Serializers and deserializers for the data access layer of Wikibase Repository

2.10.0 2020-01-24 12:24 UTC


Library containing serializers and deserializers for the data access layer of Wikibase Repository.

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The recommended way to use this library is via Composer.


To add this package as a local, per-project dependency to your project, simply add a dependency on wikibase/internal-serialization to your project's composer.json file. Here is a minimal example of a composer.json file that just defines a dependency on version 2.x of this package:

    "require": {
        "wikibase/internal-serialization": "~2.0"


Get the code of this package, either via git, or some other means. Also get all dependencies. You can find a list of the dependencies in the "require" section of the composer.json file. Then take care of autoloading the classes defined in the src directory.

Library usage

Construct an instance of the deserializer or serializer you need via the appropriate factory.

use Wikibase\InternalSerialization\DeserializerFactory;

$deserializerFactory = new DeserializerFactory( /* ... */ );
$entityDeserializer = $deserializerFactory->newEntityDeserializer();

The use the deserialize or serialize method.

$entity = $entityDeserializer->deserialize( $myEntitySerialization );

In case of deserialization, guarding against failures is good practice. So it is typically better to use the slightly more verbose try-catch approach.

try {
	$entity = $entityDeserializer->deserialize( $myEntitySerialization );
catch ( DeserializationException $ex ) {
	// Handling of the exception

All access to services provided by this library should happen through the SerializerFactory and DeserializerFactory. The rest of the code is an implementation detail which users are not allowed to know about.

Library structure

The Wikibase DataModel objects can all be serialized to a generic format from which the objects can later be reconstructed. This is done via a set of Serializers\Serializer implementing objects. These objects turn for instance a Claim object into a data structure containing only primitive types and arrays. This data structure can thus be readily fed to json_encode, serialize, or the like. The process of reconstructing the objects from such a serialization is provided by objects implementing the Deserializers\Deserializer interface.

Serializers can be obtained via an instance of SerializerFactory and deserializers can be obtained via an instance of DeserializerFactory. You are not allowed to construct these serializers and deserializers directly yourself or to have any kind of knowledge of them (ie type hinting). These objects are internal to this serialization and might change name or structure at any time. All you are allowed to know when calling $serializerFactory->newEntitySerializer() is that you get back an instance of Serializers\Serializer.

The library contains deserializers that handle the legacy internal serialization format. Those can be found in Wikibase\InternalSerialization\Deserializers, and all start with the word "Legacy". The remaining deserializers in this namespace are not specific to any format. They detect the one that is used and forward to the appropriate deserializer. These deserializers can thus deal with serializations in the old legacy format and those in the new one.

The DeserializerFactory only returns deserializers that can deal with both the legacy and the new format.


This library comes with a set up PHPUnit tests that cover all non-trivial code. You can run these tests using the PHPUnit configuration file found in the root directory. The tests can also be run via TravisCI, as a TravisCI configuration file is also provided in the root directory.


Wikibase Internal Serialization has been written by Jeroen De Dauw, partially as Wikimedia Germany employee for the Wikidata project.


See also