {
+        assert.parseOk(gte, '>=', ([actual]) => {
+            assert.strictEqual(actual.apply([1, 2]), false)
+            assert.strictEqual(actual.apply([2, 1]), true)
+            assert.strictEqual(actual.apply([1, 1]), true)
+        })
+    })
+
+    it('lt', () => {
+        assert.parseOk(lt, '<', ([actual]) => {
+            assert.strictEqual(actual.apply([1, 2]), true)
+            assert.strictEqual(actual.apply([2, 1]), false)
+            assert.strictEqual(actual.apply([1, 1]), false)
+        })
+    })
+
+    it('lte', () => {
+        assert.parseOk(lte, '<=', ([actual]) => {
+            assert.strictEqual(actual.apply([1, 2]), true)
+            assert.strictEqual(actual.apply([2, 1]), false)
+            assert.strictEqual(actual.apply([1, 1]), true)
+        })
+    })
+    
+    it('eq', () => {
+        assert.parseOk(eq, '=', ([actual]) => {
+            assert.strictEqual(actual.apply([1, 2]), false)
+            assert.strictEqual(actual.apply([2, 1]), false)
+            assert.strictEqual(actual.apply([1, 1]), true)
+        })
+    })
+})
+
+describe('WHERE keyword', () => {
+    it('handles complex filters', () => {
+        assert.parseOk(whereClause, 'WHERE 1.1 > 5 AND (1 = 500 OR 2 > 3) OR 5 <= 2', ([actual]) => {
+            const expected = new Filter(l(1.1), GreaterThan, l(5), And, l('('), l(1), Equal, l(500), Or, l(2), GreaterThan, l(3), l(')'), Or, l(5), LesserThanEqual, l(2))
+            assert.deepEqual(actual, expected)
+        })
+    })
+})
\ No newline at end of file