diff --git a/constants.go b/constants.go
index 72bdafa..db22014 100644
--- a/constants.go
+++ b/constants.go
@@ -208,7 +208,7 @@ const (
 	TagUnsupportedValue      = 0x10
 	TagDefault               = 0x11
 	TagUnknown               = 0x12
-	TagNoValue               = 0x013
+	TagNoValue               = 0x13
 	TagNotSettable           = 0x15
 	TagDeleteAttr            = 0x16
 	TagAdminDefine           = 0x17
@@ -300,88 +300,112 @@ const (
 )
 
 const (
-	OperationAttributeCopies              string = "copies"
-	OperationAttributeDocumentFormat             = "document-format"
-	OperationAttributeDocumentName               = "document-name"
-	OperationAttributeJobID                      = "job-id"
-	OperationAttributeJobName                    = "job-name"
-	OperationAttributeJobPriority                = "job-priority"
-	OperationAttributeJobURI                     = "job-uri"
-	OperationAttributeLastDocument               = "last-document"
-	OperationAttributeMyJobs                     = "my-jobs"
-	OperationAttributePPDName                    = "ppd-name"
-	OperationAttributePrinterIsShared            = "printer-is-shared"
-	OperationAttributePrinterURI                 = "printer-uri"
-	OperationAttributePurgeJobs                  = "purge-jobs"
-	OperationAttributeRequestedAttributes        = "requested-attributes"
-	OperationAttributeRequestingUserName         = "requesting-user-name"
-	OperationAttributeWhichJobs                  = "which-jobs"
-	OperationAttributeFirstJobID                 = "first-job-id"
-	OperationAttributeLimit                      = "limit"
-)
-
-const (
-	PrinterAttributeDeviceURI          string = "device-uri"
-	PrinterAttributeHoldJobUntil              = "job-hold-until"
-	PrinterAttributePrinterErrorPolicy        = "printer-error-policy"
-	PrinterAttributePrinterInfo               = "printer-info"
-	PrinterAttributePrinterLocation           = "printer-location"
-	PrinterAttributePrinterName               = "printer-name"
-	PrinterAttributePrinterStateReason        = "printer-state-reason"
-	PrinterAttributeJobPrinterURI             = "job-printer-uri"
-	PrinterAttributeMemberURIs                = "member-uris"
+	AttributeCopies                 string = "copies"
+	AttributeDocumentFormat                = "document-format"
+	AttributeDocumentName                  = "document-name"
+	AttributeJobID                         = "job-id"
+	AttributeJobName                       = "job-name"
+	AttributeJobPriority                   = "job-priority"
+	AttributeJobURI                        = "job-uri"
+	AttributeLastDocument                  = "last-document"
+	AttributeMyJobs                        = "my-jobs"
+	AttributePPDName                       = "ppd-name"
+	AttributePrinterIsShared               = "printer-is-shared"
+	AttributePrinterURI                    = "printer-uri"
+	AttributePurgeJobs                     = "purge-jobs"
+	AttributeRequestedAttributes           = "requested-attributes"
+	AttributeRequestingUserName            = "requesting-user-name"
+	AttributeWhichJobs                     = "which-jobs"
+	AttributeFirstJobID                    = "first-job-id"
+	AttributeLimit                         = "limit"
+	AttributeStatusMessage                 = "status-message"
+	AttributeCharset                       = "attributes-charset"
+	AttributeNaturalLanguage               = "attributes-natural-language"
+	AttributeDeviceURI                     = "device-uri"
+	AttributeHoldJobUntil                  = "job-hold-until"
+	AttributePrinterErrorPolicy            = "printer-error-policy"
+	AttributePrinterInfo                   = "printer-info"
+	AttributePrinterLocation               = "printer-location"
+	AttributePrinterName                   = "printer-name"
+	AttributePrinterStateReason            = "printer-state-reason"
+	AttributeJobPrinterURI                 = "job-printer-uri"
+	AttributeMemberURIs                    = "member-uris"
+	AttributeDocumentNumber                = "document-number"
+	AttributeDocumentState                 = "document-state"
+	AttributeFinishings                    = "finishings"
+	AttributeJobHoldUntil                  = "hold-job-until"
+	AttributeJobSheets                     = "job-sheets"
+	AttributeJobState                      = "job-state"
+	AttributeJobStateReason                = "job-state-reason"
+	AttributeMedia                         = "media"
+	AttributeNumberUp                      = "number-up"
+	AttributeOrientationRequested          = "orientation-requested"
+	AttributePrintQuality                  = "print-quality"
+	AttributePrinterIsAcceptingJobs        = "printer-is-accepting-jobs"
+	AttributePrinterResolution             = "printer-resolution"
+	AttributePrinterState                  = "printer-state"
+	AttributeMemberNames                   = "member-names"
+	AttributePrinterType                   = "printer-type"
+	AttributePrinterMarkAndModel           = "printer-make-and-model"
+	AttributePrinterStateMessage           = "printer-state-message"
+	AttributePrinterUriSupported           = "printer-uri-supported"
+	AttributeJobMediaProgress              = "job-media-progress"
+	AttributeJobKilobyteOctets             = "job-k-octets"
+	AttributeNumberOfDocuments             = "number-of-documents"
+	AttributeJobOriginatingUserName        = "job-originating-user-name"
 )
 
 var (
-	DefaultClassAttributes   = []string{"printer-name", "member-names"}
-	DefaultPrinterAttributes = []string{"printer-name", "printer-type", "printer-location", "printer-info",
-		"printer-make-and-model", "printer-state", "printer-state-message", "printer-state-reason",
-		"printer-uri-supported", "device-uri", "printer-is-shared"}
-	DefaultJobAttributes = []string{"job-id", "job-name", "printer-uri", "job-state", "job-state-reasons",
-		"job-hold-until", "job-media-progress", "job-k-octets", "number-of-documents", "copies",
-		"job-originating-user-name"}
+	DefaultClassAttributes   = []string{AttributePrinterName, AttributeMemberNames}
+	DefaultPrinterAttributes = []string{AttributePrinterName, AttributePrinterType, AttributePrinterLocation, AttributePrinterInfo,
+		AttributePrinterMarkAndModel, AttributePrinterState, AttributePrinterStateMessage, AttributePrinterStateReason,
+		AttributePrinterUriSupported, AttributeDeviceURI, AttributePrinterIsShared}
+	DefaultJobAttributes = []string{AttributeJobID, AttributeJobName, AttributePrinterURI, AttributeJobState, AttributeJobStateReason,
+		AttributeJobHoldUntil, AttributeJobMediaProgress, AttributeJobKilobyteOctets, AttributeNumberOfDocuments, AttributeCopies,
+		AttributeJobOriginatingUserName}
 
 	AttributeTagMapping = map[string]Tag{
-		"attributes-charset":          TagCharset,
-		"attributes-natural-language": TagLanguage,
-		"copies":                      TagInteger,
-		"device-uri":                  TagUri,
-		"document-format":             TagMimeType,
-		"document-name":               TagName,
-		"document-number":             TagInteger,
-		"document-state":              TagEnum,
-		"finishings":                  TagEnum,
-		"hold-job-until":              TagKeyword,
-		"job-hold-until":              TagKeyword,
-		"job-id":                      TagInteger,
-		"job-name":                    TagName,
-		"job-printer-uri":             TagUri,
-		"job-priority":                TagInteger,
-		"job-sheets":                  TagName,
-		"job-state":                   TagEnum,
-		"job-state-reason":            TagKeyword,
-		"job-uri":                     TagUri,
-		"last-document":               TagBoolean,
-		"media":                       TagKeyword,
-		"member-uris":                 TagUri,
-		"my-jobs":                     TagBoolean,
-		"number-up":                   TagInteger,
-		"orientation-requested":       TagEnum,
-		"ppd-name":                    TagName,
-		"print-quality":               TagEnum,
-		"printer-error-policy":        TagName,
-		"printer-info":                TagText,
-		"printer-is-accepting-jobs":   TagBoolean,
-		"printer-is-shared":           TagBoolean,
-		"printer-location":            TagText,
-		"printer-resolution":          TagResolution,
-		"printer-state":               TagEnum,
-		"printer-state-reason":        TagKeyword,
-		"printer-uri":                 TagUri,
-		"purge-jobs":                  TagBoolean,
-		"requested-attributes":        TagKeyword,
-		"requesting-user-name":        TagName,
-		"which-jobs":                  TagKeyword,
-		"first-job-id":                TagInteger,
+		AttributeCharset:                TagCharset,
+		AttributeNaturalLanguage:        TagLanguage,
+		AttributeCopies:                 TagInteger,
+		AttributeDeviceURI:              TagUri,
+		AttributeDocumentFormat:         TagMimeType,
+		AttributeDocumentName:           TagName,
+		AttributeDocumentNumber:         TagInteger,
+		AttributeDocumentState:          TagEnum,
+		AttributeFinishings:             TagEnum,
+		AttributeJobHoldUntil:           TagKeyword,
+		AttributeHoldJobUntil:           TagKeyword,
+		AttributeJobID:                  TagInteger,
+		AttributeJobName:                TagName,
+		AttributeJobPrinterURI:          TagUri,
+		AttributeJobPriority:            TagInteger,
+		AttributeJobSheets:              TagName,
+		AttributeJobState:               TagEnum,
+		AttributeJobStateReason:         TagKeyword,
+		AttributeJobURI:                 TagUri,
+		AttributeLastDocument:           TagBoolean,
+		AttributeMedia:                  TagKeyword,
+		AttributeMemberURIs:             TagUri,
+		AttributeMyJobs:                 TagBoolean,
+		AttributeNumberUp:               TagInteger,
+		AttributeOrientationRequested:   TagEnum,
+		AttributePPDName:                TagName,
+		AttributePrintQuality:           TagEnum,
+		AttributePrinterErrorPolicy:     TagName,
+		AttributePrinterInfo:            TagText,
+		AttributePrinterIsAcceptingJobs: TagBoolean,
+		AttributePrinterIsShared:        TagBoolean,
+		AttributePrinterLocation:        TagText,
+		AttributePrinterResolution:      TagResolution,
+		AttributePrinterState:           TagEnum,
+		AttributePrinterStateReason:     TagKeyword,
+		AttributePrinterURI:             TagUri,
+		AttributePurgeJobs:              TagBoolean,
+		AttributeRequestedAttributes:    TagKeyword,
+		AttributeRequestingUserName:     TagName,
+		AttributeWhichJobs:              TagKeyword,
+		AttributeFirstJobID:             TagInteger,
+		AttributeStatusMessage:          TagText,
 	}
 )
diff --git a/cups-client.go b/cups-client.go
index f90d090..a59b807 100644
--- a/cups-client.go
+++ b/cups-client.go
@@ -22,7 +22,7 @@ func (c *CUPSClient) GetDevices() (map[string]Attributes, error) {
 	printerNameMap := make(map[string]Attributes)
 
 	for _, printerAttributes := range resp.PrinterAttributes {
-		printerNameMap[printerAttributes[PrinterAttributeDeviceURI][0].Value.(string)] = printerAttributes
+		printerNameMap[printerAttributes[AttributeDeviceURI][0].Value.(string)] = printerAttributes
 	}
 
 	return printerNameMap, nil
@@ -30,8 +30,8 @@ func (c *CUPSClient) GetDevices() (map[string]Attributes, error) {
 
 func (c *CUPSClient) MoveJob(jobID int, destPrinter string) error {
 	req := NewRequest(OperationCupsMoveJob, 1)
-	req.OperationAttributes[OperationAttributeJobURI] = c.getJobUri(jobID)
-	req.PrinterAttributes[PrinterAttributeJobPrinterURI] = c.getPrinterUri(destPrinter)
+	req.OperationAttributes[AttributeJobURI] = c.getJobUri(jobID)
+	req.PrinterAttributes[AttributeJobPrinterURI] = c.getPrinterUri(destPrinter)
 
 	_, err := c.SendRequest(c.getHttpUri("jobs", ""), req, nil)
 	return err
@@ -39,8 +39,8 @@ func (c *CUPSClient) MoveJob(jobID int, destPrinter string) error {
 
 func (c *CUPSClient) MoveAllJob(srcPrinter, destPrinter string) error {
 	req := NewRequest(OperationCupsMoveJob, 1)
-	req.OperationAttributes[OperationAttributePrinterURI] = c.getPrinterUri(srcPrinter)
-	req.PrinterAttributes[PrinterAttributeJobPrinterURI] = c.getPrinterUri(destPrinter)
+	req.OperationAttributes[AttributePrinterURI] = c.getPrinterUri(srcPrinter)
+	req.PrinterAttributes[AttributeJobPrinterURI] = c.getPrinterUri(destPrinter)
 
 	_, err := c.SendRequest(c.getHttpUri("jobs", ""), req, nil)
 	return err
@@ -57,7 +57,7 @@ func (c *CUPSClient) GetPPDs() (map[string]Attributes, error) {
 	ppdNameMap := make(map[string]Attributes)
 
 	for _, printerAttributes := range resp.PrinterAttributes {
-		ppdNameMap[printerAttributes[OperationAttributePPDName][0].Value.(string)] = printerAttributes
+		ppdNameMap[printerAttributes[AttributePPDName][0].Value.(string)] = printerAttributes
 	}
 
 	return ppdNameMap, nil
@@ -65,7 +65,7 @@ func (c *CUPSClient) GetPPDs() (map[string]Attributes, error) {
 
 func (c *CUPSClient) AcceptJobs(printer string) error {
 	req := NewRequest(OperationCupsAcceptJobs, 1)
-	req.OperationAttributes[OperationAttributePrinterURI] = c.getPrinterUri(printer)
+	req.OperationAttributes[AttributePrinterURI] = c.getPrinterUri(printer)
 
 	_, err := c.SendRequest(c.getHttpUri("admin", ""), req, nil)
 	return err
@@ -73,14 +73,14 @@ func (c *CUPSClient) AcceptJobs(printer string) error {
 
 func (c *CUPSClient) RejectJobs(printer string) error {
 	req := NewRequest(OperationCupsRejectJobs, 1)
-	req.OperationAttributes[OperationAttributePrinterURI] = c.getPrinterUri(printer)
+	req.OperationAttributes[AttributePrinterURI] = c.getPrinterUri(printer)
 
 	_, err := c.SendRequest(c.getHttpUri("admin", ""), req, nil)
 	return err
 }
 
 func (c *CUPSClient) AddPrinterToClass(class, printer string) error {
-	attributes, err := c.GetPrinterAttributes(class, []string{PrinterAttributeMemberURIs})
+	attributes, err := c.GetPrinterAttributes(class, []string{AttributeMemberURIs})
 	if err != nil && !IsNotExistsError(err) {
 		return err
 	}
@@ -88,7 +88,7 @@ func (c *CUPSClient) AddPrinterToClass(class, printer string) error {
 	memberURIList := make([]string, 0)
 
 	if !IsNotExistsError(err) {
-		for _, member := range attributes[PrinterAttributeMemberURIs] {
+		for _, member := range attributes[AttributeMemberURIs] {
 			memberString := strings.Split(member.Value.(string), "/")
 			printerName := memberString[len(memberString)-1]
 
@@ -103,22 +103,22 @@ func (c *CUPSClient) AddPrinterToClass(class, printer string) error {
 	memberURIList = append(memberURIList, c.getPrinterUri(printer))
 
 	req := NewRequest(OperationCupsAddModifyClass, 1)
-	req.OperationAttributes[OperationAttributePrinterURI] = c.getClassUri(class)
-	req.PrinterAttributes[PrinterAttributeMemberURIs] = memberURIList
+	req.OperationAttributes[AttributePrinterURI] = c.getClassUri(class)
+	req.PrinterAttributes[AttributeMemberURIs] = memberURIList
 
 	_, err = c.SendRequest(c.getHttpUri("admin", ""), req, nil)
 	return err
 }
 
 func (c *CUPSClient) DeletePrinterFromClass(class, printer string) error {
-	attributes, err := c.GetPrinterAttributes(class, []string{PrinterAttributeMemberURIs})
+	attributes, err := c.GetPrinterAttributes(class, []string{AttributeMemberURIs})
 	if err != nil {
 		return err
 	}
 
 	memberURIList := make([]string, 0)
 
-	for _, member := range attributes[PrinterAttributeMemberURIs] {
+	for _, member := range attributes[AttributeMemberURIs] {
 		memberString := strings.Split(member.Value.(string), "/")
 		printerName := memberString[len(memberString)-1]
 
@@ -132,8 +132,8 @@ func (c *CUPSClient) DeletePrinterFromClass(class, printer string) error {
 	}
 
 	req := NewRequest(OperationCupsAddModifyClass, 1)
-	req.OperationAttributes[OperationAttributePrinterURI] = c.getClassUri(class)
-	req.PrinterAttributes[PrinterAttributeMemberURIs] = memberURIList
+	req.OperationAttributes[AttributePrinterURI] = c.getClassUri(class)
+	req.PrinterAttributes[AttributeMemberURIs] = memberURIList
 
 	_, err = c.SendRequest(c.getHttpUri("admin", ""), req, nil)
 	return err
@@ -141,7 +141,7 @@ func (c *CUPSClient) DeletePrinterFromClass(class, printer string) error {
 
 func (c *CUPSClient) DeleteClass(class string) error {
 	req := NewRequest(OperationCupsDeleteClass, 1)
-	req.OperationAttributes[OperationAttributePrinterURI] = c.getClassUri(class)
+	req.OperationAttributes[AttributePrinterURI] = c.getClassUri(class)
 
 	_, err := c.SendRequest(c.getHttpUri("admin", ""), req, nil)
 	return err
@@ -149,14 +149,14 @@ func (c *CUPSClient) DeleteClass(class string) error {
 
 func (c *CUPSClient) CreatePrinter(name, deviceURI, ppd string, shared bool, errorPolicy ErrorPolicy, information, location string) error {
 	req := NewRequest(OperationCupsAddModifyPrinter, 1)
-	req.OperationAttributes[OperationAttributePrinterURI] = c.getPrinterUri(name)
-	req.OperationAttributes[OperationAttributePPDName] = ppd
-	req.OperationAttributes[OperationAttributePrinterIsShared] = shared
-	req.PrinterAttributes[PrinterAttributePrinterStateReason] = "none"
-	req.PrinterAttributes[PrinterAttributeDeviceURI] = deviceURI
-	req.PrinterAttributes[PrinterAttributePrinterInfo] = information
-	req.PrinterAttributes[PrinterAttributePrinterLocation] = location
-	req.PrinterAttributes[PrinterAttributePrinterErrorPolicy] = string(errorPolicy)
+	req.OperationAttributes[AttributePrinterURI] = c.getPrinterUri(name)
+	req.OperationAttributes[AttributePPDName] = ppd
+	req.OperationAttributes[AttributePrinterIsShared] = shared
+	req.PrinterAttributes[AttributePrinterStateReason] = "none"
+	req.PrinterAttributes[AttributeDeviceURI] = deviceURI
+	req.PrinterAttributes[AttributePrinterInfo] = information
+	req.PrinterAttributes[AttributePrinterLocation] = location
+	req.PrinterAttributes[AttributePrinterErrorPolicy] = string(errorPolicy)
 
 	_, err := c.SendRequest(c.getHttpUri("admin", ""), req, nil)
 	return err
@@ -164,8 +164,8 @@ func (c *CUPSClient) CreatePrinter(name, deviceURI, ppd string, shared bool, err
 
 func (c *CUPSClient) SetPrinterPPD(printer, ppd string) error {
 	req := NewRequest(OperationCupsAddModifyPrinter, 1)
-	req.OperationAttributes[OperationAttributePrinterURI] = c.getPrinterUri(printer)
-	req.OperationAttributes[OperationAttributePPDName] = ppd
+	req.OperationAttributes[AttributePrinterURI] = c.getPrinterUri(printer)
+	req.OperationAttributes[AttributePPDName] = ppd
 
 	_, err := c.SendRequest(c.getHttpUri("admin", ""), req, nil)
 	return err
@@ -173,8 +173,8 @@ func (c *CUPSClient) SetPrinterPPD(printer, ppd string) error {
 
 func (c *CUPSClient) SetPrinterDeviceURI(printer, deviceURI string) error {
 	req := NewRequest(OperationCupsAddModifyPrinter, 1)
-	req.OperationAttributes[OperationAttributePrinterURI] = c.getPrinterUri(printer)
-	req.PrinterAttributes[PrinterAttributeDeviceURI] = deviceURI
+	req.OperationAttributes[AttributePrinterURI] = c.getPrinterUri(printer)
+	req.PrinterAttributes[AttributeDeviceURI] = deviceURI
 
 	_, err := c.SendRequest(c.getHttpUri("admin", ""), req, nil)
 	return err
@@ -182,8 +182,8 @@ func (c *CUPSClient) SetPrinterDeviceURI(printer, deviceURI string) error {
 
 func (c *CUPSClient) SetPrinterIsShared(printer string, shared bool) error {
 	req := NewRequest(OperationCupsAddModifyPrinter, 1)
-	req.OperationAttributes[OperationAttributePrinterURI] = c.getPrinterUri(printer)
-	req.OperationAttributes[OperationAttributePrinterIsShared] = shared
+	req.OperationAttributes[AttributePrinterURI] = c.getPrinterUri(printer)
+	req.OperationAttributes[AttributePrinterIsShared] = shared
 
 	_, err := c.SendRequest(c.getHttpUri("admin", ""), req, nil)
 	return err
@@ -191,8 +191,8 @@ func (c *CUPSClient) SetPrinterIsShared(printer string, shared bool) error {
 
 func (c *CUPSClient) SetPrinterErrorPolicy(printer string, errorPolicy ErrorPolicy) error {
 	req := NewRequest(OperationCupsAddModifyPrinter, 1)
-	req.OperationAttributes[OperationAttributePrinterURI] = c.getPrinterUri(printer)
-	req.PrinterAttributes[PrinterAttributePrinterErrorPolicy] = string(errorPolicy)
+	req.OperationAttributes[AttributePrinterURI] = c.getPrinterUri(printer)
+	req.PrinterAttributes[AttributePrinterErrorPolicy] = string(errorPolicy)
 
 	_, err := c.SendRequest(c.getHttpUri("admin", ""), req, nil)
 	return err
@@ -200,8 +200,8 @@ func (c *CUPSClient) SetPrinterErrorPolicy(printer string, errorPolicy ErrorPoli
 
 func (c *CUPSClient) SetPrinterInformation(printer, information string) error {
 	req := NewRequest(OperationCupsAddModifyPrinter, 1)
-	req.OperationAttributes[OperationAttributePrinterURI] = c.getPrinterUri(printer)
-	req.PrinterAttributes[PrinterAttributePrinterInfo] = information
+	req.OperationAttributes[AttributePrinterURI] = c.getPrinterUri(printer)
+	req.PrinterAttributes[AttributePrinterInfo] = information
 
 	_, err := c.SendRequest(c.getHttpUri("admin", ""), req, nil)
 	return err
@@ -209,8 +209,8 @@ func (c *CUPSClient) SetPrinterInformation(printer, information string) error {
 
 func (c *CUPSClient) SetPrinterLocation(printer, location string) error {
 	req := NewRequest(OperationCupsAddModifyPrinter, 1)
-	req.OperationAttributes[OperationAttributePrinterURI] = c.getPrinterUri(printer)
-	req.PrinterAttributes[PrinterAttributePrinterLocation] = location
+	req.OperationAttributes[AttributePrinterURI] = c.getPrinterUri(printer)
+	req.PrinterAttributes[AttributePrinterLocation] = location
 
 	_, err := c.SendRequest(c.getHttpUri("admin", ""), req, nil)
 	return err
@@ -218,7 +218,7 @@ func (c *CUPSClient) SetPrinterLocation(printer, location string) error {
 
 func (c *CUPSClient) DeletePrinter(printer string) error {
 	req := NewRequest(OperationCupsDeletePrinter, 1)
-	req.OperationAttributes[OperationAttributePrinterURI] = c.getPrinterUri(printer)
+	req.OperationAttributes[AttributePrinterURI] = c.getPrinterUri(printer)
 
 	_, err := c.SendRequest(c.getHttpUri("admin", ""), req, nil)
 	return err
@@ -228,9 +228,9 @@ func (c *CUPSClient) GetPrinters(attributes []string) (map[string]Attributes, er
 	req := NewRequest(OperationCupsGetPrinters, 1)
 
 	if attributes == nil {
-		req.OperationAttributes[OperationAttributeRequestedAttributes] = DefaultPrinterAttributes
+		req.OperationAttributes[AttributeRequestedAttributes] = DefaultPrinterAttributes
 	} else {
-		req.OperationAttributes[OperationAttributeRequestedAttributes] = append(attributes, PrinterAttributePrinterName)
+		req.OperationAttributes[AttributeRequestedAttributes] = append(attributes, AttributePrinterName)
 	}
 
 	resp, err := c.SendRequest(c.getHttpUri("", nil), req, nil)
@@ -241,7 +241,7 @@ func (c *CUPSClient) GetPrinters(attributes []string) (map[string]Attributes, er
 	printerNameMap := make(map[string]Attributes)
 
 	for _, printerAttributes := range resp.PrinterAttributes {
-		printerNameMap[printerAttributes[PrinterAttributePrinterName][0].Value.(string)] = printerAttributes
+		printerNameMap[printerAttributes[AttributePrinterName][0].Value.(string)] = printerAttributes
 	}
 
 	return printerNameMap, nil
@@ -251,9 +251,9 @@ func (c *CUPSClient) GetClasses(attributes []string) (map[string]Attributes, err
 	req := NewRequest(OperationCupsGetClasses, 1)
 
 	if attributes == nil {
-		req.OperationAttributes[OperationAttributeRequestedAttributes] = DefaultClassAttributes
+		req.OperationAttributes[AttributeRequestedAttributes] = DefaultClassAttributes
 	} else {
-		req.OperationAttributes[OperationAttributeRequestedAttributes] = append(attributes, PrinterAttributePrinterName)
+		req.OperationAttributes[AttributeRequestedAttributes] = append(attributes, AttributePrinterName)
 	}
 
 	resp, err := c.SendRequest(c.getHttpUri("", nil), req, nil)
@@ -264,7 +264,7 @@ func (c *CUPSClient) GetClasses(attributes []string) (map[string]Attributes, err
 	printerNameMap := make(map[string]Attributes)
 
 	for _, printerAttributes := range resp.PrinterAttributes {
-		printerNameMap[printerAttributes[PrinterAttributePrinterName][0].Value.(string)] = printerAttributes
+		printerNameMap[printerAttributes[AttributePrinterName][0].Value.(string)] = printerAttributes
 	}
 
 	return printerNameMap, nil
diff --git a/ipp-client.go b/ipp-client.go
index befeb89..483a00b 100644
--- a/ipp-client.go
+++ b/ipp-client.go
@@ -124,13 +124,13 @@ func (c *IPPClient) PrintDocuments(docs []Document, printer string, jobAttribute
 	printerURI := c.getPrinterUri(printer)
 
 	req := NewRequest(OperationCreateJob, 1)
-	req.OperationAttributes[OperationAttributePrinterURI] = printerURI
-	req.OperationAttributes[OperationAttributeRequestingUserName] = c.username
+	req.OperationAttributes[AttributePrinterURI] = printerURI
+	req.OperationAttributes[AttributeRequestingUserName] = c.username
 
 	// set defaults for some attributes, may get overwritten
-	req.OperationAttributes[OperationAttributeJobName] = docs[0].Name
-	req.OperationAttributes[OperationAttributeCopies] = 1
-	req.OperationAttributes[OperationAttributeJobPriority] = DefaultJobPriority
+	req.OperationAttributes[AttributeJobName] = docs[0].Name
+	req.OperationAttributes[AttributeCopies] = 1
+	req.OperationAttributes[AttributeJobPriority] = DefaultJobPriority
 
 	for key, value := range jobAttributes {
 		req.JobAttributes[key] = value
@@ -145,18 +145,18 @@ func (c *IPPClient) PrintDocuments(docs []Document, printer string, jobAttribute
 		return 0, errors.New("server doesn't returned a job id")
 	}
 
-	jobID := resp.JobAttributes[0][OperationAttributeJobID][0].Value.(int)
+	jobID := resp.JobAttributes[0][AttributeJobID][0].Value.(int)
 
 	documentCount := len(docs) - 1
 
 	for docID, doc := range docs {
 		req = NewRequest(OperationSendDocument, 2)
-		req.OperationAttributes[OperationAttributePrinterURI] = printerURI
-		req.OperationAttributes[OperationAttributeRequestingUserName] = c.username
-		req.OperationAttributes[OperationAttributeJobID] = jobID
-		req.OperationAttributes[OperationAttributeDocumentName] = doc.Name
-		req.OperationAttributes[OperationAttributeDocumentFormat] = doc.MimeType
-		req.OperationAttributes[OperationAttributeLastDocument] = docID == documentCount
+		req.OperationAttributes[AttributePrinterURI] = printerURI
+		req.OperationAttributes[AttributeRequestingUserName] = c.username
+		req.OperationAttributes[AttributeJobID] = jobID
+		req.OperationAttributes[AttributeDocumentName] = doc.Name
+		req.OperationAttributes[AttributeDocumentFormat] = doc.MimeType
+		req.OperationAttributes[AttributeLastDocument] = docID == documentCount
 		req.File = doc.Document
 		req.FileSize = doc.Size
 
@@ -190,14 +190,14 @@ func (c *IPPClient) PrintJob(doc Document, printer string, jobAttributes map[str
 	printerURI := c.getPrinterUri(printer)
 
 	req := NewRequest(OperationPrintJob, 1)
-	req.OperationAttributes[OperationAttributePrinterURI] = printerURI
-	req.OperationAttributes[OperationAttributeRequestingUserName] = c.username
-	req.OperationAttributes[OperationAttributeJobName] = doc.Name
-	req.OperationAttributes[OperationAttributeDocumentFormat] = doc.MimeType
+	req.OperationAttributes[AttributePrinterURI] = printerURI
+	req.OperationAttributes[AttributeRequestingUserName] = c.username
+	req.OperationAttributes[AttributeJobName] = doc.Name
+	req.OperationAttributes[AttributeDocumentFormat] = doc.MimeType
 
 	// set defaults for some attributes, may get overwritten
-	req.OperationAttributes[OperationAttributeCopies] = 1
-	req.OperationAttributes[OperationAttributeJobPriority] = DefaultJobPriority
+	req.OperationAttributes[AttributeCopies] = 1
+	req.OperationAttributes[AttributeJobPriority] = DefaultJobPriority
 
 	for key, value := range jobAttributes {
 		req.JobAttributes[key] = value
@@ -215,7 +215,7 @@ func (c *IPPClient) PrintJob(doc Document, printer string, jobAttributes map[str
 		return 0, errors.New("server doesn't returned a job id")
 	}
 
-	jobID := resp.JobAttributes[0][OperationAttributeJobID][0].Value.(int)
+	jobID := resp.JobAttributes[0][AttributeJobID][0].Value.(int)
 
 	return jobID, nil
 }
@@ -234,7 +234,7 @@ func (c *IPPClient) PrintFile(filePath, printer string, jobAttributes map[string
 	}
 	defer document.Close()
 
-	jobAttributes[OperationAttributeJobName] = fileName
+	jobAttributes[AttributeJobName] = fileName
 
 	return c.PrintDocuments([]Document{
 		{
@@ -248,13 +248,13 @@ func (c *IPPClient) PrintFile(filePath, printer string, jobAttributes map[string
 
 func (c *IPPClient) GetPrinterAttributes(printer string, attributes []string) (Attributes, error) {
 	req := NewRequest(OperationGetPrinterAttributes, 1)
-	req.OperationAttributes[OperationAttributePrinterURI] = c.getPrinterUri(printer)
-	req.OperationAttributes[OperationAttributeRequestingUserName] = c.username
+	req.OperationAttributes[AttributePrinterURI] = c.getPrinterUri(printer)
+	req.OperationAttributes[AttributeRequestingUserName] = c.username
 
 	if attributes == nil {
-		req.OperationAttributes[OperationAttributeRequestedAttributes] = DefaultPrinterAttributes
+		req.OperationAttributes[AttributeRequestedAttributes] = DefaultPrinterAttributes
 	} else {
-		req.OperationAttributes[OperationAttributeRequestedAttributes] = attributes
+		req.OperationAttributes[AttributeRequestedAttributes] = attributes
 	}
 
 	resp, err := c.SendRequest(c.getHttpUri("printers", printer), req, nil)
@@ -271,7 +271,7 @@ func (c *IPPClient) GetPrinterAttributes(printer string, attributes []string) (A
 
 func (c *IPPClient) ResumePrinter(printer string) error {
 	req := NewRequest(OperationResumePrinter, 1)
-	req.OperationAttributes[OperationAttributePrinterURI] = c.getPrinterUri(printer)
+	req.OperationAttributes[AttributePrinterURI] = c.getPrinterUri(printer)
 
 	_, err := c.SendRequest(c.getHttpUri("admin", ""), req, nil)
 	return err
@@ -279,7 +279,7 @@ func (c *IPPClient) ResumePrinter(printer string) error {
 
 func (c *IPPClient) PausePrinter(printer string) error {
 	req := NewRequest(OperationPausePrinter, 1)
-	req.OperationAttributes[OperationAttributePrinterURI] = c.getPrinterUri(printer)
+	req.OperationAttributes[AttributePrinterURI] = c.getPrinterUri(printer)
 
 	_, err := c.SendRequest(c.getHttpUri("admin", ""), req, nil)
 	return err
@@ -287,12 +287,12 @@ func (c *IPPClient) PausePrinter(printer string) error {
 
 func (c *IPPClient) GetJobAttributes(jobID int, attributes []string) (Attributes, error) {
 	req := NewRequest(OperationGetJobAttributes, 1)
-	req.OperationAttributes[OperationAttributeJobURI] = c.getJobUri(jobID)
+	req.OperationAttributes[AttributeJobURI] = c.getJobUri(jobID)
 
 	if attributes == nil {
-		req.OperationAttributes[OperationAttributeRequestedAttributes] = DefaultJobAttributes
+		req.OperationAttributes[AttributeRequestedAttributes] = DefaultJobAttributes
 	} else {
-		req.OperationAttributes[OperationAttributeRequestedAttributes] = attributes
+		req.OperationAttributes[AttributeRequestedAttributes] = attributes
 	}
 
 	resp, err := c.SendRequest(c.getHttpUri("jobs", jobID), req, nil)
@@ -309,33 +309,33 @@ func (c *IPPClient) GetJobAttributes(jobID int, attributes []string) (Attributes
 
 func (c *IPPClient) GetJobs(printer, class string, whichJobs JobStateFilter, myJobs bool, firstJobId, limit int, attributes []string) (map[int]Attributes, error) {
 	req := NewRequest(OperationGetJobs, 1)
-	req.OperationAttributes[OperationAttributeWhichJobs] = string(whichJobs)
-	req.OperationAttributes[OperationAttributeMyJobs] = myJobs
+	req.OperationAttributes[AttributeWhichJobs] = string(whichJobs)
+	req.OperationAttributes[AttributeMyJobs] = myJobs
 
 	if printer != "" {
-		req.OperationAttributes[OperationAttributePrinterURI] = c.getPrinterUri(printer)
+		req.OperationAttributes[AttributePrinterURI] = c.getPrinterUri(printer)
 	} else if class != "" {
-		req.OperationAttributes[OperationAttributePrinterURI] = c.getClassUri(printer)
+		req.OperationAttributes[AttributePrinterURI] = c.getClassUri(printer)
 	} else {
-		req.OperationAttributes[OperationAttributePrinterURI] = "ipp://localhost/"
+		req.OperationAttributes[AttributePrinterURI] = "ipp://localhost/"
 	}
 
 	if firstJobId > 0 {
-		req.OperationAttributes[OperationAttributeFirstJobID] = firstJobId
+		req.OperationAttributes[AttributeFirstJobID] = firstJobId
 	}
 
 	if limit > 0 {
-		req.OperationAttributes[OperationAttributeLimit] = limit
+		req.OperationAttributes[AttributeLimit] = limit
 	}
 
 	if myJobs {
-		req.OperationAttributes[OperationAttributeRequestingUserName] = c.username
+		req.OperationAttributes[AttributeRequestingUserName] = c.username
 	}
 
 	if attributes == nil {
-		req.OperationAttributes[OperationAttributeRequestedAttributes] = DefaultJobAttributes
+		req.OperationAttributes[AttributeRequestedAttributes] = DefaultJobAttributes
 	} else {
-		req.OperationAttributes[OperationAttributeRequestedAttributes] = append(attributes, OperationAttributeJobID)
+		req.OperationAttributes[AttributeRequestedAttributes] = append(attributes, AttributeJobID)
 	}
 
 	resp, err := c.SendRequest(c.getHttpUri("", nil), req, nil)
@@ -346,7 +346,7 @@ func (c *IPPClient) GetJobs(printer, class string, whichJobs JobStateFilter, myJ
 	jobIDMap := make(map[int]Attributes)
 
 	for _, jobAttributes := range resp.JobAttributes {
-		jobIDMap[jobAttributes[OperationAttributeJobID][0].Value.(int)] = jobAttributes
+		jobIDMap[jobAttributes[AttributeJobID][0].Value.(int)] = jobAttributes
 	}
 
 	return jobIDMap, nil
@@ -354,8 +354,8 @@ func (c *IPPClient) GetJobs(printer, class string, whichJobs JobStateFilter, myJ
 
 func (c *IPPClient) CancelJob(jobID int, purge bool) error {
 	req := NewRequest(OperationCancelJob, 1)
-	req.OperationAttributes[OperationAttributeJobURI] = c.getJobUri(jobID)
-	req.OperationAttributes[OperationAttributePurgeJobs] = purge
+	req.OperationAttributes[AttributeJobURI] = c.getJobUri(jobID)
+	req.OperationAttributes[AttributePurgeJobs] = purge
 
 	_, err := c.SendRequest(c.getHttpUri("jobs", ""), req, nil)
 	return err
@@ -363,8 +363,8 @@ func (c *IPPClient) CancelJob(jobID int, purge bool) error {
 
 func (c *IPPClient) CancelAllJob(printer string, purge bool) error {
 	req := NewRequest(OperationCancelJobs, 1)
-	req.OperationAttributes[OperationAttributePrinterURI] = c.getPrinterUri(printer)
-	req.OperationAttributes[OperationAttributePurgeJobs] = purge
+	req.OperationAttributes[AttributePrinterURI] = c.getPrinterUri(printer)
+	req.OperationAttributes[AttributePurgeJobs] = purge
 
 	_, err := c.SendRequest(c.getHttpUri("admin", ""), req, nil)
 	return err
@@ -372,7 +372,7 @@ func (c *IPPClient) CancelAllJob(printer string, purge bool) error {
 
 func (c *IPPClient) RestartJob(jobID int) error {
 	req := NewRequest(OperationRestartJob, 1)
-	req.OperationAttributes[OperationAttributeJobURI] = c.getJobUri(jobID)
+	req.OperationAttributes[AttributeJobURI] = c.getJobUri(jobID)
 
 	_, err := c.SendRequest(c.getHttpUri("jobs", ""), req, nil)
 	return err
@@ -380,8 +380,8 @@ func (c *IPPClient) RestartJob(jobID int) error {
 
 func (c *IPPClient) HoldJobUntil(jobID int, holdUntil string) error {
 	req := NewRequest(OperationRestartJob, 1)
-	req.OperationAttributes[OperationAttributeJobURI] = c.getJobUri(jobID)
-	req.JobAttributes[PrinterAttributeHoldJobUntil] = holdUntil
+	req.OperationAttributes[AttributeJobURI] = c.getJobUri(jobID)
+	req.JobAttributes[AttributeHoldJobUntil] = holdUntil
 
 	_, err := c.SendRequest(c.getHttpUri("jobs", ""), req, nil)
 	return err
@@ -403,7 +403,7 @@ func (c *IPPClient) PrintTestPage(printer string) (int, error) {
 			MimeType: MimeTypePostscript,
 		},
 	}, printer, map[string]interface{}{
-		OperationAttributeJobName: "Test Page",
+		AttributeJobName: "Test Page",
 	})
 }
 
diff --git a/reqest.go b/reqest.go
index 8223e5b..03a76dc 100644
--- a/reqest.go
+++ b/reqest.go
@@ -59,11 +59,11 @@ func (r *Request) Encode() ([]byte, error) {
 		return nil, err
 	}
 
-	if err := enc.Encode("attributes-charset", Charset); err != nil {
+	if err := enc.Encode(AttributeCharset, Charset); err != nil {
 		return nil, err
 	}
 
-	if err := enc.Encode("attributes-natural-language", CharsetLanguage); err != nil {
+	if err := enc.Encode(AttributeNaturalLanguage, CharsetLanguage); err != nil {
 		return nil, err
 	}
 
diff --git a/response.go b/response.go
index 7ff3e7b..0938761 100644
--- a/response.go
+++ b/response.go
@@ -70,11 +70,11 @@ func (r *Response) Encode(data io.Writer) ([]byte, error) {
 		return nil, err
 	}
 
-	if err := enc.Encode("attributes-charset", Charset); err != nil {
+	if err := enc.Encode(AttributeCharset, Charset); err != nil {
 		return nil, err
 	}
 
-	if err := enc.Encode("attributes-natural-language", CharsetLanguage); err != nil {
+	if err := enc.Encode(AttributeNaturalLanguage, CharsetLanguage); err != nil {
 		return nil, err
 	}