## Catalogs in DocDigitizer WorldObjects
**DocDigitizer WorldObjects** you can choose what information you want to work with, then let the system retrieve the data from the appropriate systems without you knowing what the source systems are.
**DocDigitizer WorldObjects** provide functionalities where you can associate the "data domain" related to each object, this is, associate list of values like "list of countries", which we refer as Catalogs
This Catalogs can be "managed":
**Local Catalogs** managed "client-side", where the data can be stored in “in code" (DLL Resource).
**Remote Catalogs** managed "server-side", access by an API, where the data can be store in Database or "DLL Resource". Example of "Local Catalog"&“in code"
You can also use Catalogs (and is related semantic objects) shipped by with **DocDigitizer WorldObjects**.
## Validators in DocDigitizer WorldObjects
**Validators** give the ability to create and define syntactic and semantic validation rules
This means the ability to validate if an identifier is valid. For instance, ability to validate if **fiscal number** is valid in a certain country, our **zip code**. The validator takes into account which country the **zip code** relates to. With this we save developers from coding by themselves the validation of **zip code** and maintenance of the information (Catalog) from all countries.
You can use Validators for instance to check mandatory properties (fields):
The **DocDigitizer** offer some Validators but you can extend them, creating your own **Validators**.
## Formatters in DocDigitizer WorldObjects
**Formatters** give the ability to create and define typical patterns of data transformations.
For instance formatting the values **IBAN** to be return by an API or the will be show webpage.
Like the previous cases mentions, **DocDigitizer** offer some **Formatters** but you can extend them, creating your own **Formatters**.
## Expressions in DocDigitizer WorldObjects
**Expressions** is more generic that the two previous features (Validators & Formatters) and give more flexibility how to use them and the objectives.
For instance returning last name (surname) of the full name.