Section 10.4. EPCglobal Specification
10.4. EPCglobal SpecificationEPCglobal, Inc., is a joint venture between the UCC and EAN International. The aim of EPCglobal is to establish worldwide standards for designing, implementing, and adopting Electronic Product Code (EPC) and EPCglobal Network (described later). The EPCglobal specification (soon to be deemed a standard) targeted for supply-chain operations is probably the most promising global specification for RFID that can also be applied to a very wide array of applications. A short history of EPCglobal is in order. EPCglobal, Inc., took over the administrative responsibilities of its predecessor Auto-ID Center on November 1, 2003. The research functions of Auto-ID Center were transferred to several worldwide Auto-ID labs. EPCglobal, Inc., maintains a very close relationship with Auto-ID labs to enhance the technology and meet future needs. Auto-ID Center was founded at M.I.T. in October 1999 as a partnership research program sponsored by 100 companies and 5 of the world's leading universities. It was responsible for conceptualizing, creating, and promoting the original specification called the Auto-ID Center specification that involved the EPC technology. Why was the transformation from Auto-ID Center to EPCglobal, Inc., needed? After the EPC technology was sufficiently developed in the research setting, the need of an experienced standards body was felt to commercialize and drive global adoption of the technology. Both EAN and UCC have several years of experience in handling standards, and the combination of these two bodies truly makes one of the most globally capable entities for advancing the EPC and EPCglobal Network. The following section discusses EPCglobal Network, which is the fundamental component of the EPCglobal specification. 10.4.1. EPCglobal NetworkThe EPCglobal Network is a collection of technologies that can provide automatic, real-time identification and intelligent data sharing of an item both within and outside of an enterprise. Although this is geared toward the supply-chain operations of an enterprise, it can be applied in other types of applications (for instance, item tracking and tracing [see Chapter 4, "Application Areas"]), too. Five main technology components make up the EPCglobal Network, as follows:
Thus, the EPCglobal Network "equation" can be summarized as follows: EPCglobal Network = ID System + EPC + Middleware + DS + EPCIS (1.1) In addition, EPCglobal provides a reference architecture for the network. The next subsections discuss these components in detail. These descriptions are followed by a section that explains how these components interact together to form the EPCglobal Network. 10.4.1.1. Electronic Product Code (EPC)The Electronic Product Code (EPC) is a license-plate type identifier that can uniquely identify any item in a supply chain. It is a simple and compact scheme that can generate extremely large quantities of unique identifiers. At the same time, this scheme allows accommodation of legacy codes and standards such as the following:
A company that uses bar codes in its operation today can have a migration path to RFID using EPC. An EPC code can be used to determine various attributes of an item, such as the following:
Two EPCs can be of different sizes. Currently, 64 bit and 96 bit are the most predominantly used EPC tags in practice; 128-bit EPC tags have now started to appear in the marketplace with 256-bit EPC tags in the specification/prototype stage. Note that a 96-bit EPC is sufficient for most supply-chain operations (for reasons stated later). The structure of EPC as prescribed by the EPCglobal specification primarily consists of four parts that corresponds to the preceding attributes:
Figure 10-1 shows these fields of a 96-bit EPC. Figure 10-1. A 96-bit EPC.
An EPC can also incorporate an optional filter value based on which EPCs of tagged objects can be filtered in an efficient manner. Using 96 bits, you can generate a total of 79,228,162,514,264,337,593,543,950,336 (or about 80,000 trillion trillion) unique numbers! Another way of looking at a 96-bit EPC is that it can provide unique identifiers for 268 million companies with each company able to represent up to 16 million object classes and up to 68 billion unique serial numbers for each such object class. Note that an EPC is strictly a unique identifier and nothing else. Therefore, any product-specific information has to reside separately in the enterprise back-end systems. The following subsection discusses a very important concept called EPC Class tags. 10.4.1.1.1. EPC Class TagsEPCglobal has defined the following four classes of EPC RFID tags to provide a range of capabilities at different price points. You should become intimately familiar with this classification because this is one of the core concepts that you might soon be using on a daily basis. Chapter 1, "Technology Overview," explains the terms used here:
The following subsections discuss these classifications in detail. 10.4.1.1.1.1. EPC Class 0/Class 1Both of these tag types are passive tags that can store either 64 bits or 96 bits of EPC data. A Class 0 tag data consists of a unique serial number that has already been written by the manufacturer before this tag is shipped to a customer. Class 0+ and Class 1 are WORM tags that allow data to be written by a customer at the point of use. Class 0 is defined for UHF (900 MHz) whereas Class 1 is defined for both UHF (860930 MHz) and HF (13.56 MHz). All these tag types use backscatter technology for reader-to-tag communication. The tags are beam powered. These are the cheapest tag types available. Currently, Class 0 and Class 1 tags are not interoperable. (That is, a reader that can read a Class 0 tag might not be able to read a Class 1 tag and vice versa.) A UHF Generation 2 tag (often referred to as EPC Gen 2 or simply Gen 2 tag) is a new generation of EPC WORM tags based on the UHF Generation 2 Foundation Protocol that will replace the Class 0 and Class 1 tags. The specification was ratified as an EPC standard by EPCglobal on December 16, 2004. A Gen 2 tag is defined for UHF (860930 MHz) and will consist of a 128-bit RW tag with 96 bits reserved for EPC data and 32 bits for error correction and a kill command. Gen 2 products are expected to appear on the market in the near future. 10.4.1.1.1.2. EPC Class 2This is a passive RW tag that can store an EPC together with user data. The minimum user data capacity of such a tag is 224 bits. This tag uses backscatter technology for reader-to-tag communication. A Class 2 tag is beam powered. These are the next-cheapest tag types after Class 0/Class1. These tag types are still in the prototypical stage. 10.4.1.1.1.3. EPC Class 3This is a RW active tag that has a large user data capacity that is not specified at this time. A Class 3 EPC tag supports on-board processing and I/O capability. This tag uses backscatter technology for reader-to-tag communication and is transmitter powered. These are the next-cheapest tag types after Class 2. Class 3 tags are yet to be produced even for prototypical use. 10.4.1.1.1.4. EPC Class 4This is a RW active tag with a large user data capacity that is yet to be specified. It supports on- board processing and I/O capability. This tag uses transmitter technology for reader-to-tag communication and is battery powered. The minimum read range is 300 feet (about 91 meters). These are the most expensive tag types. Class 4 tags are yet to be produced even for prototypical use. 10.4.1.2. Data-Collection HardwareThe EPCglobal has already released specifications for EPC tags and interface protocols based on which readers and tags can be interoperable from different vendors. For example, a Class 1 EPC tag from one vendor could be read by a Class 1 EPC compatible reader from another vendor. This open nature provides great flexibility and promotes competition among different vendors to bring out superior products at a cheaper cost. 10.4.1.3. Discovery ServicesThis suite of services mediates and provides the access to EPC data. Object Naming Service (ONS) is a component of these services, and it is described in the following section. 10.4.1.3.1. Object Naming Service (ONS)The ONS is a public service that can be used to find related EPCIS servers from where data about a product can be extracted. It provides a mapping mechanism between an EPC and the set of EPCIS instances that contain information about this EPC. (Thus, in essence, ONS is very similar to the DNS service that is used to look up the associated hosts for a particular Internet address.) The ONS service has to perform in real time so that it can quickly handle a very large number of requests (for example, in the trillions per day) reliably. In summary, the ONS is a service for extremely fast and reliable global database lookup. 10.4.1.4. EPCglobal MiddlewareA tag can be read multiple times by the same or different readers at different points in the supply chain. Each such read generates tag data on the reader side and hence on the EPCglobal Network. As a result, a tremendous amount of data is generated on the EPCglobal Network as a result of reading the tags. A substantial portion of this data can be compressed because it might just consist of duplicate reads, reads that can be combined with other reads, and reads that are not significant in terms of business logic, and so on. If this data were stored and transported as is, most storage systems and networks would collapse. To handle this data efficiently, it needs to be sorted, filtered, and processed so that it can be managed in real time. This is the functionality of EPCglobal middleware. In addition to the previously described tasks, it is also responsible for movement of relevant information through the network to EPCIS or other business back-end systems of an enterprise. As a result, the data volume is reduced and data is transmitted selectively in the network, making the use of such data efficient and useful. 10.4.1.5. EPC Information Services (EPCIS)These are gateways hosted by secure servers that contain information about items with EPC numbers in an EPCglobal Network. An EPCIS associates EPC data with business events and information. This is useful for automatically triggering execution of event-based logic. Several EPCIS instances can store the information about a single EPC number. Thus, information for a particular EPC is distributed in nature. Therefore, to assemble particular information about an EPC, data from several EPCIS instances might need to be extracted and merged. An EPCIS can act as a façade to a collection of business back-end systems, such as warehouse management systems (WMS), enterprise resource planning (ERP), and homegrown systems. EPCIS instances of a business should be shared among trading partners, suppliers, and clients to increase collaboration with these parties. Information from EPCIS is extracted in the form of Physical Markup Language (PML), which is described next. 10.4.1.5.1. Physical Markup Language (PML)This is an open XML schema for representing product information as well as communication. Currently, PML can be divided into the following two parts:
The next section discusses how these components work together to form the EPCglobal Network. 10.4.1.6. Tying It All TogetherThe EPC data on the tags is read by the readers. This data is then passed to the middleware for proper management via wired or wireless network. The Discovery Services provide the location information of the EPCIS instance to the middleware. The middleware adds location and event information to the processed data and moves it to the appropriate EPCIS instance for storage and action. Figure 10-2 shows this process. Figure 10-2. An EPCglobal Network schematic.
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