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Los mitos sobre las criptomonedas (y en especial, Bitcoin)

Recientemente tuve una pequeña discusión en LinkedIn con el señor Antonio T. Miranda Oliván sobre la consideración de Bitcoin (y las criptomonedas) como burbuja, ya que este señor participó en una página web en la que publicó un artículo crítico con la útlima burbuja.

Me dije a mí mismo que escribiría una respuesta razonada sobre el tema, argumentando porqué el artículo es todo un despropósito basado el falacias.
Para empezar, quiero indicar dos cosas. La primera es que hablamos de Bitcoin y del resto de criptomonedas, porque BTC actúa como cabeza de una familia, así que este artículo no va de Bitcoin en particular, si no que se extendie a todas las criptomonedas. Junto a esto, decir, que Bitcoin me parece una de las criptomonedas famosas más inútiles a día de hoy. La segunda cosa, es que desde aquí animo encarecidamente al autor a que, cuando haga afirmaciones tan tajantes e importantes (luego discutiremos cuáles son), se moleste al menos en indicar las fuentes y datos donde las resp…

¿Es aceptable la discriminación a la hora de contratar?


Recientemente estaba haciendo una práctica de Análisis de datos en la que, como entrevistadores de futuros becarios en una gran firma, teníamos que determinar que tipos de perfiles se quedaban en la compañía pasado el período de prácticas y cuáles no.
Esto lo quería realizar la compañía pues le interesaba que los becarios se quedaran en la compañía después de las prácticas, ya que la formación les suponía un enrome coste.

El caso es que nunca me había planteado esto, siempre oímos que no se puede o no se debería de poder discriminar a la hora de seleccionar personal, y entiendo que en una entrevista nadie, repito, nadie, debería preguntarte si estás casado, tienes hipoteca o te vas a quedar embarazada.

Pero, ¿por qué no discriminar sin que los candidatos lo sepan? Es decir, antes de las entrevistas, como preselección. Obviamente, supongo que, para bien o para mal, ya sea hace a escondidas; pero mi planteamiento lo intenta ver desde la óptica del razonamiento objetivo.

University teaching systems: USA vs Spain

One sentence: Quality VS Quantity.

I'm so shocked, I'm taking an upper-level (47...) class called Quantitative Economic Analysis, which sounds pretty hard and mathematical.
The thing is that, although our teacher is one of the best teachers ever (he is funny and his explanations are soooo clear), the contents of the course fall under what I learnt in High School.

I'll show you an example. In my first year of college I had two mandatory courses, called Math I and Math II, which included: matrices, derivatives, integrals, optimization, multivariate optimization, constraint optimization, Simplex method and series and sequences.
And they taught that in an fast way, like "hey, you already learnt derivatives in High School (it is mandatory to study for any kind of economics/business degree), so let's take only one hour to review some key concepts and then skip it".

And after those courses, whenever we had to use some of the concepts learnt at that time, our teache…

What are Candidate, Primary and Foreign Keys?

CK (Candidate Key). These are the Keys that may be defined as Primary keys, and must enforce these properties.Properties:Uniqueness. It must have a unique value, that is we cannot have at any given time the same value for the attribute at more than one tuple. Example: we cannot have the same SSN for two or more individuals, or a person can't have more than one SSN.Minimality. If it is a composite attribute (as an address), no component of the attribute can be deleted without destroying the uniqueness property.PK (Foreign Key). The most representative CK or CKs (we can have a composite PK) of the Entity Set are selected to use them to identify each Entity of an Entity Set. Example: The Entity Set "Student" has "Student Identification Number" as a PK.FK (Foreign Key). What if we have a table with Students which include, for each student, the "Identification Number" of each student's advisor (that is the PK of "Student advisor" in "Stu…

Integrity constraints for relational databases

When we want to create a relational database, we must comply with four integrity constraints in order for our DB to work correctly.

Entity integrity constraint. A PK (Primary Key) cannot allow null valuesEnforcement: check for null values when enter data.Key integrity constraint. No two tuples can have the same attribute value.Enforcement: check duplicity.Referential integrity constraint. We cannot have any unmatched FK (Foreign Key). That is, if B references A, A must exist.Enforcement:Restriction. The Update/delete of PK is restricted to not having a matching FK.Nullification. Update/delete of PK can only be done after setting any FK to null.Cascading. Update/delete of PK cascades to any FK.Semantic integrity constraint. We must use data that makes sense. We look for semantic correctness.Enforcement: use restrictions when enter data such as: length, legal values (i.e. car brands), types of data (i.e. currency, date, etc.), range, etc.

Steps in Database design and implementation

What are the main and necessary steps in the DB design and implementation process?
Let's enumerate and explain them...

User requirements. First we need them, we need a user capable of using a computer, understanding our language, etc.Conceptual design. This is used to describe information that the DB will contain. This is where we typically use the ER (Entity - Relationship) model, although some people refer to this design as drawing a simple schema about relationships without using the full version of ER model.  Input: Requirement specifications to build the DBOutput: Conceptual schemaLogical design. Used to describe the structure of the DB that can be processed by the DBMS (Database Management System), it can depend on the type of data the DBMS can used but not on the DBMS itself. Here we'll use the ER, including Attributes and Primary, Foreign an Alternative keys.Input: Conceptual schemaOutput: Logical schema Physical design. At this point we create the file index and the de…

Components of a Database environment

Users. Obviously, why would we want a DB if we don't have users?DBMS (Database Management System, such Microsoft Access). That includesDDL (Data Definition Language). Which creates and modifies the logical structure of the DB (objects).DML (Data Manipulation Language). It's used to manipulate and process data (retrieve, update, add) of the DB. I.e.: SQL.DBA (Database Administrator). It has two main functions:Plans, designs, implements and do maintenance and protection functions for the DBDefines data dictionary, which means that defines the meaning of data and describes interrelations between data items.DB itself. Finally we have the Database, which has its physical format and it's a collection of data.

Main functions of Databases

What are the main functions of a DB (Database) ?

Data definition. A DB should allow us to accept data definitions as those provided by the different types of schemas we had made to build our DB. This also includes a language processor component for each of the DDL (Data Definition Language: used to create and modifiy the logical structure (objects) of the DB)Data manipulation. Users will retrieve information, as well as update and add new information. This includes a processor for DML (Data Manipulation Language: which allows the user to do such actions (retrieve, update, add); SQL is a DML).Data security and integrity. Must have some mechanisms to control users requests and enforce the rules (security & integrity) defined by the DBA (Database Administrator).Data recovery and concurrency. What's concurrency? That's data at the same time, okay, never though of what happens when two users are editing at the same time the same tuple? That's a concurrency problem. Also, DB …

File-oriented approach VS Database approach

One of the first lectures of my Database design class was the explanation of the differences between the file-oriented approach and the database approach when dealing with the storage and manipulation of data.

In a nutshell, we can say distinguish between the following advantages VS disadvantages.
But first, what is file-oriented approach? That's an "old" system where files are stored separately and each one of them is independent from the others. On the other side, a database approach allows us to associate data and keep and interdependent system.

File-oriented approach disadvantagesData redundancy. There will be duplicates, as the files are created independently.This increases maintenance costsAnd also leads to data inconsistency, due to duplicates and/or similar data stored in different formats.Lack of data integration. This means we cannot associate data, as there are no association mechanisms.Program/data dependence to the physical format (the files themselves)Lack …

How to solve Firebase "failed to resolve"

I spent 5 days trying to solve this simple error. If you try to add Firebase to your project through Android Studio Firebase menu, you may have this problem.

DESCRIPTION: Firebase is connected and so firebase:firebase-core:XX.X.X works, but then you wanto add a realtime database or the authentication package and the you find the next error:

Failed to resolve: firebase-database-15.0.0

I don't know why Firebase adds old versions to your project instead of the latest stable version, but here's the solution.

Just change your

implementation ''implementation ''implementation ''
to the last version of each Firebase package (here) which, at the moment of writing this post, were the following:

implementation ''implementation ''implementation …

Firebase Auth error login

I'm studying a Android-Java developer course, and we are designing an application that uses Email and Password login.

So when we enter the correct email and password a Toast will show up saying "Successful sign in!", the opposite will be "Failed to sign in!".

The problem was that I was always getting a "Failed to sign in!" and I knew my email and password were correct. I didn't get any error in the Logcat, only some weird line from getGoogleApiForMethod.

So I just came up with this marvelous idea: "Just add an exception log to your f*** code!"
And so I did. I added a

Log.e(TAG, "Failed because of: " + task.getException().getMessage());
after my

And then I discovered the following:

An internal error has occurred. [ Identity Toolkit API has not been used in project BLAHBLAH before or it is disabled. Enable it by visiting…