Data and algorithms in APES components are a specific implementation for concepts and algorithms which can be described declaratively (as opposed to imperative description via a programming language) in an ontology. A definition for ontology is that of a shared dictionary. The attributes assigned to concepts, which include for instance relationships of type is-a and has-a, are at the base of the concept of the Semantic Web, and enable effective data search.

APES contains instances of concepts and algorithms implemented via a programming language in discrete software units called components. APES implementation via components separates data and algorithms in discrete software units. Data are defined via types (classes) called Domain Classes, whereas algorithms (i.e. “models”) are implemented via types called Strategies. A component will hence contain one or more domain classes, and typically several strategies; each component has a specific Namespace, which allows to univocally identify all its classes, hence including both Domain Classes and Strategies.

Each of the variables exposed by components is implemented assigning values to a set of attributes, via a type called VarInfo. Attributes are MinimumValue, MaximumValue, DefaultValue, Units, Name, Description and URL. This means that each variable defined in a Domain Class, and each parameter defined in a Strategy, have assigned the attribute values listed above. Such values are used, as an example, for data quality control at run-time, and provide key information to univocally identify a variable. APES interfaces are hence semantically explicit.

The APES Ontology Browser allows accessing information about domain classes and strategy interfaces for each component. The tree-view groups such information at the highest level as domain classes and components, then as namespaces, and finally as types. Types in the group domain classes are actual domain classes used as parameters in the methods of interfaces, whereas types in the group components are strategy classes.

Note that the browser provides visibility on domain classes and strategies as exposed by components, which implies more of what is used in a specific APES instance. In other words, all variables and model interfaces used in APES must be visible in the ontology browser, but what browsable is not necessarily made accessible in APES instances.