A music group called inerKor
Once upon a long ago, two friends of mine (Fernando aka tibu and Javi aka mono) started playing the guitar. They decided to form a group. Soon after I joined them as drum player. Inerkor was born. We tried to include a bassist but after many trials it was not possible. One of our best friends -- Alfonso -- played for a while but unfortunately he left it. So eventually inerkor was a group of three, without bass (who needs it with a double bass drum?).
Our style was influenced by groups like Pantera, Metallica, Napalm Death and many others. Truth is that we spent a lot of time listening to other groups and going to concerts. So you can imagine that our music was pretty noisy, but we introduced certain melodic parts (even with those broken guitars and the double bass drum going full pelt). Really cool.
Our lyrics would have been under a parental advisory label. No doubt. Titles like "suicide time" or "I'd enjoy killing you, motherfucker" say it all. The message was pretty pessimistic, but in line with our feelings and the facts of society we were facing. Even though we really enjoyed, I think anger prevailed in our concerts, music and lyrics. I am not sure anger against what. Looking back I realize that this anger has not faded away, not as that friendship that seems to last forever.
We played for over seven years, giving concerts here and there (one of my dearest memories is our concert in Firenze, Italy), recorded one demo that unfortunately I do not keep (otherwise you could download it from this webpage, be sure) and quit in our best moment I think. I mean that we were good enough to play almost any group and our music was not bad (well, I could not say any other thing).
A few weeks ago, surfing the web, by chance (by a mistake: I introduced the name of the group in the google bar instead of in my gmail account) I discovered a video in which the lead guitar, tibu, was playing kind of celtic music in a collaboration with other people. I have not seen him for over eight years and it was very, very moving. The video is this one.
Many, many things changed in my life at the age of 27/28. Another day, another post, I will tell you about other deep changes. It seems that I got sentimental. Okay, we will return to maths and MGG in the next post. Reading again this post, it does not do Inerkor or my friends justice, so this quote from Gustave Flaubert seems appropriate: writing history is like drinking an ocean and pissing a cupful.
lunes, 26 de marzo de 2012
miércoles, 14 de marzo de 2012
derivations III
derivations and direct derivations. Part III (epsilon-productions)
Today I touch on dangling edges. Let p be a production that specifies the deletion of one node (the LHS -- left hand side -- is made up of a single node and its RHS is empty). Suppose the production is applied to a graph with no isolated nodes. What happens with the edges that are incident to the node that p deletes?
There are two possibilities: Either the production can not be applied or every edge incident to the node that is going to be deleted is also deleted. Let us call those grammars fixed grammars and floating grammars, respectively.
In the categorical approach fixed grammars correspond to the DPO approach and floating grammars to the SPO approach.This is precisely the main difference between them. The pushout construction takes care of dangling edges in the SPO approach and the double pushout construction (DPO approach) does not allow the application of a production if any edge is going to become a dangling edge.
MGG is a floating grammar (this topic is addressed in detail in Sec. 5 of the MGG book). This is achieved using one operator, T. The basic idea is to enlarge the production p in order to include (to delete) any potential dangling edge. As it always happens up to now in MGG, an operator turns out to be equivalent to a certain sequence of productions. In case of dangling edges T(p) is equivalent to a sequence of two productions p;pe , where pe (epsilon-production or e-production) deletes any potential dangling edge (pe is applied before p). If a fixed grammar is preferred, it is enough to make T be the identity operator (compatibility is an application condition that MGG has for free).
It remains to guarantee that p and pe will be applied in the same place of the graph (recall non-determinism). To this end MGG uses marking, which is introduced in Sec. 5.2 of the MGG book.
Today I quote Thales. In my opinon, honesty is a must: I will be sufficiently rewarded if when telling it to others you will not claim the discovery as your own, but will say it was mine.
Today I touch on dangling edges. Let p be a production that specifies the deletion of one node (the LHS -- left hand side -- is made up of a single node and its RHS is empty). Suppose the production is applied to a graph with no isolated nodes. What happens with the edges that are incident to the node that p deletes?
There are two possibilities: Either the production can not be applied or every edge incident to the node that is going to be deleted is also deleted. Let us call those grammars fixed grammars and floating grammars, respectively.
In the categorical approach fixed grammars correspond to the DPO approach and floating grammars to the SPO approach.This is precisely the main difference between them. The pushout construction takes care of dangling edges in the SPO approach and the double pushout construction (DPO approach) does not allow the application of a production if any edge is going to become a dangling edge.
MGG is a floating grammar (this topic is addressed in detail in Sec. 5 of the MGG book). This is achieved using one operator, T. The basic idea is to enlarge the production p in order to include (to delete) any potential dangling edge. As it always happens up to now in MGG, an operator turns out to be equivalent to a certain sequence of productions. In case of dangling edges T(p) is equivalent to a sequence of two productions p;pe , where pe (epsilon-production or e-production) deletes any potential dangling edge (pe is applied before p). If a fixed grammar is preferred, it is enough to make T be the identity operator (compatibility is an application condition that MGG has for free).
It remains to guarantee that p and pe will be applied in the same place of the graph (recall non-determinism). To this end MGG uses marking, which is introduced in Sec. 5.2 of the MGG book.
Today I quote Thales. In my opinon, honesty is a must: I will be sufficiently rewarded if when telling it to others you will not claim the discovery as your own, but will say it was mine.
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