#yourdon

[blogsio-blog]

DFD  - Lunes 11 de marzo del 2019

La lección del día fue sobre el Diagrama de Flujos de Datos, el cual es una herramienta para visualizar mejor un sistema como una red de procesos funcionales relacionados entre sí y con almacenamientos de datos.

Los componentes son:

Entidades externas que pueden ser externas a la organizacion o internas de la organización pero externas al sistema. Se representan como un rectángulo.

Procesos: parte del sistema que transforman la entradas en salidas. Debe identificar un nivel, su nombre puede ser verbo-obejto o sustantivo y se representa como un círculo.

Fujos: representan los datos de entrada o salida o bidireccional(diálogo) que se dirigen en un sentido. Su nombre no puede ser un verbo a menos que sea un diálogo. Se representan como una flecha más su nombre. -->, <--, <---> (Hay casos en los que no se pone el nombre, como en los almacenes).

Almacenes: colección de datos. Se representan como dos líneas paralelas. Puede ser una BD, archivos digitales o físicos, datos en tarjetas, etc. Si el flujo sale del almacen es de lectura o consulta, si va hacia el almacen es de actualización.

Los métodos de elaboración de DFD son:

Método de expansión en la elaboración de DFD según Gane y Sarson. Hay un DFD general y otro detallado.

Método de explosión en la elaboración de DFD: según DeMarco y Yourdon. Hay múltiples DFDs, desde el nivel 0 que engloba a todo el sistema y sus entidades externas hasta desenglobar cada proceso principal.

          - Nivel 0: Contexto.

          - Nivel 1: Procesos principales del sistema.

          - Nivel 2: Uno de los procesos principales expandido en subprocesos.

No suelen llegar al nivel 3 ni 4 ya que lo que se quiere es simplificar la descripción de un sistema.

Importante: Los nombres de los flujos, almacenes, entidades externas y procesos deben ser simples y concisos. Los procesos deben ser numerados. Diagrama simple y fácil de entender. Evitar almacenes con sólo entradas sin generar salidas. Etiquetar los flujos.

[chillypepperhothothot]

Active driveway: no parking! by Ed Yourdon Via Flickr: On the second day of our photography class, we met in a coffee shop in the Mission District of San Francisco. A few of us spent the morning walking north, into a somewhat bleak "warehouse district" that seemed to have nobody on the street, and not much that inspired me to photograph. But the houses and buildings were somewhat interesting and colorful, especially as compared to my familiar habitat of New York City. Indeed, even the "no parking" signs were a lot more melodramatic than what I'm accustomed to seeing ... ************************ In early November 2015, I flew from New York to San Francisco to take a weekend street-photography workshop under the tutelage of Eric Kim. As you might expect, I took gazillions of photos; but not all of them were specifically associated with the workshop itself. On the way out to San Francisco, I took a bunch of pictures with my iPhone; and during the weekend, I took a number of photos that had little or nothing to do with street-photography per se. I’ll upload the photos in dribs and drabs during the next several days, and let you decide which ones are sufficiently interesting to warrant a second look…

[eyourdon]

Mother and children ************************* Sometime in early 2014, I created an album on Flickr for photos that I had started taking with my iPhone5s; and in the fall of 2014, I started a new Flickr album for photos that I had begun taking with my iPhone6, and iPhone6+. But progress doesn’t stop: as of October 2015, I’ve upgraded once again, to the iPhone6s and 6s+ (yes, both of them). The the camera now has a 12-megapixel lens (instead of the older 8 MP version), and that the internal camera-related hardware/firmware/software is better, too. Obviously, I’ve got the newer iOS9, too, and even on the “old” phones, it now supports time-lapse videos along with everything else. I’ve still got my pocket camera (an amazing little Sony RX-100 Mark IV), and two larger cameras (Sony RX-10 II, and Sony A7 II), but I have a feeling that I won’t even be taking them out of the camera bag when I’m out on the street for ordinary day-to-day walking around. That will depend, obviously, on what kind of photos and videos the iPhone6s/6s+ camera actually capable of taking … so I’m going to try to use at leas one of them every day, and see what the results look like … Stay tuned … #Yourdon #streetphotography #Manhattan #NewYork #UpperWestSide #Broadway (at Earth Café)

[eyourdon]

Crossing the street ************************* Sometime in early 2014, I created an album on Flickr for photos that I had started taking with my iPhone5s; and in the fall of 2014, I started a new Flickr album for photos that I had begun taking with my iPhone6, and iPhone6+. But progress doesn’t stop: as of October 2015, I’ve upgraded once again, to the iPhone6s and 6s+ (yes, both of them). The the camera now has a 12-megapixel lens (instead of the older 8 MP version), and that the internal camera-related hardware/firmware/software is better, too. Obviously, I’ve got the newer iOS9, too, and even on the “old” phones, it now supports time-lapse videos along with everything else. I’ve still got my pocket camera (an amazing little Sony RX-100 Mark IV), and two larger cameras (Sony RX-10 II, and Sony A7 II), but I have a feeling that I won’t even be taking them out of the camera bag when I’m out on the street for ordinary day-to-day walking around. That will depend, obviously, on what kind of photos and videos the iPhone6s/6s+ camera actually capable of taking … so I’m going to try to use at leas one of them every day, and see what the results look like … Stay tuned … #Yourdon #streetphotography #Manhattan #NewYork #UpperWestSide #Broadway (at Jeffrey Stein Salon at 86th Street)

[eyourdon]

Everyone needs a little help sometimes ************************* Sometime in early 2014, I created an album on Flickr for photos that I had started taking with my iPhone5s; and in the fall of 2014, I started a new Flickr album for photos that I had begun taking with my iPhone6, and iPhone6+. But progress doesn’t stop: as of October 2015, I’ve upgraded once again, to the iPhone6s and 6s+ (yes, both of them). The the camera now has a 12-megapixel lens (instead of the older 8 MP version), and that the internal camera-related hardware/firmware/software is better, too. Obviously, I’ve got the newer iOS9, too, and even on the “old” phones, it now supports time-lapse videos along with everything else. I’ve still got my pocket camera (an amazing little Sony RX-100 Mark IV), and two larger cameras (Sony RX-10 II, and Sony A7 II), but I have a feeling that I won’t even be taking them out of the camera bag when I’m out on the street for ordinary day-to-day walking around. That will depend, obviously, on what kind of photos and videos the iPhone6s/6s+ camera actually capable of taking … so I’m going to try to use at leas one of them every day, and see what the results look like … Stay tuned … #Yourdon #streetphotography #Manhattan #NewYork #UpperWestSide #Broadway

[eyourdon]

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Quiet lunch on a park bench in NYC ************************* Sometime in early 2014, I created an album on Flickr for photos that I had started taking with my iPhone5s; and in the fall of 2014, I started a new Flickr album for photos that I had begun taking with my iPhone6, and iPhone6+. But progress doesn’t stop: as of October 2015, I’ve upgraded once again, to the iPhone6s and 6s+ (yes, both of them). The the camera now has a 12-megapixel lens (instead of the older 8 MP version), and that the internal camera-related hardware/firmware/software is better, too. Obviously, I’ve got the newer iOS9, too, and even on the “old” phones, it now supports time-lapse videos along with everything else. I’ve still got my pocket camera (an amazing little Sony RX-100 Mark IV), and two larger cameras (Sony RX-10 II, and Sony A7 II), but I have a feeling that I won’t even be taking them out of the camera bag when I’m out on the street for ordinary day-to-day walking around. That will depend, obviously, on what kind of photos and videos the iPhone6s/6s+ camera actually capable of taking … so I’m going to try to use at leas one of them every day, and see what the results look like … Stay tuned … #Yourdon #streetphotography #Manhattan #NewYork #UpperWestSide #Broadway (at 96th Street)

[eyourdon]

View this post on Instagram

Christmas trees on a quiet New York street ************************* Sometime in early 2014, I created an album on Flickr for photos that I had started taking with my iPhone5s; and in the fall of 2014, I started a new Flickr album for photos that I had begun taking with my iPhone6, and iPhone6+. But progress doesn’t stop: as of October 2015, I’ve upgraded once again, to the iPhone6s and 6s+ (yes, both of them). The the camera now has a 12-megapixel lens (instead of the older 8 MP version), and that the internal camera-related hardware/firmware/software is better, too. Obviously, I’ve got the newer iOS9, too, and even on the “old” phones, it now supports time-lapse videos along with everything else. I’ve still got my pocket camera (an amazing little Sony RX-100 Mark IV), and two larger cameras (Sony RX-10 II, and Sony A7 II), but I have a feeling that I won’t even be taking them out of the camera bag when I’m out on the street for ordinary day-to-day walking around. That will depend, obviously, on what kind of photos and videos the iPhone6s/6s+ camera actually capable of taking … so I’m going to try to use at leas one of them every day, and see what the results look like … Stay tuned … #Yourdon #streetphotography #Manhattan #NewYork #UpperWestSide #Broadway (at Earth Café)

[eyourdon]

Sometimes New Yorkers have to remind themselves where they are ************************* Sometime in early 2014, I created an album on Flickr for photos that I had started taking with my iPhone5s; and in the fall of 2014, I started a new Flickr album for photos that I had begun taking with my iPhone6, and iPhone6+. But progress doesn’t stop: as of October 2015, I’ve upgraded once again, to the iPhone6s and 6s+ (yes, both of them). The the camera now has a 12-megapixel lens (instead of the older 8 MP version), and that the internal camera-related hardware/firmware/software is better, too. Obviously, I’ve got the newer iOS9, too, and even on the “old” phones, it now supports time-lapse videos along with everything else. I’ve still got my pocket camera (an amazing little Sony RX-100 Mark IV), and two larger cameras (Sony RX-10 II, and Sony A7 II), but I have a feeling that I won’t even be taking them out of the camera bag when I’m out on the street for ordinary day-to-day walking around. That will depend, obviously, on what kind of photos and videos the iPhone6s/6s+ camera actually capable of taking … so I’m going to try to use at leas one of them every day, and see what the results look like … Stay tuned … #Yourdon #streetphotography #Manhattan #NewYork #UpperWestSide #Broadway (at Walgreens)