1 <!-- 2 Copyright 2010 The Android Open Source Project 3 4 Licensed under the Apache License, Version 2.0 (the "License"); 5 you may not use this file except in compliance with the License. 6 You may obtain a copy of the License at 7 8 http://www.apache.org/licenses/LICENSE-2.0 9 10 Unless required by applicable law or agreed to in writing, software 11 distributed under the License is distributed on an "AS IS" BASIS, 12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 See the License for the specific language governing permissions and 14 limitations under the License. 15 --> 16 17 # Compatibility Program Overview # 18 19 The Android compatibility program makes it easy for mobile device 20 manufacturers to develop compatible Android devices. 21 22 # Program goals # 23 24 The Android compatibility program works for the benefit of the entire 25 Android community, including users, developers, and device manufacturers. 26 27 Each group depends on the others. Users want a wide selection of devices 28 and great apps; great apps come from developers motivated by a large market 29 for their apps with many devices in users' hands; device manufacturers rely 30 on a wide variety of great apps to increase their products' value for 31 consumers. 32 33 Our goals were designed to benefit each of these groups: 34 35 - *Provide a consistent application and hardware environment to application 36 developers.* 37 Without a strong compatibility standard, devices can vary so 38 greatly that developers must design different versions of their applications 39 for different devices. The compatibility program provides a precise definition 40 of what developers can expect from a compatible device in terms of APIs and 41 capabilities. Developers can use this information to make good design 42 decisions, and be confident that their apps will run well on any compatible 43 device. 44 45 - *Enable a consistent application experience for consumers.* 46 If an application runs well on one compatible Android device, it should run well on 47 any other device that is compatible with the same Android platform version. 48 Android devices will differ in hardware and software capabilities, so the 49 compatibility program also provides the tools needed for distribution systems 50 such as Android Market to implement appropriate filtering. This means that 51 users can only see applications which they can actually run. 52 53 - *Enable device manufacturers to differentiate while being 54 compatible.* 55 The Android compatibility program focuses on the aspects of 56 Android relevant to running third-party applications, which allows device 57 manufacturers the flexibility to create unique devices that are nonetheless 58 compatible. 59 60 - *Minimize costs and overhead associated with compatibility.* 61 Ensuring compatibility should be easy and inexpensive to 62 device manufacturers. The testing tool (CTS) is free, open source, and 63 available for [download](downloads.html). 64 CTS is designed to be used for continuous self-testing 65 during the device development process to eliminate the cost of changing your 66 workflow or sending your device to a third party for testing. Meanwhile, there 67 are no required certifications, and thus no corresponding costs and 68 fees. 69 70 The Android compatibility program consists of three key components: 71 72 - The source code to the Android software stack 73 - The Compatilbility Definition Document, representing the "policy" aspect of compatibility 74 - The Compatilbility Test Suite, representing the "mechanism" of compatibility 75 76 Just as each version of the Android platform exists in a separate branch in 77 the source code tree, there is a separate CTS and CDD for each version as 78 well. The CDD, CTS, and source code are -- along with your hardware and your 79 software customizations -- everything you need to create a compatible device. 80 81 # Compatibility Definition Document (CDD) # 82 83 For each release of the Android platform, a detailed Compatibility 84 Definition Document (CDD) will be provided. The CDD represents the "policy" 85 aspect of Android compatibility. 86 87 No test suite, including CTS, can truly be comprehensive. For instance, the 88 CTS includes a test that checks for the presence and correct behavior of 89 OpenGL graphics APIs, but no software test can verify that the graphics 90 actually appear correctly on the screen. More generally, it's impossible to 91 test the presence of hardware features such as keyboards, display density, 92 WiFi, and Bluetooth. 93 94 The CDD's role is to codify and clarify specific requirements, and 95 eliminate ambiguity. The CDD does not attempt to be comprehensive. Since 96 Android is a single corpus of open-source code, the code itself is the 97 comprehensive "specification" of the platform and its APIs. The CDD acts as a 98 "hub", referencing other content (such as SDK API documentation) that provides 99 a framework in which the Android source code may be used so that the end 100 result is a compatible system. 101 102 If you want to build a device compatible with a given Android version, 103 start by checking out the source code for that version, and then read the 104 corresponding CDD and stay within its guidelines. For additional details, 105 simply examine [the latest CDD](2.3/android-2.3.3-cdd.pdf). 106 107 # Compatibility Test Suite (CTS) # 108 109 The CTS is a free, commercial-grade test suite, available for 110 [download](downloads.html). 111 The CTS represents the "mechanism" of compatibility. 112 113 The CTS runs on a desktop machine and executes test cases directly on 114 attached devices or an emulator. The CTS is a set of unit tests designed to be 115 integrated into the daily workflow (such as via a continuous build system) of 116 the engineers building a device. Its intent is to reveal incompatibilities 117 early on, and ensure that the software remains compatible throughout the 118 development process. 119 120 121 # Compatibility Test Suite Verifier (CTS Verifier) # 122 The Compatibility Test Suite Verifier (CTS Verifier) is a supplement to the 123 Compatibility Test Suite (CTS), available for [download](downloads.html). 124 CTS Verifier provides tests for APIs and functions that cannot be tested on a 125 stationary device without manual input (e.g. audio quality, accelerometer, etc). 126 127 For details on the CTS, consult the [CTS introduction](cts-intro.html). 128
