In the book Artificial Intelligence: A Modern Approach, ch 3, the first question asks why a problem-solving agent (search) needs to formulate the goal first and then formulate the problem. My guess is that the agent needs to formulate the goal first in order to decide on the level of abstraction of the actions it is going to use in the problem solving process (not in reality). The problem is usually a graph with an initial state and a final state (goal) and the agent must find a sequence of actions that lead to the goal.
Thank you,
I think you're making it too complicated. If the form of the problem is already given to the agent (as a set of state changing actions that will form the graph), then it needs to know what the goal is (i) to have a decision procedure for "am I done yet?" - i.e. "is the state I've just planned or observed the goal state", and (ii) as a reference point for heuristically-guided search. If, for example, you were using A* you need some way of estimating the distance to the goal for a given search state, so by corollary you need to know what the goal state is first.
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I am new in doing an activity and currently, I am trying to draw one based on given description.
I enter into doubt on a particular section as I am unsure if it should be 'split'.
Under the "Employee", the given description is as follows:
Employee enter in details about physical damage and cleanliness on the
machine. For the cleanliness, there must be a statement to indicate
that the problem is no longer an issue.
As such, I use a foreach as a means to describe that there should be 2 checks - physical and cleanliness (see diagram in the link), before it moves on to the next activity under the System - for the system to record the checks.
Thus, am I on the right track? Thank you in advance for any replies.
Your example is no valid UML. In order to make it proper you need to enclose the fork/join in a expansion region like so:
A fork/join does not accept any sematic labels. They just split the control flow into several parallel ones which join at the end.
However, this still seems odd since you would probably have some control for the different inspections being entered. So I'd guess there's a decision which loops through multiple inspection entries. Personally I use regions only for handling interrupts. ADs are nice to a certain level. But sometimes a tabular text (like suggested by Cockburn) is just easier to write and read. Graphical programming is not the ultimate answer (unlike 42).
First, the 'NO' branch of the decision node must lead somewhere (at the end?).
After, It differs if you want to show the process for ONE or MULTIPLE inspections. But the most logical way is to represent the diagram for an inspection, because you wrote inspection without S ! If you want represent more than one inspection, you can use decision and merge node to represent loop that stop when there is no more inspection.
I have considered making a new requirement stereotype for which I can make threshold and objective attributes. That is fine as far as capturing the requirement goes, but then becomes ugly when trying to do verification. I'm starting to think they must be captured as separate requirements, which may also be ugly when doing traceability, satisfactions and verifications.
For example, my requirement says "The system shall be no more than 100kg. (T)" and "The system shall be no more than 80kg. (O)"
Tracing this (or a similarly stated requirement) becomes "ugly" when making a test plan and showing which requirement has been satisfied. If (O) is satisfied, then clearly (T) is also. However, the system will still pass test even though it may fail the verification for (O). Perhaps it is standard to carry some requirements (O) that are not met. I am new to this modeling method-so just curious. I wanted to know if there is already a best practice out there. I have been looking and haven't found anything that addresses this.
From what I understood, you want to model, that a certain performance requirement has two values, a threshold and an objective. Meeting the objective is optional, but meeting the threshold is mandatory. In the test plan, the requirement will be shown as satisfied, if the design meets the threshold. Whether it also meets the objective could be evaluated with a model report, but that is only informative and doesn’t have any effect on the test outcome.
I would create a new stereotype «performance requirement» specializing «abstractRequirement» and «ConstraintBlock» (as described in the SysML specification Annex E.8.2). When you use this Stereotype, you need to add three parameters: actualMass, thresholdMass and objectiveMass. The constraint will be {actualMass<thresholdMass}. The objectiveMass is then just informative (I have to think it through, how this could get used for reporting).
Another possibility would be to add a mandatory/optional field to the performance stereotype and use optional for objectives.
It is my first time doing a Petri net, and I want to model a washing machine. I have started and it looks like this so far:
Do you have any corrections or help? I obviously know its not correct, but I am a beginner and not aware of the mistakes you guys might see. Thanks in advance.
First comments on your net's way of working:
there is no arrow back to the off state. So once you switch on your washing machine, won't you never be able to switch it off again ?
drain and dry both conduct back to idle. But when idle has a token, it will either go to delicate or to T1. The conditions ("program" chosen by the operator) don't vanish, so they would be triggered again and again.
Considering the last point, I'd suggest to have a different idle for the end of the program to avoid this cycling. If you have to pass several times through the same state but take different actions depending on the progress, you have to work with more tokens.
Some remarks about the net's form:
you don't need to put the 1 on every arc. You could make this more readable by Leaving the 1 out and indicating a number on an arc, only when more than one tokens would be needed.
usually, the transitions are not aligned with the arcs (although nothing forbids is) but rather perpendicular to the flow (here, horizontal)
In principle, "places" (nodes) represent states or resources, and "transitions" (rectangles) represent an event that changes the state (or an action that consumes resources). Your naming convention should better reflect this
Apparently you're missing some condition to stop the process. Now once you start your washing will continue in an endless loop.
I think it would be nice to leave the transition graphics unshaded or unfilled if it is not enabled. Personally I fill it green if it is enabled.
If you want someone to check if you modeled a logic properly in your Petri Net then it would be nice if you include a description of your system logic in prose.
I'm using CQRS on an air booking application. one use case is help customer cancel their tickets. But before the acutal cancellation, the customer wants to know the penalty.
The penalty is calculated based on air rules. Some of our provider could calculate the penalty through exposing an web service while the others don't. (They publish some paper explaining the algorithm instead). So I define a domain service
public interface AirTicketService {
//ticket demand method
MonetaryAmount penalty(String ticketNumber);
void cancel(String ticketNumber, MonetaryAmount penalty);
}
My question is which side(command/query) is responsible for invoking this domain service and returning result in a CQRS style application?
I want to use a Command: CalculatePenlatyCommand, In this way, it's easy to resuse the domain model, but it's a little odd because this command does not modify state.
Or should I retrieve a readmodel of ticket if this is a query? But the same DomainService is needed on both command and query side, it's odd too.
Is domain derivation a query?
There is no need to shoehorn everything in to the command-query pipeline. You could query this service independently from the UI without issuing a command or asking the read-model.
There is nothing wrong with satisfying a query using an existing model if it "fits" both the terminology and the structure of that model. No need to build up a separate read model for that purpose. It's not without risk, since the semantics and the context of the query should be closely tied to the model that is otherwise used for write purposes only. The risk I allude to is the fact that the write and read concerns could drift apart (and we're back at square one, i.e. the reason why people pick CQRS in the first place). So you must keep paying attention as new requirements come in.
Queries that fit this model really well are what I call "simulators', where you want to run a simulation using current state to e.g. to give feedback to an end user. On more than one occasion I've found that the simulation logic could be reused both as a feedback mechanism and as an execution (of a write operation/command) steering mechanism. The difference is in what we do with the outcome of the simulation. Again, this is not without risk and requires careful judgement.
You may bring arguments that Calculate Penalty Command is not odd at all.
The user asks the system to do something - command enough.
You can even have a Penalty Calculation Requested Event event in your domain, and it would feel right. Because, at some time, you may be interested in, let's say, unsure clients, ones that want to cancel tickets but they change their mind every time etc. The calculation may be performed asynchronously, too - you can provide the result (penalty cost) to the user in various ways afterwards...
Or, in some other way: on your ticket booked event, store cancellation penalty, too. Then, you can make that value accessible any time, without the need to recompute it... But this may be wrong (?) because penalty would largely depend on time, right (the late you cancel your ticket, the more you pay)?
If all this would like over-complications etc., then I guess I agree with rmac's answer, too :)
I'm writing a bridge between the user and a search engine, not a search engine. Part of my value added will be inferring the intent of a query. The intent of a tracking number, stock symbol, or address is fairly obvious. If I can categorise a query, then I can decide if the user even needs to see search results. Of course, if I cannot, then they will see search results. I am currently designing this inference engine.
I'm writing a parser; it should take any given token and assign it a category. Here are some theoretical English examples:
"denver" is a USCITY and a PLACENAME
"aapl" is a NASDAQSYMBOL and a STOCKTICKERSYMBOL
"555 555 5555" is a USPHONENUMBER
I know that each of these cases will most likely require specific handling, however I'm not sure where to start.
Ideally I'd end up with something simple like:
queryCategory = magicCategoryFinder( query )
>print queryCategory
>"SOMECATEGORY or a list"
Natural language parsing is a complicated topic. One of the problems here is that determining what a word is depends on context and implied knowledge. Also, you're not so much interested in words as you are in groups of words. Consider, "New York City" is a place but its three words, two of which (new and city) have other meanings.
also you have to consider ambiguity, which is once again where context and implied knowledge comes in. For example, JAVA is (or was) a stock symbol for Sun Microsystems. It's also a programming language, a place and has meaning associated with coffee. How do you classify it? You'd need to know the context in which it was used.
And if you can solve that problem reliably you can make yourself very wealthy.
What's all this in aid of anyway?
To learn about "tagging" (the term of art for what you're trying to do), I suggest playing around with NLTK's tag module. More generally, NLTK, the Natural Language ToolKit, is an excellent toolkit (based on the Python programming language) for experimentation and learning in the field of Natural Language Processing (whether it's suitable for a given production application may be a different issue, esp. if said application requires very high speed processing on large volumes of data -- but, you have to walk before you can run!-).
You're bumping up against one of the hardest problems in computer science today... determining semantics from english context. This is the classic text mining problem and get into some very advanced topics. I thiink I would suggest thinking more about you're problem and see if you can a) go without categorization or b) perhaps utilize structural info such as document position or something to give you a hint (is either a city or placename or an undetermined) and maybe some lookup tables to help. ie stock symbols are pretty easy to create a pretty full lookup for. You might consider downloading CIA world factbook for a lookup of cities... etc.
As others have already pointed out, this is an exceptionally difficult task. The classic test is a pair of sentences:Time flies like an arrow.Fruit flies like a bananna.
In the first sentence, "flies" is a verb. In the second, it's part of a noun. In the first, "like" is an adverb, but in the second it's a verb. The context doesn't make this particularly easy to sort out either -- there's no obvious difference between "Time" and "Fruit" (both normally nouns). Likewise, "arrow" and "bananna" are both normally nouns.
It can be done -- but it really is decidedly non-trivial.
Although it might not help you much with disambiguation, you could use Cyc. It's a huge database of what things are that's intended to be used in AI applications (though I haven't heard any success stories).