diff --git a/parsers/filters/parse.go b/parsers/filters/parse.go
index 6c394f1..7444201 100644
--- a/parsers/filters/parse.go
+++ b/parsers/filters/parse.go
@@ -5,6 +5,7 @@ package filters
 import (
 	"encoding/json"
 	"errors"
+	"fmt"
 	"regexp"
 	"strings"
 )
@@ -15,7 +16,14 @@ import (
 // in an slice.
 // e.g given -f 'label=label1=1' -f 'label=label2=2' -f 'image.name=ubuntu'
 // the args will be {'label': {'label1=1','label2=2'}, 'image.name', {'ubuntu'}}
-type Args map[string][]string
+type Args struct {
+	fields map[string]map[string]bool
+}
+
+// NewArgs initializes a new Args struct.
+func NewArgs() Args {
+	return Args{fields: map[string]map[string]bool{}}
+}
 
 // ParseFlag parses the argument to the filter flag. Like
 //
@@ -25,9 +33,6 @@ type Args map[string][]string
 // map is created.
 func ParseFlag(arg string, prev Args) (Args, error) {
 	filters := prev
-	if prev == nil {
-		filters = Args{}
-	}
 	if len(arg) == 0 {
 		return filters, nil
 	}
@@ -37,9 +42,11 @@ func ParseFlag(arg string, prev Args) (Args, error) {
 	}
 
 	f := strings.SplitN(arg, "=", 2)
+
 	name := strings.ToLower(strings.TrimSpace(f[0]))
 	value := strings.TrimSpace(f[1])
-	filters[name] = append(filters[name], value)
+
+	filters.Add(name, value)
 
 	return filters, nil
 }
@@ -50,11 +57,11 @@ var ErrBadFormat = errors.New("bad format of filter (expected name=value)")
 // ToParam packs the Args into an string for easy transport from client to server.
 func ToParam(a Args) (string, error) {
 	// this way we don't URL encode {}, just empty space
-	if len(a) == 0 {
+	if a.Len() == 0 {
 		return "", nil
 	}
 
-	buf, err := json.Marshal(a)
+	buf, err := json.Marshal(a.fields)
 	if err != nil {
 		return "", err
 	}
@@ -63,23 +70,71 @@ func ToParam(a Args) (string, error) {
 
 // FromParam unpacks the filter Args.
 func FromParam(p string) (Args, error) {
-	args := Args{}
 	if len(p) == 0 {
-		return args, nil
+		return NewArgs(), nil
 	}
-	if err := json.NewDecoder(strings.NewReader(p)).Decode(&args); err != nil {
-		return nil, err
+
+	r := strings.NewReader(p)
+	d := json.NewDecoder(r)
+
+	m := map[string]map[string]bool{}
+	if err := d.Decode(&m); err != nil {
+		r.Seek(0, 0)
+
+		// Allow parsing old arguments in slice format.
+		// Because other libraries might be sending them in this format.
+		deprecated := map[string][]string{}
+		if deprecatedErr := d.Decode(&deprecated); deprecatedErr == nil {
+			m = deprecatedArgs(deprecated)
+		} else {
+			return NewArgs(), err
+		}
 	}
-	return args, nil
+	return Args{m}, nil
+}
+
+// Get returns the list of values associates with a field.
+// It returns a slice of strings to keep backwards compatibility with old code.
+func (filters Args) Get(field string) []string {
+	values := filters.fields[field]
+	if values == nil {
+		return make([]string, 0)
+	}
+	slice := make([]string, 0, len(values))
+	for key := range values {
+		slice = append(slice, key)
+	}
+	return slice
+}
+
+// Add adds a new value to a filter field.
+func (filters Args) Add(name, value string) {
+	if _, ok := filters.fields[name]; ok {
+		filters.fields[name][value] = true
+	} else {
+		filters.fields[name] = map[string]bool{value: true}
+	}
+}
+
+// Del removes a value from a filter field.
+func (filters Args) Del(name, value string) {
+	if _, ok := filters.fields[name]; ok {
+		delete(filters.fields[name], value)
+	}
+}
+
+// Len returns the number of fields in the arguments.
+func (filters Args) Len() int {
+	return len(filters.fields)
 }
 
 // MatchKVList returns true if the values for the specified field maches the ones
 // from the sources.
 // e.g. given Args are {'label': {'label1=1','label2=1'}, 'image.name', {'ubuntu'}},
-//      field is 'label' and sources are {'label':{'label1=1','label2=2','label3=3'}}
+//      field is 'label' and sources are {'label1': '1', 'label2': '2'}
 //      it returns true.
 func (filters Args) MatchKVList(field string, sources map[string]string) bool {
-	fieldValues := filters[field]
+	fieldValues := filters.fields[field]
 
 	//do not filter if there is no filter set or cannot determine filter
 	if len(fieldValues) == 0 {
@@ -90,21 +145,16 @@ func (filters Args) MatchKVList(field string, sources map[string]string) bool {
 		return false
 	}
 
-outer:
-	for _, name2match := range fieldValues {
+	for name2match := range fieldValues {
 		testKV := strings.SplitN(name2match, "=", 2)
 
-		for k, v := range sources {
-			if len(testKV) == 1 {
-				if k == testKV[0] {
-					continue outer
-				}
-			} else if k == testKV[0] && v == testKV[1] {
-				continue outer
-			}
+		v, ok := sources[testKV[0]]
+		if !ok {
+			return false
+		}
+		if len(testKV) == 2 && testKV[1] != v {
+			return false
 		}
-
-		return false
 	}
 
 	return true
@@ -115,13 +165,12 @@ outer:
 //      field is 'image.name' and source is 'ubuntu'
 //      it returns true.
 func (filters Args) Match(field, source string) bool {
-	fieldValues := filters[field]
-
-	//do not filter if there is no filter set or cannot determine filter
-	if len(fieldValues) == 0 {
+	if filters.ExactMatch(field, source) {
 		return true
 	}
-	for _, name2match := range fieldValues {
+
+	fieldValues := filters.fields[field]
+	for name2match := range fieldValues {
 		match, err := regexp.MatchString(name2match, source)
 		if err != nil {
 			continue
@@ -132,3 +181,61 @@ func (filters Args) Match(field, source string) bool {
 	}
 	return false
 }
+
+// ExactMatch returns true if the source matches exactly one of the filters.
+func (filters Args) ExactMatch(field, source string) bool {
+	fieldValues, ok := filters.fields[field]
+	//do not filter if there is no filter set or cannot determine filter
+	if !ok || len(fieldValues) == 0 {
+		return true
+	}
+
+	// try to march full name value to avoid O(N) regular expression matching
+	if fieldValues[source] {
+		return true
+	}
+	return false
+}
+
+// Include returns true if the name of the field to filter is in the filters.
+func (filters Args) Include(field string) bool {
+	_, ok := filters.fields[field]
+	return ok
+}
+
+// Validate ensures that all the fields in the filter are valid.
+// It returns an error as soon as it finds an invalid field.
+func (filters Args) Validate(accepted map[string]bool) error {
+	for name := range filters.fields {
+		if !accepted[name] {
+			return fmt.Errorf("Invalid filter '%s'", name)
+		}
+	}
+	return nil
+}
+
+// WalkValues iterates over the list of filtered values for a field.
+// It stops the iteration if it finds an error and it returns that error.
+func (filters Args) WalkValues(field string, op func(value string) error) error {
+	if _, ok := filters.fields[field]; !ok {
+		return nil
+	}
+	for v := range filters.fields[field] {
+		if err := op(v); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func deprecatedArgs(d map[string][]string) map[string]map[string]bool {
+	m := map[string]map[string]bool{}
+	for k, v := range d {
+		values := map[string]bool{}
+		for _, vv := range v {
+			values[vv] = true
+		}
+		m[k] = values
+	}
+	return m
+}
diff --git a/parsers/filters/parse_test.go b/parsers/filters/parse_test.go
index eb9fcef..308d1bc 100644
--- a/parsers/filters/parse_test.go
+++ b/parsers/filters/parse_test.go
@@ -1,7 +1,7 @@
 package filters
 
 import (
-	"sort"
+	"fmt"
 	"testing"
 )
 
@@ -13,7 +13,7 @@ func TestParseArgs(t *testing.T) {
 		"image.name=*untu",
 	}
 	var (
-		args = Args{}
+		args = NewArgs()
 		err  error
 	)
 	for i := range flagArgs {
@@ -22,10 +22,10 @@ func TestParseArgs(t *testing.T) {
 			t.Errorf("failed to parse %s: %s", flagArgs[i], err)
 		}
 	}
-	if len(args["created"]) != 1 {
+	if len(args.Get("created")) != 1 {
 		t.Errorf("failed to set this arg")
 	}
-	if len(args["image.name"]) != 2 {
+	if len(args.Get("image.name")) != 2 {
 		t.Errorf("the args should have collapsed")
 	}
 }
@@ -36,7 +36,7 @@ func TestParseArgsEdgeCase(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if args == nil || len(args) != 0 {
+	if args.Len() != 0 {
 		t.Fatalf("Expected an empty Args (map), got %v", args)
 	}
 	if args, err = ParseFlag("anything", args); err == nil || err != ErrBadFormat {
@@ -45,10 +45,11 @@ func TestParseArgsEdgeCase(t *testing.T) {
 }
 
 func TestToParam(t *testing.T) {
-	a := Args{
-		"created":    []string{"today"},
-		"image.name": []string{"ubuntu*", "*untu"},
+	fields := map[string]map[string]bool{
+		"created":    {"today": true},
+		"image.name": {"ubuntu*": true, "*untu": true},
 	}
+	a := Args{fields: fields}
 
 	_, err := ToParam(a)
 	if err != nil {
@@ -63,42 +64,48 @@ func TestFromParam(t *testing.T) {
 		"{'key': 'value'}",
 		`{"key": "value"}`,
 	}
-	valids := map[string]Args{
-		`{"key": ["value"]}`: {
-			"key": {"value"},
+	valid := map[*Args][]string{
+		&Args{fields: map[string]map[string]bool{"key": {"value": true}}}: {
+			`{"key": ["value"]}`,
+			`{"key": {"value": true}}`,
 		},
-		`{"key": ["value1", "value2"]}`: {
-			"key": {"value1", "value2"},
+		&Args{fields: map[string]map[string]bool{"key": {"value1": true, "value2": true}}}: {
+			`{"key": ["value1", "value2"]}`,
+			`{"key": {"value1": true, "value2": true}}`,
 		},
-		`{"key1": ["value1"], "key2": ["value2"]}`: {
-			"key1": {"value1"},
-			"key2": {"value2"},
+		&Args{fields: map[string]map[string]bool{"key1": {"value1": true}, "key2": {"value2": true}}}: {
+			`{"key1": ["value1"], "key2": ["value2"]}`,
+			`{"key1": {"value1": true}, "key2": {"value2": true}}`,
 		},
 	}
+
 	for _, invalid := range invalids {
 		if _, err := FromParam(invalid); err == nil {
 			t.Fatalf("Expected an error with %v, got nothing", invalid)
 		}
 	}
-	for json, expectedArgs := range valids {
-		args, err := FromParam(json)
-		if err != nil {
-			t.Fatal(err)
-		}
-		if len(args) != len(expectedArgs) {
-			t.Fatalf("Expected %v, go %v", expectedArgs, args)
-		}
-		for key, expectedValues := range expectedArgs {
-			values := args[key]
-			sort.Strings(values)
-			sort.Strings(expectedValues)
-			if len(values) != len(expectedValues) {
+
+	for expectedArgs, matchers := range valid {
+		for _, json := range matchers {
+			args, err := FromParam(json)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if args.Len() != expectedArgs.Len() {
 				t.Fatalf("Expected %v, go %v", expectedArgs, args)
 			}
-			for index, expectedValue := range expectedValues {
-				if values[index] != expectedValue {
+			for key, expectedValues := range expectedArgs.fields {
+				values := args.Get(key)
+
+				if len(values) != len(expectedValues) {
 					t.Fatalf("Expected %v, go %v", expectedArgs, args)
 				}
+
+				for _, v := range values {
+					if !expectedValues[v] {
+						t.Fatalf("Expected %v, go %v", expectedArgs, args)
+					}
+				}
 			}
 		}
 	}
@@ -114,54 +121,63 @@ func TestEmpty(t *testing.T) {
 	if err != nil {
 		t.Errorf("%s", err)
 	}
-	if len(a) != len(v1) {
+	if a.Len() != v1.Len() {
 		t.Errorf("these should both be empty sets")
 	}
 }
 
-func TestArgsMatchKVList(t *testing.T) {
-	// empty sources
-	args := Args{
-		"created": []string{"today"},
+func TestArgsMatchKVListEmptySources(t *testing.T) {
+	args := NewArgs()
+	if !args.MatchKVList("created", map[string]string{}) {
+		t.Fatalf("Expected true for (%v,created), got true", args)
 	}
+
+	args = Args{map[string]map[string]bool{"created": {"today": true}}}
 	if args.MatchKVList("created", map[string]string{}) {
 		t.Fatalf("Expected false for (%v,created), got true", args)
 	}
+}
+
+func TestArgsMatchKVList(t *testing.T) {
 	// Not empty sources
 	sources := map[string]string{
 		"key1": "value1",
 		"key2": "value2",
 		"key3": "value3",
 	}
+
 	matches := map[*Args]string{
 		&Args{}: "field",
-		&Args{
-			"created": []string{"today"},
-			"labels":  []string{"key1"},
+		&Args{map[string]map[string]bool{
+			"created": map[string]bool{"today": true},
+			"labels":  map[string]bool{"key1": true}},
 		}: "labels",
-		&Args{
-			"created": []string{"today"},
-			"labels":  []string{"key1=value1"},
-		}: "labels",
-	}
-	differs := map[*Args]string{
-		&Args{
-			"created": []string{"today"},
-		}: "created",
-		&Args{
-			"created": []string{"today"},
-			"labels":  []string{"key4"},
-		}: "labels",
-		&Args{
-			"created": []string{"today"},
-			"labels":  []string{"key1=value3"},
+		&Args{map[string]map[string]bool{
+			"created": map[string]bool{"today": true},
+			"labels":  map[string]bool{"key1=value1": true}},
 		}: "labels",
 	}
+
 	for args, field := range matches {
 		if args.MatchKVList(field, sources) != true {
 			t.Fatalf("Expected true for %v on %v, got false", sources, args)
 		}
 	}
+
+	differs := map[*Args]string{
+		&Args{map[string]map[string]bool{
+			"created": map[string]bool{"today": true}},
+		}: "created",
+		&Args{map[string]map[string]bool{
+			"created": map[string]bool{"today": true},
+			"labels":  map[string]bool{"key4": true}},
+		}: "labels",
+		&Args{map[string]map[string]bool{
+			"created": map[string]bool{"today": true},
+			"labels":  map[string]bool{"key1=value3": true}},
+		}: "labels",
+	}
+
 	for args, field := range differs {
 		if args.MatchKVList(field, sources) != false {
 			t.Fatalf("Expected false for %v on %v, got true", sources, args)
@@ -171,48 +187,165 @@ func TestArgsMatchKVList(t *testing.T) {
 
 func TestArgsMatch(t *testing.T) {
 	source := "today"
+
 	matches := map[*Args]string{
 		&Args{}: "field",
-		&Args{
-			"created": []string{"today"},
-			"labels":  []string{"key1"},
+		&Args{map[string]map[string]bool{
+			"created": map[string]bool{"today": true}},
 		}: "today",
-		&Args{
-			"created": []string{"to*"},
+		&Args{map[string]map[string]bool{
+			"created": map[string]bool{"to*": true}},
 		}: "created",
-		&Args{
-			"created": []string{"to(.*)"},
+		&Args{map[string]map[string]bool{
+			"created": map[string]bool{"to(.*)": true}},
 		}: "created",
-		&Args{
-			"created": []string{"tod"},
+		&Args{map[string]map[string]bool{
+			"created": map[string]bool{"tod": true}},
 		}: "created",
-		&Args{
-			"created": []string{"anything", "to*"},
-		}: "created",
-	}
-	differs := map[*Args]string{
-		&Args{
-			"created": []string{"tomorrow"},
-		}: "created",
-		&Args{
-			"created": []string{"to(day"},
-		}: "created",
-		&Args{
-			"created": []string{"tom(.*)"},
-		}: "created",
-		&Args{
-			"created": []string{"today1"},
-			"labels":  []string{"today"},
+		&Args{map[string]map[string]bool{
+			"created": map[string]bool{"anyting": true, "to*": true}},
 		}: "created",
 	}
+
 	for args, field := range matches {
 		if args.Match(field, source) != true {
 			t.Fatalf("Expected true for %v on %v, got false", source, args)
 		}
 	}
+
+	differs := map[*Args]string{
+		&Args{map[string]map[string]bool{
+			"created": map[string]bool{"tomorrow": true}},
+		}: "created",
+		&Args{map[string]map[string]bool{
+			"created": map[string]bool{"to(day": true}},
+		}: "created",
+		&Args{map[string]map[string]bool{
+			"created": map[string]bool{"tom(.*)": true}},
+		}: "created",
+		&Args{map[string]map[string]bool{
+			"created": map[string]bool{"tom": true}},
+		}: "created",
+		&Args{map[string]map[string]bool{
+			"created": map[string]bool{"today1": true},
+			"labels":  map[string]bool{"today": true}},
+		}: "created",
+	}
+
 	for args, field := range differs {
 		if args.Match(field, source) != false {
 			t.Fatalf("Expected false for %v on %v, got true", source, args)
 		}
 	}
 }
+
+func TestAdd(t *testing.T) {
+	f := NewArgs()
+	f.Add("status", "running")
+	v := f.fields["status"]
+	if len(v) != 1 || !v["running"] {
+		t.Fatalf("Expected to include a running status, got %v", v)
+	}
+
+	f.Add("status", "paused")
+	if len(v) != 2 || !v["paused"] {
+		t.Fatalf("Expected to include a paused status, got %v", v)
+	}
+}
+
+func TestDel(t *testing.T) {
+	f := NewArgs()
+	f.Add("status", "running")
+	f.Del("status", "running")
+	v := f.fields["status"]
+	if v["running"] {
+		t.Fatalf("Expected to not include a running status filter, got true")
+	}
+}
+
+func TestLen(t *testing.T) {
+	f := NewArgs()
+	if f.Len() != 0 {
+		t.Fatalf("Expected to not include any field")
+	}
+	f.Add("status", "running")
+	if f.Len() != 1 {
+		t.Fatalf("Expected to include one field")
+	}
+}
+
+func TestExactMatch(t *testing.T) {
+	f := NewArgs()
+
+	if !f.ExactMatch("status", "running") {
+		t.Fatalf("Expected to match `running` when there are no filters, got false")
+	}
+
+	f.Add("status", "running")
+	f.Add("status", "pause*")
+
+	if !f.ExactMatch("status", "running") {
+		t.Fatalf("Expected to match `running` with one of the filters, got false")
+	}
+
+	if f.ExactMatch("status", "paused") {
+		t.Fatalf("Expected to not match `paused` with one of the filters, got true")
+	}
+}
+
+func TestInclude(t *testing.T) {
+	f := NewArgs()
+	if f.Include("status") {
+		t.Fatalf("Expected to not include a status key, got true")
+	}
+	f.Add("status", "running")
+	if !f.Include("status") {
+		t.Fatalf("Expected to include a status key, got false")
+	}
+}
+
+func TestValidate(t *testing.T) {
+	f := NewArgs()
+	f.Add("status", "running")
+
+	valid := map[string]bool{
+		"status":   true,
+		"dangling": true,
+	}
+
+	if err := f.Validate(valid); err != nil {
+		t.Fatal(err)
+	}
+
+	f.Add("bogus", "running")
+	if err := f.Validate(valid); err == nil {
+		t.Fatalf("Expected to return an error, got nil")
+	}
+}
+
+func TestWalkValues(t *testing.T) {
+	f := NewArgs()
+	f.Add("status", "running")
+	f.Add("status", "paused")
+
+	f.WalkValues("status", func(value string) error {
+		if value != "running" && value != "paused" {
+			t.Fatalf("Unexpected value %s", value)
+		}
+		return nil
+	})
+
+	err := f.WalkValues("status", func(value string) error {
+		return fmt.Errorf("return")
+	})
+	if err == nil {
+		t.Fatalf("Expected to get an error, got nil")
+	}
+
+	err = f.WalkValues("foo", func(value string) error {
+		return fmt.Errorf("return")
+	})
+	if err != nil {
+		t.Fatalf("Expected to not iterate when the field doesn't exist, got %v", err)
+	}
+}
diff --git a/pubsub/publisher.go b/pubsub/publisher.go
index ab457cf..8529ffa 100644
--- a/pubsub/publisher.go
+++ b/pubsub/publisher.go
@@ -13,11 +13,12 @@ func NewPublisher(publishTimeout time.Duration, buffer int) *Publisher {
 	return &Publisher{
 		buffer:      buffer,
 		timeout:     publishTimeout,
-		subscribers: make(map[subscriber]struct{}),
+		subscribers: make(map[subscriber]topicFunc),
 	}
 }
 
 type subscriber chan interface{}
+type topicFunc func(v interface{}) bool
 
 // Publisher is basic pub/sub structure. Allows to send events and subscribe
 // to them. Can be safely used from multiple goroutines.
@@ -25,7 +26,7 @@ type Publisher struct {
 	m           sync.RWMutex
 	buffer      int
 	timeout     time.Duration
-	subscribers map[subscriber]struct{}
+	subscribers map[subscriber]topicFunc
 }
 
 // Len returns the number of subscribers for the publisher
@@ -38,9 +39,14 @@ func (p *Publisher) Len() int {
 
 // Subscribe adds a new subscriber to the publisher returning the channel.
 func (p *Publisher) Subscribe() chan interface{} {
+	return p.SubscribeTopic(nil)
+}
+
+// SubscribeTopic adds a new subscriber that filters messages sent by a topic.
+func (p *Publisher) SubscribeTopic(topic topicFunc) chan interface{} {
 	ch := make(chan interface{}, p.buffer)
 	p.m.Lock()
-	p.subscribers[ch] = struct{}{}
+	p.subscribers[ch] = topic
 	p.m.Unlock()
 	return ch
 }
@@ -56,20 +62,13 @@ func (p *Publisher) Evict(sub chan interface{}) {
 // Publish sends the data in v to all subscribers currently registered with the publisher.
 func (p *Publisher) Publish(v interface{}) {
 	p.m.RLock()
-	for sub := range p.subscribers {
-		// send under a select as to not block if the receiver is unavailable
-		if p.timeout > 0 {
-			select {
-			case sub <- v:
-			case <-time.After(p.timeout):
-			}
-			continue
-		}
-		select {
-		case sub <- v:
-		default:
-		}
+	wg := new(sync.WaitGroup)
+	for sub, topic := range p.subscribers {
+		wg.Add(1)
+
+		go p.sendTopic(sub, topic, v, wg)
 	}
+	wg.Wait()
 	p.m.RUnlock()
 }
 
@@ -82,3 +81,24 @@ func (p *Publisher) Close() {
 	}
 	p.m.Unlock()
 }
+
+func (p *Publisher) sendTopic(sub subscriber, topic topicFunc, v interface{}, wg *sync.WaitGroup) {
+	defer wg.Done()
+	if topic != nil && !topic(v) {
+		return
+	}
+
+	// send under a select as to not block if the receiver is unavailable
+	if p.timeout > 0 {
+		select {
+		case sub <- v:
+		case <-time.After(p.timeout):
+		}
+		return
+	}
+
+	select {
+	case sub <- v:
+	default:
+	}
+}