In order to provide consistent developer experience across many APIs and over a long period of time, all names used by an API shouldbe:
- simple
- intuitive
- consistent
This includes names of interfaces, resources, collections, methods, and messages.
Since many developers are not native English speakers, one goal of these naming conventions is to ensure that the majority of developers can easily understand an API. It does this by encouraging the use of a simple, consistent, and small vocabulary when naming methods and resources.
- Names used in APIs shouldbe in correct American English. For example, license (instead of licence), color (instead of colour).
- Commonly accepted short forms or abbreviations of long words maybe used for brevity. For example, API is preferred over Application Programming Interface.
- Use intuitive, familiar terminology where possible. For example, when describing removing (and destroying) a resource, delete is preferred over erase.
- Use the same name or term for the same concept, including for concepts shared across APIs.
- Avoid name overloading. Use different names for different concepts.
- Avoid overly general names that are ambiguous within the context of the API and the larger ecosystem of Google APIs. They can lead to misunderstanding of API concepts. Rather, choose specific names that accurately describe the API concept. This is particularly important for names that define first-order API elements, such as resources. There is no definitive list of names to avoid, as every name must be evaluated in the context of other names. Instance, info, and service are examples of names that have been problematic in the past. Names chosen should describe the API concept clearly (for example: instance of what?) and distinguish it from other relevant concepts (for example: does "alert" mean the rule, the signal, or the notification?).
- Carefully consider use of names that may conflict with keywords in common programming languages. Such names maybe used but will likely trigger additional scrutiny during API review. Use them judiciously and sparingly.
Product names
Product names refer to the product marketing names of APIs, such as Google Calendar API . Product names mustbe consistently used by APIs, UIs, documentation, Terms of Service, billing statements, commercial contracts, etc. Google APIs mustuse product names approved by the product and marketing teams.
The table below shows examples of all related API names and their consistency. See further below on this page for more details on the respective names and their conventions.
API Name | Example |
---|---|
Product Name | Google Calendar API
|
Service Name | calendar.googleapis.com
|
Package Name | google.calendar.v3
|
Interface Name | google.calendar.v3.CalendarService
|
Source Directory | //google/calendar/v3
|
API Name | calendar
|
Service names
Service names shouldbe syntactically valid DNS names (as per RFC
1035
) which can be resolved to one
or more network addresses. The service names of public Google APIs
follow the pattern: xxx.googleapis.com
. For example, the service name
of the Google Calendar is calendar.googleapis.com
.
If an API is composed of several services they shouldbe named in
a way to help discoverability. One way to do this is for the Service Names
to share a common prefix. For example the services build.googleapis.com
and buildresults.googleapis.com
are both services that are part of the Google
Build API.
Package names
Package names declared in the API .proto files shouldbe consistent with Product Names and Service Names. Package names shoulduse singular component names to avoid mixed singular and plural component names. Package names must notuse underscores. Package names for versioned APIs mustend with the version. For example:
// Google Calendar API
package
google
.
calendar.v3
;
An abstract API that isn't directly associated with a service, such as Google Watcher API, shoulduse proto package names consistent with the Product name:
// Google Watcher API
package
google
.
watcher.v1
;
Java package names specified in the API .proto files mustmatch the
proto package names with standard Java package name prefix ( com.
, edu.
, net.
, etc). For example:
package
google
.
calendar.v3
;
// Specifies Java package name, using the standard prefix "com.
" option
java_package
=
" com.google.calendar.v3
" ;
Collection IDs
Collection IDs
shoulduse
plural form and lowerCamelCase
, and American English spelling and
semantics. For example: events
, children
, or deletedEvents
.
Interface names
To avoid confusion with Service Names
such as pubsub.googleapis.com
, the term interface name
refers to the name
used when defining a service
in a .proto file:
// Library is the interface name.
service
Library
{
rpc
ListBooks
(
...
)
returns
(
...
);
rpc
...
}
You can think of the service name as a reference to the actual implementation of a set of APIs, while the interface name refers to the abstract definition of an API.
An interface name shoulduse an intuitive noun such as Calendar or Blob. The name should notconflict with any well-established concepts in programming languages and their runtime libraries (for example, File).
In the rare case where an interface name
would conflict with another
name within the API, a suffix (for example Api
or Service
) shouldbe used to disambiguate.
Method names
A service may, in its IDL specification, define one or more RPC
methods that correspond to methods on collections and resources. The
method names shouldfollow the naming convention of VerbNoun
in
upper camel case, where the noun is typically the resource type.
Verb | Noun | Method name | Request message | Response message |
---|---|---|---|---|
List
|
Book
|
ListBooks
|
ListBooksRequest
|
ListBooksResponse
|
Get
|
Book
|
GetBook
|
GetBookRequest
|
Book
|
Create
|
Book
|
CreateBook
|
CreateBookRequest
|
Book
|
Update
|
Book
|
UpdateBook
|
UpdateBookRequest
|
Book
|
Rename
|
Book
|
RenameBook
|
RenameBookRequest
|
RenameBookResponse
|
Delete
|
Book
|
DeleteBook
|
DeleteBookRequest
|
google.protobuf.Empty
|
The verb portion of the method name shoulduse the imperative mood , which is for orders or commands rather than the indicative mood which is for questions.
For standard methods, the noun portion of the method name mustbe singular
for all methods except List
, and mustbe plural for List
. For custom
methods, the noun maybe singular or plural as appropriate. Batch methods mustuse the plural noun.
This is easily confused when the verb is asking a question about a sub-resource
in the API, which is often expressed in the indicative mood. For example,
ordering the API to create a book is clearly CreateBook
(in the imperative
mood), but asking the API about the state of the book's publisher might use the
indicative mood, such as IsBookPublisherApproved
or NeedsPublisherApproval
.
To remain in the imperative mood in situations like this, rely on commands such
as "check" ( CheckBookPublisherApproved
) and "validate"
( ValidateBookPublisher
).
Method names should notinclude prepositions (e.g. "For", "With", "At", "To"). Generally, method names with prepositions indicate that a new method is being used where a field should instead be added to an existing method, or the method should use a distinct verb.
For example, if a CreateBook
message already exists and you are considering
adding CreateBookFromDictation
, consider a TranscribeBook
method
instead.
Message names
Message names shouldbe short and concise. Avoid unnecessary or redundant
words. Adjectives can often be omitted if there is no corresponding message
without the adjective. For example, the Shared
in SharedProxySettings
is
unnecessary if there are no unshared
proxy settings.
Message names should notinclude prepositions (e.g. "With", "For"). Generally, message names with prepositions are better represented with optional fields on the message.
Request and response messages
The request and response messages for RPC methods shouldbe named
after the method names with the suffix Request
and Response
,
respectively, unless the method request or response type is:
- an empty message (use
google.protobuf.Empty
), - a resource type, or
- a resource representing an operation
This typically applies to requests or responses used in standard methods Get
, Create
, Update
, or Delete
.
Enum names
Enum types mustuse UpperCamelCase names.
Enum values mustuse CAPITALIZED_NAMES_WITH_UNDERSCORES. Each enum value mustend with a semicolon, not a comma. The first value shouldbe named ENUM_TYPE_UNSPECIFIED as it is returned when an enum value is not explicitly specified.
enum
FooBar
{
// The first value represents the default and must be == 0.
FOO_BAR_UNSPECIFIED
=
0
;
FIRST_VALUE
=
1
;
SECOND_VALUE
=
2
;
}
Wrappers
Messages encapsulating proto2 enum types where the 0
value has meaning other
than UNSPECIFIED
shouldbe named with the suffix Value
and have a single
field named value
.
enum
OldEnum
{
VALID
=
0
;
OTHER_VALID
=
1
;
}
message
OldEnumValue
{
OldEnum
value
=
1
;
}
Field names
Field definitions in the .proto files mustuse lower_case_underscore_separated_names. These names will be mapped to the native naming convention in generated code for each programming language.
Field names should notinclude prepositions (e.g. "for", "during", "at"), for example:
-
reason_for_error
should instead beerror_reason
-
cpu_usage_at_time_of_failure
should instead befailure_time_cpu_usage
Field names should notuse postpositive adjectives (modifiers placed after the noun), for example:
-
items_collected
should instead becollected_items
-
objects_imported
should instead beimported_objects
Repeated field names
Repeated fields in APIs mustuse proper plural forms. This matches the convention of existing Google APIs, and the common expectation of external developers.
Time and Duration
To represent a point in time independent of any time zone or calendar, google.protobuf.Timestamp
shouldbe used, and the field name shouldend with time
, such as start_time
and end_time
.
If the time refers to an activity, the field name shouldhave the
form of verb_time
, such as create_time
, update_time
. Avoid using
past tense for the verb, such as created_time
or last_updated_time
.
To represent a span of time between two points in time independent of
any calendar and concepts like "day" or "month", google.protobuf.Duration
shouldbe used.
message
FlightRecord
{
google.protobuf.Timestamp
takeoff_time
=
1
;
google.protobuf.Duration
flight_duration
=
2
;
}
If you have to represent time-related fields using an integer type for legacy or compatibility reasons, including wall-clock time, duration, delay and latency, the field names musthave the following form:
xxx_{time|duration|delay|latency}_{seconds|millis|micros|nanos}
message
Email
{
int64
send_time_millis
=
1
;
int64
receive_time_millis
=
2
;
}
If you have to represent timestamp using string type for legacy or compatibility reasons, the field names should notinclude any unit suffix. The string representation shoulduse RFC 3339 format, e.g. "2014-07-30T10:43:17Z".
Date and Time of Day
For dates that are independent of time zone and time of day, google.type.Date
shouldbe used and it should have the suffix _date
. If a date must be
represented as a string, it should be in the ISO 8601 date format YYYY-MM-DD,
e.g. 2014-07-30.
For times of day that are independent of time zone and date, google.type.TimeOfDay
shouldbe used and should have the suffix _time
. If a time of day must be
represented as a string, it should be in the ISO 8601 24-hour time format
HH:MM:SS[.FFF], e.g. 14:55:01.672.
message
StoreOpening
{
google.type.Date
opening_date
=
1
;
google.type.TimeOfDay
opening_time
=
2
;
}
Quantities
Quantities represented by an integer type mustinclude the unit of measurement.
xxx_{bytes|width_pixels|meters}
If the quantity is a number of items, then the field shouldhave the suffix _count
, for example node_count
.
List filter field
If an API supports filtering of resources returned by the List
method,
the field containing the filter expression shouldbe named filter
.
For example:
message
ListBooksRequest
{
// The parent resource name.
string
parent
=
1
;
// The filter expression.
string
filter
=
2
;
}
List response
The name of the field in the List
method's response message, which
contains the list of resources mustbe a plural form of the resource
name itself. For example, a method CalendarApi.ListEvents()
mustdefine a response message ListEventsResponse
with a repeated field
called events
for the list of returned resources.
service
CalendarApi
{
rpc
ListEvents
(
ListEventsRequest
)
returns
(
ListEventsResponse
)
{
option
(
google.api.http
)
=
{
get
:
" /
v3
/
{
parent
=
calendars
/
*
}
/
events
" ;
};
}
}
message
ListEventsRequest
{
string
parent
=
1
;
int32
page_size
=
2
;
string
page_token
=
3
;
}
message
ListEventsResponse
{
repeated
Event
events
=
1
;
string
next_page_token
=
2
;
}
Camel case
Except for field names and enum values, all definitions inside .proto
files mustuse UpperCamelCase names, as defined by Google Java
Style
.
Name abbreviation
For well known name abbreviations among software developers, such as config
and spec
, the abbreviations shouldbe used in API definitions instead
of the full spelling. This will make the source code easy to read and write.
In formal documentations, the full spelling shouldbe used. Examples:
- config (configuration)
- id (identifier)
- spec (specification)
- stats (statistics)