## UML Deployment diagram, what does the deploy dependency mean?

When a deployment diagram shows an artifact deployed on a node (with either the deploy dependency arrow or one of the alternative way to draw the relationship).

• Does it mean that the artifact exists on the node (such as in the file system of a computer)?
• Or, does it mean that the node is executing the artifact (such as an exe or a python file being executed) ? And in this case, how can i modeled one artifact being executed twice (or more) on the same node?

## database design – How to represent foreign key in an ER diagram in Chen notation?

This is a spin-off of the question at How to represent foreign key in an ER diagram? which is too vague about the notation it asks for.

There the idea of underlining FKs with a dotted line is stated. I also remember this from an exam. I have searched a bit, finding that a dotted line represents a weak key attribute.

Source: https://conceptdraw.com/a977c4/p1/preview/640/pict–chen’s-erd-design-elements—er-diagram-(chen-notation).png–diagram-flowchart-example.png

Can I use this notation to show FKs in an ERD in Chen notation?

## dnd 5e – Is the DMG 3/4 cover diagram incorrect?

### Their example just illustrates their point, it does not imply that it is impossible to avoid 3/4 from that position, only from that corner

I believe this is just supposed to be an illustrative example. If you choose the corner they chose on that image, then the target has 3/4 cover, but if you choose the corner that you chose, then the target only has half cover.

I don’t think their example was supposed to imply that the character has no way to get around the 3/4 cover in that example, simply that by choosing the corner that they chose, they can show you what 3/4 cover looks like (on a grid).

That said, your observation is a good one; they might have been better off choosing the square above so that 3/4 cover is the best you can achieve from that position.

## How to read constellation diagram?

I initially tried to read this constellation diagram https://doi.org/10.1371/journal.pcbi.1003588.g010. I read the entire explanation below the figure, but when I try to associate the histogram to the diagram graph, I cannot understand the logic for locating each "concept" in the diagram. I have been reading but I still don’t understand. Here is a simpler example perhaps on the same subject https://www.nature.com/articles/nrn.2016.44#Fig1, additionally also read the respective explanation at https://www.nature.com/articles/nrn. 2016.44.

## time complexity – Minimize shadows placing light sources on a diagram of a room

I’m a CS student and came upon this problem:

Given a diagram of a room with obstacles in it (like walls or furniture), find the 4 best places to put light sources in it so the room has the most light possible, or you can think of, minimizing the amount of shadow in the room.

In other words, if you have 4 sources of light, which are the best places to put them so your room has maximum light (or minimum shadow).

I’ll append an example of a diagram so the problem can be better understood: example of a diagram

The solution I thought was to find the spot with most light and from there find the second one and so on. But something makes me think that it may exist a configuration which is better that doesn’t need to be the best from the beginning, kinda feels like a special case of the knapsack problem, if so I’d think of implementing a greedy algorithm or using genetic algorithms to give an approximation of the best places.

I’m not sure if it’s a math or a CS problem. I’d be grateful if at least someone points me in the right direction so I can do a better research, thank you very much!

## data – Problem plotting a bifurcation diagram of logistic map

I would like to plot a bifurcation diagram from the logistic map (difference equation) of the type

$$x_{t+1} = r,(1-x_{t}),x_{t}.$$

The code I used for that was

``````r1 = Table(i, {i, 0.1, 4, 0.0001});
sol = Table(
RecurrenceTable({x1(t + 1) == r1((i)) (1 - x1(t)) x1(t),
x1(0) == 0.2}, x1,
{t, 1000}), {i, Length(r1)});
list1 = Table({r1((i)), Last(sol((i)))}, {i, Length(sol)});
ListPlot(list1,
AxesLabel -> {"r", "N"},
PlotRange -> {{0.1, 4}, {0.1, 1}})
``````

However, the result is deformed, as follows

I expected a result like,

Could anyone tell me what happened?

## domain driven design – When bounded contexts and “microservices” collide. A distributed systems dilemma in diagram form

You can’t please everyone. Some people want a lot of context and background on sites like this. Others do not. If you don’t want the background, skip the first three paragraphs.

I am a software architect with about 25 years experience, starting with Amiga Basic, then C, then C++, VB6, delphi, C#, SQL (server), and more C#. Over the last 15 years my focus has been on back ends – databases, data models, and systems integration (not UI development, and certainly not modern web development with giant javascript libraries)

I currently work in a reasonably large “enterprise”. By “enterprise” I mean “not a software development company”. By “reasonably large” I mean our software ecosystem includes such things as an ERP (vendor code), a CRM system (vendor), an HR system (vendor), a few other vendor systems, a data warehouse, a BI stack, and a rapidly growing number of internally developed applications.

The number of internally developed applications is growing rapidly because the business wants to be able to add new functionality that is specific to us, providing market advantages, or just being able to move faster than the large vendors providing our monolithic systems. I expect this story will be familiar to many, although it probably won’t be quite so familiar to people working for pure software development companies, where you don’t have to deal with the problem of integrating with large vendor systems. If you fall into the latter category, please keep this in mind.

Enough general background.

I have been deeply studying just about everything to do with microservices, event driven architectures, ESBs, message brokers, and other integration elements at a hectic rate over the last several months, as well as rereading Evan’s “DDD”, Vernon’s “Implementing DDD”, Hohpe and Woolfe’s “Enterprise Integraiton Patterns”, and other famous books. And I have noticed a problem.

There are several different “primary sources” or “patterns” of advice on this topic. They all make good points. And they all contradict each other somewhere. I believe I can make the similarities and differences obvious with some simple diagrams.

Of course, the big question is “what do you want to achieve?”. Well, let’s settle on things everyone seems to agree on with distributed systems: Given CAP, we are very interested in A and P, not so much C. Eventual consistency is accepted, but we don’t want one system to bring down all the rest, and we do want to partition the systems – for example into bounded contexts per Eric Evans’ DDD.

So, I want you to picture what at first seems to be a fairly “ideal” architecture according to many high profile sources, by which I mean it hits all the right notes. We have an order entry (point of sale) system. It’s a bounded context. We’re not “trying too hard to be microservicey” and creating nanoservices, and we’re also not a distributed monolith. It’s effectively agnostic about the existence of any other system in the enterprise. It’s as decoupled as it can possibly be. It has no hard temporal, logical, or availability dependencies on any other system. It looks something like this:

One day the business comes along and says “I want order entry (or quoting) functionality in the CRM system”.

Shit.

Now I think I can describe everything else I need to describe purely with a set images which illustrate the various approaches I’ve seen advocated over countless books, blogs, articles, lectures, and videos, making the distinction between them clear. I have never seen the options laid out quite this way, and I think doing so demonstrates that as an industry we don’t seem to have any “logically sound” solution which meets all of our principles of software architecture – except maybe the last. And I would like to hear people’s opinions on what they see.

Personally, I think option 6 is the most – and perhaps only – sane choice. In a couple of places I mention that shared library/schema definitions are “probably not a real objection”. I say this because the business rules are the business rules. There’s only one set of business rules for the bounded context of orders. If the business rules change, everyone using those rules has to change. This isn’t a devops issue.

## java – Use Case Diagram for Vending machine

I want to create a use case diagram for a vending machine which has the following states:

Accepts coins of 1,5,10,25 Cents
Allow user to select products Coke(25), Pepsi(35), Soda(45)
Allow user to take refund by canceling the request.
Return selected product and remaining change if any
Allow reset operation for vending machine supplier.
Its my first time that i try to create a use case diagram and i tried to implement that

Its the first time that im trying to create a uml. Can anyone help me to create it?

## database design – What kind of Relations should I have in my E/R Diagram

I am trying to create an Entity/Relationship Chen Diagram for a new APP. Scope is simple enough.

I will have multiples types of users login through the same Login Form.

What I decided to do… Is create a parent Table call Credentials that will contain only the Username/Email & Password.

Users, Subcontractors, Clients & Employees will have access to the system but each of those tables will have diferents attributes, that’s why I need differents table. But all of them will have a Username/Email & Password.

I guess that is a Hierarchy relationship. And the relations should be I guess…

• 1 Credentials to 1 Users.
• 1 Credentials to 1 Subcontractors.
• 1 Credentials to 1 Clients.
• 1 Credentials to 1 Employees.

I am doubting a lot.

1. How can I represent that in a E/R properly?, Is this way a good way to do it?
2. In children tables Should I use the Credentials ID as primary key?
or is better to use Credentials ID as foreign key but have primary
key as well?
3. Children… are week entities right?
4. If for example… a Subcontractor will required differents account to login… different should be… create a NM?

## fast fourier transform – Butterfly diagram from cooley-tukey algorithm

I am trying to understand the logic of this algorithm so i can implement my own but i am not understanding this diagram i see appearing many times in a fair few articles on the topic, i am teaching myself so i don’t have a computer science degree to help. But i understand the general idea behind the algorithm.

But this butterfly diagram is confusing me.

How do you interpret this diagram from left to right mathematically speaking? It’s so confusing.. what are the arrows telling me to do in terms of math operations on the functions?