I was researching about "sanitize" data and found this answer from @maniero , which cites:
"Delete text snippets in a data entry that have characteristics of metadata , and therefore may cause some security issue. "
I would like to understand what would be metadata and what application / utility would they have?
Meta, from the Greek (μετά), means "behind" or "beyond." Metadata is information about a given.
Think of a photo taken from a camera:
Thedataitselfistheimage.It'swhatyouseeabove.Themetadatacouldbe:
Theyareinformationaboutthedata.Itisthegoal,thebehindandthebeyondoftheimageitself.
Itisclearthatthisisnotatermofthetechnologyarea,butapplicabletoanytypeofdata,object,photograph,softwareorthingyoucanimagine.Thisisatermthat#
To contextualize information technology, let's look at the metadata of a file:
Every file in the operating system has metadata. This is saved to disk and takes up space. So a 1 kb file is actually 1 kb + size of your metadata.
One of the specifications for building Web APIs is the JSON API . Following this specification, suppose you have a paged product listing API:
GET /api/produtos
{
"produtos": [ ... ],
"meta": {
"paginaAtual": 1,
"proximaPagina": "api/produtos?pagina=2",
"paginaAnterior": null
}
}
See that there is a meta node that has no connection to a product, which is what this endpoint provides. It is about pagination. It is information beyond and above the die.
On the internet pages the scheme is no different. A page like your Facebook profile should contain your timeline, your name, your photo and the like. In addition to all this data, there are some more dedicated to metadata.
That's what the meta HTML tag is for. It was made to be read by machines and not by an end user. They are information about the page.
<head>
<meta charset="UTF-8">
<meta name="description" content="Free Web tutorials">
<meta name="keywords" content="HTML,CSS,XML,JavaScript">
<meta name="author" content="John Doe">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
</head>
Here, in this W3C example, page metadata would be a description, keywords, page author, and so on.
Relational database DBMSs also have metadata. A person table can contain entities with name, date of birth and CPF. Content is entities. But if I ask the question "what are the columns of the people table?", This is a question about the metadata of this table.
Some metadata examples from a database table:
This data, in fact, is stored somewhere. In SQL Server you can view them in the sys.columns table. An example:
SELECT name, column_id
FROM sys.columns
WHERE object_id = OBJECT_ID(N'Pessoa.Cpf');
If you want to read more about, see Querying the SQL Server Catalog .
Metaprogramming addresses this part in languages. Maniero replied with a my question about the difference between metaprogramming and reflection , which is worth reading. There he defined the metaprogramming briefly:
A paradigm that allows the manipulation of the More generally, you program how the code should be programmed.
An example of a code reading to yourself in Ruby:
class Developer
def self.backend
"I am backend developer"
end
def frontend
"I am frontend developer"
end
end
p Developer.class => Class
p Class.superclass => Module
p Module.superclass => Object
p Object.superclass => BasicObject
An interesting example is the .bmp (bitmap image file) format of images. If you observe the contents of this file raw, you will see that it follows the following pattern:
You can see that much of this information is not the matrix of the image itself, but rather the metadata of that image. As you mentioned, there is no problem in sanitizing some of this information in many cases.
