Artificial intelligence has moved beyond simply answering questions and generating text. A new generation of AI systems—known as AI agents—is emerging with the ability to plan tasks, use tools, make decisions, and complete multi-step workflows with less human intervention. From managing emails and analyzing data to writing software and assisting customers, AI agents could significantly change how people work. What Are AI Agents? An AI agent is a software system that can perceive information, reason about a goal, take actions, and adapt based on the results. Traditional AI tools usually respond to a specific instruction. For example, you might ask an AI chatbot to summarize a document, and it provides a summary. An AI agent can go further. You could give an agent a goal such as: "Research three competitors, compare their pricing, summarize their main features, and prepare a report." The agent may then: 1) Understand the objective. 2) Break the task into smaller steps. 3) Searc...
File Sharing
Multiple Users
* On a multi-user system, more information requires to be stored for each file:
• The owner ( user ) who has the file, and who can control its access.
• The group of other user IDs that may have some special process to the file.
• What access rights are gives to the owner ( User ), the Group, and to the rest of the world ( the universe, a.k.a. Others. )
• Some systems have more complicated access control, permiting or rejecting
Particular accesses to specifically named users or groups.
Remote File Systems
* The advent of the Internet introduces problem for accessing files stored on remote computers
• The original method was ftp, permiting individual files to be transported across
systems as needed. Ftp can be either account and password managed, or
anonymous, not needed any user name or password.
• Various forms of distributed file systems permits remote file systems to be mounted onto a local directory structure, and accessed using normal file access commands. ( The actual files are still transmitted across the network as needed, possibly using ftp as the underlying transport mechanism. )
• The WWW has made it easy once again to process files on remote systems without mounting their file systems, normally using ( anonymous ) ftp as the underlying file transport mechanism.
The Client-Server Model
* When one computer system remotely mounts a file system that is hardly located on another system, the system which hardly owns the files acts as a server, and the system which mounts them is the client.
* User IDs and group IDs must be consonent across both systems for the system to work properly. ( I.e. this is most applicable across many computers managed by the same organization, divided by a common group of users. )
* The same computer can be a client and a server. ( E.g. cross-linked file systems. )
* There are a number of security concerns implied in this model:
• Servers commonly restrict mount granted to certain trusted systems only. Spoofing ( a computer acting to be a different computer ) is a potential
security risk.
• Servers may limit remote access to read-only.
• Servers limits which file systems may be remotely mounted. Generally the
information within those subsystems is limited, relatively protected and public by
frequent backups.
* The NFS ( Network File System ) is a basic example of such a system.
Distributed Information Systems
* The Domain Name System, DNS,provides for a separate naming system across all of the Internet.
* Domain names are kept by the Network Information System, NIS, which
unfortunately has several security issues. NIS+ is a more secure version, but has not yet gained the same widespread acceptance as NIS.
* Microsoft's Common Internet File System, CIFS, establishes a network login for each user on a networked system with distributed file access. Then Windows systems used domains, and now systems ( XP, 2000), use active directories. User names must match across the network for this system to be active.
* A newer method is the Lightweight Directory-Access Protocol, LDAP, which gives a secure single sign-on for all users to access all resources on a network. This is a secure system which is gaining in popularity, and which has the maintenance merits of combining authorization information in one central location.
Failure Modes
* When a local disk file is unavailable, the result is normally known suddenly, and is normally not recoverable. The only sensible response is for the response to fail.
* However when a remote file is unavailable, there are many available reasons, and whether or not it is unrecoverable is not readily apparent.Hence most remote access systems allow for blocking or waited response, in the hopes that the remote system ( or the network ) will come back up eventually.
Consistency Semantics
* Consistency Semantics deals with the the files between consistency of splited files on a networked system. When one user edits the file, when do other users see the edits?
* At first peek this appears to have all of the synchronization issues. Unfortunately the long waits involved in network operations prohibit the use of atomic operations.
UNIX Semantics
* The UNIX file system uses the subsequent semantics:
* Writes to an open file are instantly visible to any other user who has the file open.
* One execution uses a shared location pointer, which is adjusted for all sharing users.
* The file is associated with a single exclusive physical resource, which may wait for some accesses.
Session Semantics
* The Andrew File System, AFS uses the subsequent semantics:
• Writes to an open file are not instantly visible to other users.
• When a file is closed, any modifications made become available only to users who open
the file at a later time.
* According to these semantics, a file can be associated with many ( possibly different ) views. Almost no restraints are imposed on scheduling accesses. No user is waited in reading or writing their personal copy of the file.
* AFS file systems may be accessible by systems about the world. Access control is kept through ( somewhat ) difficult access control lists, which may grant access to the entire world (literally ) or to specifically named users accessing the files from specifically named remote environments.
Immutable-Shared-Files Semantics
Under this system, when a file is declared as divided by its creator, it becomes immutable and the name cannot be re-used for any other resource. Hence it becomes read-only, and distributed access is simple.