Technical Design Overview | Client/Server Architecture | Network Integration | Dedicated Server | System Security
ERL Client Functionality | Client Platforms | Workstation Requirements | PC-SPIRS ERL Client | WinSPIRS ERL Client | MacSPIRS ERL Client | UNIX-SPIRS ERL Client | Client Software Distribution
ERL Server Functionality | UNIX Versions Supported | Mass Storage Capacity | Simultaneous User Capacity | *Multiple Server Support | Load-Balancing Options | Customer Support
Accessing ERL | ERL Logon | Authorized User Access | Query Protocols | Support for Ethernet or Token Ring | TCP/IP | TCP/IP Addresses | Remote Access | Direct Internet Connection | Modem | Cross-Consortium Access
ERL-Compliant Databases | Media Independence
ERL Administration | Managing User Accounts | Database Administration | Usage Statistics
ERL Systems Comparison | Advantages of Client/Server Architecture | ERL advantages over Mainframe Tape Loading | ERL advantages over CD-ROM and Hard Disk File Servers
The Electronic Reference Library (ERL) is SilverPlatter's solution for providing Wide Area Network (WAN) access to all major databases via TCP/IP. Based on client/server architecture, ERL has two main software components: the ERL clients (retrieval interface), and the ERL server (search engine). Databases mounted on one or more UNIX servers are searchable using SilverPlatter's familiar PC-SPIRS, WinSPIRS, MacSPIRS or UNIX-SPIRS retrieval software on the user's choice of platform: DOS, Windows, Macintosh or UNIX.
End-users can choose retrieval software in their native computing environment, taking full advantage of the power of their equipment and limiting their training needs. ERL does not compromise the performance of the retrieval software. Each SPIRS ERL client retains the search functionality of its stand-alone counterpart, ensuring that it offers retrieval tools geared towards both novice and professional users.
ERL is scaleable, meaning it can support any number of SilverPlatter databases and simultaneous users. A typical, media independent ERL server supports up to 30 simultaneous users and up to 26 SCSI storage devices. SilverPlatter designed ERL to support multiple servers in large, high-access environments. Access to these servers is seamless to the end-user, so you can create as large an electronic library as your resources allow.
ERL enables you to collect, organize, and distribute electronic information across institution-wide or cross- consortium networks, and out to the Internet. SilverPlatter designed ERL as a database networking solution for libraries, so it is manageable by a librarian, from his or her workstation, without requiring system expertise. You can manage user accounts, database administration, security and usage statistics through a front end program called ERLADMIN.
Client/Server Architecture
ERL uses client/server architecture to create an efficient, secure, and low-cost solution for small and large networks. Client/server architecture is the basis for most open systems built today. It cleanly encapsulates the task of database searching for end-users, without compromising search sophistication. Client/server architecture establishes the framework for a unified window onto all information sources through the standardization of database functionality and content, enabling multi-vendor integration of electronic information.
Network Integration
SilverPlatter constructed ERL from standard components, so it integrates into a typical campus environment. The ERL server software runs under UNIX. Retrieval clients are available for DOS, Windows, Macintosh and UNIX. These clients communicate with the ERL server using TCP/IP, a popular protocol for campus network computing. SilverPlatter's ERL server (for SCO UNIX) and PC clients also support Novell Netware's IPX protocol, and will fit into a variety of networks. Client/server efficiency means ERL clients are compatible with a variety of LAN and WAN technologies, from simple serial connections and long- distance phone connections, to Token Ring, Ethernet, and fiber optics; any communications technology that supports TCP/IP or IPX. (Figure 1)
Dedicated Server
ERL treats the server software, databases, operating system, and hardware as a dedicated, self-contained unit. The only access to the contents of the server is through the Data eXchange Protocol (DXP) query and response protocol.
Your users do not log into the UNIX server nor do they have access to the server's prompt. The ERL server only understands the DXP query and response protocol thus securing your information and ensuring that the server locks out unauthorized users. ERL is designed to offer high performance and reliability as the server is dedicated to running ERL, and therefore performs fewer tasks. Furthermore, there are no other user applications running on the server that could cause system crashes, or compete for computing power.
System Security
ERL's dedicated server design and account administration feature limits access to your authorized users. Installed databases contain a write-protected, site-specific electronic license specifying the terms of the database subscription.
SilverPlatter designed the ERL client software to function as a search retrieval interface. It presents search functionality to the user, communicates search queries to the ERL server, and presents the results of the search on the user's workstation. Actual searching takes place on the ERL server, and it communicates the results back to the client for presentation on screen.
This client/server design enables users to choose their desired client (interface) such as WinSPIRS, MacSPIRS, PC-SPIRS or UNIX-SPIRS, regardless of the server platform. SilverPlatter has designed ERL retrieval clients to take advantage of the style, functionality and conventions of each platform. For example, WinSPIRS takes advantage of pull-down menus, dialog boxes, and other features available in a Windows environment.
The clients available for ERL are PC-SPIRS for DOS users, WinSPIRS for Windows users, MacSPIRS for Macintosh users and UNIX-SPIRS supporting terminal users.
PC-SPIRS ERL Client
PC-SPIRS is the world's most widely distributed search and retrieval software for DOS. It is a powerful retrieval system that operates on IBM PC and compatible computers.
WinSPIRS ERL Client
For machines equipped to handle Microsoft Windows, WinSPIRS provides a one-screen view of the search terms, search and retrieved records so that users can easily see the kinds of searches that are resulting from their queries. WinSPIRS also provides Automatic Subject Lookup which can offer alternative terms from the database's controlled vocabulary to narrow or expand searches.
MacSPIRS ERL Client
SPIRS for the Macintosh environment provides access to information with the user-friendly Macintosh interface. MacSPIRS features pull-down menus, Macintosh shortcuts, and more.
UNIX-SPIRS ERL Client
SilverPlatter's UNIX-SPIRS client offers support for heterogeneous desktop environments and remote access. Through the standard Telnet protocol, diverse desktops are able to use terminal emulation to connect to the UNIX host running the client. The UNIX-SPIRS client works on Sun Solaris. Users with workstations that do not have a direct TCP/IP connection but support Telnet, are able to Telnet to a Sun Solaris host, which will run the client on behalf of the user workstation.
Client Workstation Requirements
The minimum hardware and software requirements for ERL clients can be found in the SilverPlatter Erl Hardware Requirements document.
Client Software Distribution
Administrators can install the client software on a networked file server, distribute it to each user for installation on their workstation, or can combine the two options.
Installing the client on a file server allows all search stations to share the same copy of the client software. This also eases administration by keeping all users current with the most recent version of the client software.
To distribute the client software, the administrator will need to transfer the appropriate client files from the ERL server to the client workstation. There are three methods of distribution:
While there may be some additional effort involved in distributing the client to them, end-users will be able to customize their client software with defaults specific to their searching needs and habits. The client software will also initialize faster if installed on the user's workstation. This is particularly important for dial-up users, or users of other low-speed networks.
The installation process is identical to the process for installing a stand-alone version of SPIRS. So once distributed, users can install the SPIRS ERL client software with ease.
The ERL server performs three main functions: it acts as the database search and retrieval engine; it is the utility for installing SilverPlatter databases in ERL; and it controls user access to databases and the ERL system. ERL integrates with any TCP/IP or IPX network. SilverPlatter delivers pre-indexed CD-ROM databases, facilitating updating while the system is in use. The server, running under UNIX, is capable of performing simultaneous searches for multiple users.
The first release of ERL supports a SCO UNIX server on an Intel platform. This offers performance which is comparable to some RISC platforms, yet the price is below the cost of many RISC boxes. A typical ERL server for SCO UNIX would be a 486, 50MHz workstation with a minimum of 32 MB RAM and mass storage devices for the ERL databases to be supported.
The next ERL server platform will run under Sun Solaris. Over time, SilverPlatter will provide IBM AIX, DEC OSF-1, and Hewlett Packard HP-UX ERL server software platforms.
For more information on server hardware requirements, please refer to the SCO UNIX ERL Integrators Guide or contact SilverPlatter or your local distributor.
The only limit to the number of databases that an ERL server can hold is the mass storage capacity of the selected server. This varies by platform. A typical Intel ERL server configuration (for SCO UNIX) has a capacity to hold up to 26 mass storage devices on a single server. This would, for example, support three controllers managing an array of 3.0 Gigabyte (GB) hard disks with over 78 GB of hard disk space--enough room for 112 CD-ROM discs. Support for multiple servers removes all limits to the size of the database collection.
The system for the SCO UNIX ERL server is capable of supporting 30 simultaneous users, each user requiring 2 MB of RAM on the server. The addition of more servers will increase the system capacity. Because different platforms may have faster processor power and higher limitations for maximum RAM capacity, the number of simultaneous users on a single server may vary over different server platforms. Future releases of ERL will support alternative versions of UNIX and will provide the capacity for a greater number of simultaneous users per server.
Sites may install many ERL servers in distributed locations. Clients can currently access up to four servers by including the TCP/IP addresses of the servers in the client software configuration file. The fact that there are multiple servers is transparent to the end-user. The client presents a single scrollable list of all the databases from each of the servers available to that user.
To facilitate decentralized autonomy, ERL servers can be in multiple locations. Each library site can then manage their own collection. Libraries can choose to have different types of ERL servers if their preferences for hardware differ.
Servers, and the number of databases they control, can be mixed in ratios that satisfy the usage requirements of the particular site. Typically, a server will host many databases, and, if the simultaneous user limit or mass storage capacity is not exceeded, the site may choose to add more databases to that server. If a server is overloaded, the site may choose to add additional servers to host additional copies of the most heavily used databases. For example, a site may configure two PsycLIT servers, one ERIC server, and a fourth server with sociofile, EconLit, and PAIS International. ERL will present users with a list of the databases to which they have authorized access, regardless of the server to which the databases are attached.
SilverPlatter can diagnose ERL server problems over the Internet and encourages ERL sites not on the Internet to equip their servers with remote dial-in capability.
On starting the ERL client, a user prompt appears requesting a user name and a password. Upon completion of logon, the user's screen will display a menu of all databases available to that individual user. In doing this, ERL organizes and presents the information available to the users.
Only authorized users can access the ERL system. ERL is secured by maintaining a list of authorized users that is separate from the UNIX passwords identified to the server's operating system. This provides an extra level of security and allows consistency of access privileges in a multi-server environment.
You can import user accounts from an existing file, or add them manually. ERL includes a utility, ERLADMIN, for managing access to the databases on an ERL server.
Anonymous logon, or TCP/IP address checking, provides a method for allowing authorized access to users without assigning individual user accounts. As an example, this is an appropriate configuration for public access workstations in the library.
The Data eXchange Protocol (DXP) is ERL's native protocol for client/server interaction. SilverPlatter designed DXP with bibliographic and full-text retrieval in mind. With DXP, the ERL server benefits from client/server architecture, without compromising the functionality found in SilverPlatter's stand-alone retrieval systems. Today, the DXP specifies retrieval functionality which includes: Boolean searching, thesauri, Hot Links, and multi-database searching. Future releases of the DXP will specify increasingly sophisticated retrieval tools such as meta-thesauri.
Organizations with development capabilities can develop their own ERL clients by writing them to the DXP. This means that the other vendors' clients written to the DXP can take advantage of the functionality that DXP specifies to access ERL compliant databases.
In ERL, the DXP co-exists with various industry standards, such as those emerging for libraries (Z39.50), hospitals (HL-7), and corporations (SQL). For example, in the library industry, clients written to Z39.50 can access all ERL compliant databases through a gateway. SilverPlatter has programs to share our technology with vendors who want to develop gateways from their clients to ERL compliant databases.
ERL is compatible with almost any network technology that supports TCP/IP. TCP/IP applies to a variety of network hardware technologies, including Ethernet, Token Ring, Localtalk, dial-up lines, and serial connections.
The following rules apply:
Workstations must have a TCP/IP address to run an ERL client. Those users without a TCP/IP address have the option of remote dial-in access.
There are a number of ways to access ERL remotely. Almost any strategy is sufficient for ERL, as long as the client and server can communicate via TCP/IP.
If the server and the remote user have direct Internet access and have implemented proper security procedures, the remote user can access the server by indicating the name or address of the server to the client. This client must be installed locally and will have the same functionality as any other on-campus client.
If the remote user does not have a machine compatible with an ERL client, a future option will be to Telnet over the Internet to a UNIX host on the network running the UNIX-SPIRS ERL client.
There are four different dial-in methods:
ERL's client/server design offers efficient use of network bandwidth for large, multi- institution access. Possible solutions for providing cross-consortium access to ERL include taking advantage of either the Internet or a private WAN connecting a specific consortium. Sites may offer a variety of access paths to the same ERL, such as a direct network connection or any dial-in strategy.
Each ERL administrator controls the security for multiple server access over the Internet. Through the use of either user names and passwords or TCP/IP address ranges, a server is configured to indicate the machines and/or users who have permission to use one or more of the databases located on that server. Authorized users are presented with a single list of available databases, which may reside on a number of ERL servers.
Today 200 SilverPlatter databases are ERL compliant. Over the next year SilverPlatter will establish a program to allow third parties to publish their own ERL compliant databases. For example, a university could publish small files of local interest for access by ERL clients.
Furthermore, because the ERL security allows access to be restricted to a site, it is now possible for SilverPlatter to publish databases currently only available for tape lease through information providers. SilverPlatter therefore anticipates that we will be publishing major databases previously unavailable.
These two programs and SilverPlatter's existing database launch program will ensure a growth in titles.
ERL is media independent so it accommodates databases in either CD-ROM or hard disk format. With ERL, you can copy databases to hard disk and create hybrid CD-ROM/hard disk solutions that make optimum use of available hardware. SilverPlatter offers four database installation levels with the DBINSTALL program, ranging from full CD-ROM to full hard disk. The server reports how much hard disk space is being utilized by each database, so that you can track hard disk consumption.
The ERL administrative (ERLADMIN) software is a DOS application that runs on the administrator's workstation. Therefore, you do not have to be a systems expert to control user access to your database network. You can manage databases on more than one ERL server from your workstation by logging into the other servers as the administrator. The ERLADMIN software helps manage a number of functions including User Accounts, Database Administration, Usage Statistics, and Accounting.
As an administrator, you establish names of either individuals or groups of users. You enter these names manually or copy them through an automated import procedure from an existing comma delimited text file. You can set a simultaneous logon limit per user name and establish each user name with a specific expiration date.
Anonymous logon offers large institutions an alternative for specifying individual user names by using valid TCP/IP address ranges to identify authorized users. Users logon to the system under the user name "anonymous" and the server verifies that their workstation has a valid, authorized TCP/IP address. You can employ user name authorization and anonymous logon in combination. Local users may have anonymous logon authorization but users who are remote from the network, outside the campus' TCP/IP address range, require user name and password in order to access the system.
As you install databases on ERL, you can establish which user accounts have searching privileges on each database. For ease of administration, database authorization files can be copied from one database to another. At any time you can view or print a report of all databases identified on ERL, as well as view the list of current users for each one.
ERL automatically maintains statistics on database usage and user account access to the ERL system. You can export these statistics in DOS ASCII format and import them into spreadsheet or database analysis packages. ERL maintains statistics on a daily basis, compiling them into a monthly report over 31 days. You can also export statistics for any period of time.
Here are some examples of information you can collect in reports:
This section compares ERL to the technologies typically used to provide campus-wide access today, including mainframe tape loading, traditional CD-ROM, and hard disk file servers.
Administrator - The individual(s) responsible for the day-to-day operation of the ERL server. The administrator's duty typically includes loading and updating software, loading and updating databases, authorizing access to databases, etc.
Backbone - In a campus, the main network cable to which all departmental LANs are connected. Communications traffic between computers on different departmental LANs travels over the backbone.
Bandwidth - The capacity of a physical segment of a network expressed as the maximum amount of data that can be passed over the physical segment each second. This is often expressed as a theoretical maximum. Ethernet's theoretical bandwidth is 10 Mb/s (millions of bits per second) or approximately 125,000 bytes per second.
Client - The retrieval interface with which the end user interacts. The client is responsible for accepting queries from the user, formatting them according to the DXP specification, and then sending them to the server. The client is also responsible for receiving the server's response to the query, and for formatting retrieved records for display, print or download. The client software must be compatible with the end user's computer.
Client/Server Architecture - A computing strategy that divides a software problem into two pieces, a consumer and a producer, with each piece insulating the other from the details of its operation. In ERL, the software problem of database retrieval is divided into two pieces: 1) search and retrieve (the server), and 2) query formulation and results display (the client). The client and server communicate using an agreed-upon messaging strategy called a protocol.
Data eXchange Protocol (DXP) - The messaging strategy (rules and formats), invented by SilverPlatter, that is used by ERL servers and clients. DXP specifies the rules that the client software uses to express a search query in a format understood by all DXP-compatible servers which is independent of the client environment. DXP also specifies the rules that the server software uses to express the format of the results of the request so that any DXP-compatible clients may process the response.
Ethernet - A set of standard cabling and network interface hardware technologies used to connect computers into a LAN.
Fiber Optic - A high-speed network cabling technology that transmits data as pulses of light (as opposed to pulses of electricity).
Integrator - The individual(s) responsible for combining the server hardware components (and sometimes the network hardware as well) in preparation for its operation as an ERL server.
IPX - Novell, Inc.'s Internetworked Packet eXchange protocol. IPX is the native layer 3 (network layer) protocol used by Netware LANs. Layers of software above IPX can use IPX to deliver messages for a variety of LAN applications such as e-mail, databases, file services, LAN printing, etc.
LAN - Local Area Network. Typically defined as a set of computer devices connected by high-speed cabling and network interface technologies. These high-speed technologies have modest distance limitations which limit the LAN (hence the term "local area") to a set of computers within a few miles of each other.
MacTCP - The software driver for the Macintosh operating system that implements the TCP/IP protocols. These protocols provide core transmission services used by third-party applications such as e- mail, remote logon, file transfer, and database access.
Packet Drivers - A software interface that allows client programs to use a standard approach for communicating with the network hardware of a PC workstation. Packet drivers insulate client software from the differences that exist between network hardware manufactured by different vendors. Packet drivers for most network interface boards are available free from sources on the Internet, and elsewhere.
Server - The computer program, and machine that is responsible for satisfying client search requests. Sometimes called an application server to distinguish an ERL server's role from a LAN file server. The ERL server is a UNIX machine with mass storage devices (hard disks or CD-ROM drives) on which SilverPlatter databases are stored.
TCP/IP - Transmission Control Protocol/ Internet Protocol, the layer 4 (transport) and layer 3 (network) protocols used by the Internet, and many other WANs and LANs. TCP/IP handles reliable message transfer duties for a variety of network applications such as e-mail, file transfer, and remote logon.
Telnet - A protocol allowing intelligent computers to emulate terminals and connect to hosts over networks using TCP/IP. Telnet is a standard capability for all implementations of TCP/IP.
UNIX-SPIRS Client - An ERL client compatible with UNIX terminals and the Telnet protocol.
WAN - Wide Area Network. A set of computers which can communicate over great distances. WANs use lower speed network technologies than LANs, and are compatible with long-distance networks such as the public telephone system.
WinSock - An Application Programming Interface (API) specification which defines a standard interface between a Microsoft Windows application, and a TCP/IP protocol stack.
Z39.50 - Information Retrieval Protocol for Library Applications. An American National (ANSI) Standard (or in some cases, its international version ISO 10162/10163 SR) for client/server database retrieval. Version 2 of Z39.50 was published in 1992. Version 3 is currently being defined.
For more information about ERL contact info@burioni.it