Introduction
A 51Degrees on-premise engine adds functionality to an on-premise engine that is specific to 51Degrees. Metadata is exposed which relates to the data structure common to most 51Degrees data files.
In many cases, a 51Degrees engine contains a native binary which the engine acts as a wrapper for. This gives the improved performance achievable with native code, while still seamlessly slotting in with the target language (it is not always obvious that a native binary has been used). It also means that all languages the engine is implemented in can more readily benefit from any optimizations or features which are added to the native library.
See the Specification for more technical details.
Metadata
The majority of 51Degrees engines share a similar data structure. This means metadata is exposed in a common way for all 51Degrees engines that share this structure.
Properties
The properties exposed by a 51Degrees engine should not be seen differently from the element properties or aspect properties that are exposed by any other engine. They merely extend aspect property to add metadata that is specific to the properties in 51Degrees data structures.
The metadata contained in a 51Degrees aspect property is everything in an aspect property with the addition of:
| Metadata | Description |
| Description | A description of the property explaining what it refers to, and what significance its values have. |
| URL | A URL where more information on the property can be found. |
| Component | The component to which the property belongs. This is subtly different from the category, in that a profile defines the values for all the properties of a single component, which likely contains multiple categories of properties. |
| Values | The values that the property can have. As a simple example, a property named 'IsSmartPhone' might have three values: true, false, and unknown. |
| Default Value | The default value for the property if it is not otherwise known. In the above example, the property named 'IsSmartPhone' would probably have unknown as the default value. |
| List | Whether or not the property may have multiple values. For example, the connectivity types a device supports would be a list, as a single device might support Bluetooth, HSDPA, LTE, Wi-Fi, etc. |
| Obsolete | Whether the property is obsolete and only exists to maintain backward compatibility. |
| Display Order | The suggested order in which to display the property when listing properties. |
| Mandatory | Whether the property is mandatory or not. If a property is mandatory, a profile must have a non-default value for it to be classed as valid. |
| Show | Whether the property should be displayed in situations such as a page listing properties. Less important properties may not be displayed. |
| Show Values | Whether values of the property should be displayed in situations such as a page listing the property's values. Showing all the values can make a very long list. |
Values
Values refer to all values which the associated properties can take in the current data file. The metadata for values of a property are exposed by an engine.
Each property has a set of values that it can return. These values are exposed by a 51Degrees engine and give more information on what the implications of a value are.
The metadata contained in a value is:
| Metadata | Description |
| Name | The value as a string. This uniquely identifies the value only within the values relating to the same property. |
| Property | The property to which the value relates. This, in combination with the name, uniquely identifies the value within the 51Degrees engine it belongs to. For example, there may be many values whose name is true, but each is a value for a different property. |
| Description | A description of the value explaining what it refers to, and what it means if a profile has this value. |
| URL | A URL where more information on the value can be found. |
Components
A component defines a group of properties that are related.
In a 51Degrees data set, a property only exists in a single component. For example, the Browser Name property is part of the Software component, whereas the Model Name property is part of the Hardware component.
The metadata contained in a component is:
| Metadata | Description |
| Id | The unique id of the component. This is usually a number and will remain the same when a data file is updated. |
| Name | The name of the component that gives a more 'human' identifier than id. By convention, this is unique within the data file. |
| Default profile | The default profile for the component. This is used to provide values for the component's properties when a profile matching the evidence cannot be found. |
| Properties | The properties associated with this component. |
Profiles
A profile defines a unique set of values for all properties of a single component.
An engine will populate aspect data with at least one profile for each component in the data file. This means that all properties should be able to present a value, even if that value is 'Unknown'.
Internally, this is how values are stored in element data once evidence has been processed. However, these profiles are also exposed directly as metadata so all possible results can be interrogated. The metadata contained in a profile is:
| Metadata | Description |
| Id | The unique id of the profile. This is usually a number and will remain the same when a data file is updated. |
| Name | The name of the profile that gives a more 'human' identifier than id, usually describing what the values it contains are. By convention, this is unique within the data file. |
| Component | The component to which the profile relates. This is the component which the profile contains values for. |
| Values | The values that define the profile. |
| Signature Count | The number of signatures that define how to find the profile. This is internal to the engine and differs slightly in meaning between each. |
Native library
Most 51Degrees on-premise engines act as a wrapper between the target language and a native library.
When the engine is packaged for release to a target language's package manager, multiple native binaries are included. Each is compiled for a specific platform (e.g., 32-bit Windows, or 64-bit OS X) and the correct binary is automatically selected at start-up.