Scalable VS Extensible [closed] - system

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I'm not sure if this type of question is allowed here, but it is related to software projects.
Is there a difference between scalable and extensible?
Is extensible a sub-set of scalable? I.e. Scalable (extensible)
Some regard it as the same, others regard it as different. What are the differences?
I am led to believe:
Scalable - make the system withstand more usage (bandwidth etc...) AND make it larger.
Extensible - add more functionality to the system.
Are they not the same?
Edit: If extensible is adding more functionality to the system and scalable can be deemed as making a system larger, is that not theoretically the same, proving that extensible is just a sub-set of scalable?

I am not a native speaker but I do think there is a difference.
If sth. is scalable, that means it can adopt to growth. This does not say how it adopts (that is, either by being so well-fitted already that it could take more requests, or by adding more resources of the same type, or by easily changing components).
Wikipedia says:
[It is the] ability to be enlarged to accommodate [some kind of] growth.
In theory it might also refer to a "downsizing" but that is normally not so interesting from an IT point of view.
You proposed:
Extensible - add more functionality to the system.
Possibly, but not necessarily. It might also refer to adding more capacity that serves the same purposes as before.
I'd say:
Scalability means a system is able to accomodate growth. I.e. the system grows.
Extensibility means you are able to (easily) add something to the system. I.e. something new is attached to the system - which does not have to be growth-related.

Agree with Observer. Just to add few more examples:
Extensibility:
How easily your software can support 'hooks' for new functionalities, interfaces, devices, input types etc.
This might also refer to how easily your software can support new services with least/no disruption to existing code and clients. For example, addition of a new endpoint to an existing webservice can be considered as a dimension of extensibility.
Scalability:
How easily your software will be able to deal with growing userbase / additional data, etc. Example: If your userbase grows in future, or you decide to save additional data for each entity, is your database scalable? Is your software scalable to user base growth?
When it comes to scalability, we also start talking about horizontal Vs vertical scalability and both of these are primarily referring to whether the system can scale on same infra/instance/deployment (vertical scalability) or we need to add some 'peers' to be able to take more load (horizontal scalability).

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Database documentation and reverse engineering [closed]

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I know this question has been asked in various forms over and over again but I cannot find a single complete answer and I believe it is a general problem in the RDBMS/data area and industry. To explain the problem I will tell you a short (and maybe boring) story!
The Story
"I have a friend" who works in A company that uses 100+ systems. The scale and size of these systems vary from full-blown ITIL to custom/in-house, single purpose, LAMP/SQLite/CSV-based solutions. The vast majority of these systems, at one point or another use a database/data-store... Big-data has now become a trend, and A company though it is a very good idea to keep (or log) historical data from all systems forever! For that reason they have built a "warehouse". My friend is responsible for writing software that will do the analysis on some of this data ... however, he is kinda confused. There are thousands of tables in that warehouse containing data from the beginning of time (1970s I think :)).
The Problem
[Since I started telling you about this guy, I should probably continue]
My friend is very upset because of the lack of documentation in that warehouse. It seems that no-one knows what is what?! Few of the problems he faces (and I quote):
Man, some fields are constants... they have a special meaning to the application but I have no way of knowing? But that is OK... cause some other fields are bit-masks! Different bit values in the field have different meaning!
and he continues...
That's not all... these are the easy cases you know... Since we have data from multiple systems, we end up with a situation where different systems refer to the same thing in a different way... how can I explain it to you... for example, a network device has an FQDN, however some systems treat it as the primary key, some others don't and instead they allocate an auto-increment integer value, which in turn they use for foreign keys (you know... referencing this device).
and he can go on forever!
The Question
[Yes, it is one question]
He says:
We have come a long way regarding documentation in the software world... we have started with documents, moved to wikis and concluded to inline docblocks serving both as parameter/signature documentation and as wiki! We can auto-generate documentation, clear enough that a person in the other hemisphere and side of this world can easily follow!
and he continues:
... in the data side of things, we also had major achievements! Storage methods, serialization, transmission and data analysis techniques have evolved tremendously... We have also managed to map database tables into objects and in some cases we can even represent relationships!
So why the frell don't we have a standard method/technique of documenting our data structures in an RDBMS?
... he concluded :)
Enough with my friend, so my comments:
I know about comments on fields in various systems, but that is usually enough for a "deprecated" and not for an explanation
Updating a wiki or even worse a document, every time you release a database patch is not a solution... that patch should contain the relevant documentation!
ER diagrams can be easily generated based on the schema information, however this is not the easiest form of documentation to read... for anything more than 10 tables!
There is the saying (please comment if you know who said this! - respect)
Documentation is like sex: when it is good, it is very, very good; and when it is bad, it is better than nothing
Why SQL doesn't provide the means to any?
Any kind of documentation would get stalled if not maintained.
Also, the SQL world provides all kind possibilities to document things:
comments in SQL files
comments in columns/tables metadata
as you said - E/R diagrams
the classic way of documenting stuff - docs and wikis
good discipline in adhering to an intuitive naming scheme for the things in DB - I think this should be the standard
We have all the tools we need, we just have to convince our managers to let us write the docs (lol)

To collaborate or to compete? [closed]

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I work on developer tools for a particular product. There is a competing set of tools for the same product produced by a different company. The user-base is split roughly 50-50 between us.
Recently, the other company has introduced scripting to make their own tools extensible by end-users. This is a feature that we have had planned for our tools for a while, but it is only now that we are able to start implementing it.
My question is: should we try as much as possible to collaborate with the developers of competing product so that end-user scripts can be shared between users on the different products? We would obviously require different implementations, but share the same syntax. This would obviously be better for the community as a whole since there would be more interoperability.
The downside of collaborating like this is that the competing product's scripting language is slightly tailored towards their own implementation. We would have to jump through a few hoops to create an implementation for their scripts on our platform. Or, we would have to somehow convince our competitor to modify their scripts so that they are platform agnostic.
So, to rephrase my question: should we try to collaborate, thus making our community happier, or should we produce a competing scripting language that is more appropriate for our platform?
I realize that this is a very general question with no single right or wrong answer. What I am looking for is a good explanation of the pros and cons of each approach.
I would write something that is specifically tailored towards my own system (don't compromise your technical quality) and then release and fully support a compatibility layer that allows my competitors scripts to run on my system (make it easy for users to migrate).
I'd stay away from doing things that will try to lock people in and cripple them if they move. These tactics worked once upon a time but in this day and age don't really cut it any more. I'd even go so far as to actually (unofficially on fora etc.) help people who are having trouble porting scripts running on my system to my competitors.
Another way to ask the question (and to answer) is to wonder WHAT KIND of script language is DESIRABLE FOR USERS.
If your competitor went a lock-in route with a proprietary scripted language, then please your users (and get a competitive edge) by using a STANDARD scripted language.
Doing so will immensely increase the value of your tool as many persons ALREADY know the scripted language.
Nobody wants to learn a new language.
Would building a unified scripting language harm your customer-base or give the competitor the competitive edge?
Obviously if you want to lock in customers, go solo which will prevent your customers from easily switching over to the competitor's product (sounds a little like Microsoft tactics) or if you know your product is superior, a collaboration will allow you to get customers from the competitor in which case customers will have the choice to choose which business model suits their needs, make a choice based on the quality of the product as a whole as well as which features they really need instead of being locked into an invisible contract due to the choice they made initially.
Going the collaboration route will also put your company in a position where developers will respect your company (for not being a greedy monopoly monster) instead of boycotting it due to their "moral" beliefs in open standards.
I would say that if possible make it compatible, not so much to cooperate but to compete. Making an incompatible solution would lock you customers in to some degree (you don't have any yet with a lot of scripts - so not much gain), but making a compatible solution keeps the door open for customers of your competition to migrate (they might have some scripts by the time you ship yours).
Just my 2cents

need help for planning software development , database design [closed]

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I have been doing a coding in for last 7 months. Most part of it has been the updations to the very poorly coded software in asp. Now I am going to redevelop entire software in asp.net. I want it to be very efficient. I need some tips and guidance about how to plan project and design a good database. Thanks in advance for help.
As far as planning for the project is concerned you first need to create your application's pages on paper. Write all your ideas on the paper.
Draw each and every page on paper and complete it with your new ideas.
Then taking every page's feature into consideration draw the database tables. This is a very careful phase. So include every aspect of your application's functionality.
For designing the database follow these steps :
List all entities
Find Relationships [E-R matrix]
Draw Cardinality
Define Primary keys
Draw ERD
Eliminate many-to-many relationships
Identify attributes [attribute entity matrix]
Map attributes - only 1:1 with each entity
Draw final ERD
More help here
Structured process you must know to develop a web application
Here's my super-quick spiel about database design.
A database is two things. It is a 'logical engine', and it is a 'physical engine'. It is a logical engine in that it allows you to create meaningful models of entities. It is a physical engine in that it processes bits of data to update or return results.
I suggest paying about equal attention to each of these aspects when designing a new system. To adress the first, work out the relational model and normalize as far as possible. To address the second, think about where you might want to denormalize for speed, what indexes you'll need to speed the processing, etc.
It's good that you ask, this is one of the most anti intuitive things in software development. My approach would be: pick one feature, implement it in ASP.NET, and convince your users to move over. You'll be surprised how many things you missed, or how actual performance compares to developer testing.
The quicker you iterate, the better your replacement project will be, and the less time you spend on things that don't really matter. There's a excellent blog post at Coding Horror about this; it's called Boyd's Law of Iteration.

Any tips for creating a key value store abstraction layer? [closed]

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With all the key value data stores out there I have started to create an abstraction layer so that a developer does not have to be tied in to a particular store. I propose to make libraries for:
Erlang
Ruby
Java
.NET
Does anyone have any tips on how I should go about designing this API?
Thanks
First off, and as a general rule for anytime you build "pluggable" abstraction layer, build it to support at least two real implementations to start. Don't build it for just one datastore and try to make it abstracted, because you'd overlook a details that won't plug into another implementation very well. By forcing it to use two seperate implementations, you'll get closer to something that is actually flexible, but you'll have to make further changes to support a third and fourth data store.
Second, don't bother, these things already exist. Microsoft has provided a ton of these for their technologies (ODBC, ADO, ADO.NET, etc), and I'm sure Ruby/Java/etc has several as well. I understand the desire to encapsulate the already existing technology, but the more data stores you need to support, the more complexity you need to build in, and the closer you'll get to ADO.NET (or similar technologies). Companies like MS have spent a ton of money and research on solving this exact problem, and that is what they came up with.
I would strongly recommend checking out Twitter's Storehaus project - this is a key-value store abstraction layer for the JVM and written in Scala, supporting (to date) Memcache, Redis, DynamoDB, MySQL, HBase, Elasticsearch and Kafka.
Storehaus's core module defines three traits:
A read-only ReadableStore with get, getAll and close
A write-only WritableStore with put, putAll and close
A read-write Store combining both
In the Ruby ecosystem, you should check out moneta, which again provides a unified interface to key/value stores. It has a lot more features than Storehaus.

How to document applications and how they integrate with other applications? [closed]

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As the years go by we get more and more applications. Figuring out if one application is using a feature from another application can be hard. If we change something in application A, will something in application B break?
We have been using MediaWiki for documentation, but it's hard to keep the data up-to-date.
I think what we need is some kind of visual map of everything. And the possibility to create some sort of reference integrity? Any ideas?
I'm in the same boat and still trying to sell my peers on Enterprise Architect, a CASE tool. It's a round trip tool - code to diagrams to code is possible. It's a UML centric too - although it also supports other methods of notation that I'm unfamiliar with...
Here are some things to consider when selecting a tool for documenting designs (be they inter-system communication, or just designing the internals of a single app):
Usability of the tool. That is, how easy is it to not only create, but also maintain the data you're interested in.
Familiarity with the notation.
A. The notation, such as UML, must be one your staff understands. If you try using a UML tool with a few people understanding how to use it properly you will get a big ball of confusion as some people document things incorrectly, and someone who understands what the UML says to implement either spots the error, or goes ahead and implements the erroneously documented item. Conversely more sophisticated notations used by the adept will confound the uninitiated.
B. Documentation isn't/shouldn't be created only for the documenters exclusive use. So those who will be reading the documentation must understand what they're reading. So getting a tool with flexible output options is always a good choice.
Cost. There are far more advanced tools than Enterprise Architect. My reasoning for using this one tool is that due to lack of UML familiarity and high pressure schedules, leaves little room to educate myself or my peers beyond using basic structure diagrams. This tool easily facilitates such a use and is more stable than say StarUML. (I tried both, StarUML died on the reverse engineering of masses of code -- millions of lines) For small projects I found StarUML adequate for home use, up until I got vista installed. Being opensource, it's also free.
With all that said, you will always have to document what uses what, that means maintaining the documentation! That task is one few companies see the value in despite its obvious value to those who get to do it. . .