Free Traceability Management using RFID and Topic Maps

Abstract

The CRDO (Consejo Regulador de la Denominación de Origen "Jamón de Teruel" - Governing Board of the Protected Designation of Origin "Ham from Teruel") is involved in the development of a system that guarantees the traceability of the pig's legs. This initiative is innovative since there is no other Governing Board which has such a system to respond to unforeseen circumstances occurred at the slaughterhouse unit. To accomplish the requirements, three different strategies have been followed: (i) RadioFrequency Identification (RFID) technology, which uses a wireless link to transfer data in a fast and easy way - just placing the tag within the communication range of the reader - between read/write access points strategically placed in the slaughter chain and tags attached to every pig's leg, (ii) the security of the traceability system, that provides evidence that all the controls in a production process have been activated. This enables the client to quickly verify that all the products have correctly passed through the production cycle with the guarantee of trust provided under the responsibility of the signer, and (iii) a free documentary management system (DMS), which is necessary to correctly manage the information collected during the slaughtering process. This paper is focused on the third strategy. To develop the documentary management system, we use the ISO 13250 which defines the Topic Maps paradigm, and its XTM specification. The combination of both technologies (RFID and XTM) in the traceability system offers several advantages to manage the online information in real-time. [PUBLICATION ABSTRACT]

Headnote

Abstract: The CRDO (Consejo Regulador de la Denominación de Origen "Jamón de Teruel" - Governing Board of the Protected Designation of Origin "Ham from Teruel") is involved in the development of a system that guarantees the traceability of the pig's legs. This initiative is innovative since there is no other Governing Board which has such a system to respond to unforeseen circumstances occurred at the slaughterhouse unit. To accomplish the requirements, three different strategies have been followed: (i) RadioFrequency Identification (RFID) technology, which uses a wireless link to transfer data in a fast and easy way - just placing the tag within the communication range of the reader - between read/write access points strategically placed in the slaughter chain and tags attached to every pig's leg, (ii) the security of the traceability system, that provides evidence that all the controls in a production process have been activated. This enables the client to quickly verify that all the products have correctly passed through the production cycle with the guarantee of trust provided under the responsibility of the signer, and (iii) a free documentary management system (DMS), which is necessary to correctly manage the information collected during the slaughtering process. This paper is focused on the third strategy. To develop the documentary management system, we use the ISO 13250 which defines the Topic Maps paradigm, and its XTM specification. The combination of both technologies (RFID and XTM) in the traceability system offers several advantages to manage the online information in real-time.

Keywords: Traceability, RFID, Topic Maps, Documentary Management System

1. Introduction

Traceability has been defined as the ability to trace the history, application or location of that which is under consideration (ISO 2000), or as the ability of the retrieval of the history and use or location of an article or an activity through the registered identification (ISO 1994). Traceability is a growing business, particular for food and drug products. Traceability of drugs is primarily focused on ensuring that fake drugs are kept out of the system. In the case of food, the primary aim is the ability to track a food quality problem (such an outbreak of salmonella or excess antibiotics in meat). Traceability systems are mandatory in the European Union since January 1, 2005 for all activities related to food production and distribution. The aim is to guarantee the quality, safety and security. Every element that takes part in the food chain must be perfectly identified and its history must be perfectly known at all the stages (EufoodTrace 2005). Moreover, traceability is an important aspect of marketing and brand positioning.

Traceability is one of the main applications of the RFID technology that uses a wireless link to transfer data between a reader and a transponder by means of a modulated radio frequency carrier signal. Each of these transponders or tags contains a unique identification number that will unambiguously identify any element to which is attached. All the information related to this item will be saved in a database associated to this number. Any new information can be physically stored in the traced element in the memory of the tag, and data can also be retrieved at any point where a RFID reader is placed. This process of reading and writing information does not require any contact or perfect alignment between tag and reader; so, just placing the tag within the communication range, the new information can be read or written in a fast and easy way.

The RFID identification of pigs is not mandatory in the EU as in the case of goats, sheep (EC 2004) or cows (EC 2000), but several examples of RFID-based traceability systems applied to the production of pig by-products can be found in the case of living animals (Babot 2004) and (Chiesa 2003), and also in the production of meat and ham (De la Fuente 2005), and (Hernández 2001). In this paper, we concentrate on the legs of the pigs alone. Hence, the traceability system only controls the parameters of the slaughter process to guarantee that the ham produced deserves the quality brand "Jamón de Teruel". The process should be completed including the previous information (birth and feeding data) and the information related to both the consequent salting and drying processes.

The ISO standard 13250:2003 (ISO 2003), known as Topic Maps, is an instrument used to represent the conceptual structure of the information contained in an online information resource. The biggest contribution of such structures, which comprises the visual aspects, semantic networks, and text, to knowledge representation lies in the fact that, when combined, they are much more effective than when considered separately (Tramullas 2006). In 2000, Topic Maps were defined using an XML syntax (XTM 2000) known as XTM (XML for Topic Maps). This version was updated in 2006.

The preliminary design of the traceability system to be developed in the slaughterhouse of the company Pelbor SA in Calamocha (Spain) was outlined in a previous work (López 2009). Nevertheless, the final scenario of the practical implementation of the system has changed due to new requirements. Thus, the slaughterhouse where the traceability system must be definitely implemented is located in La Mata de Los Olmos, province of Teruel, Spain. This slaughterhouse also belongs to the company Pelbor SA, a company which is associated with the "Consejo Regulador de la Denominación de Origen" (CRDO).

The most important technical problems found in the implementation of the traceability system described in this paper made that RFID tags were lost or damaged. These problems were caused by the adverse environmental conditions found at the slaughterhouse (high degree of humidity, low temperature, presence of metallic surfaces, etc.). Moreover, the novelty of the proposal and the lack of references on the topic, challenged the successful implementation of the RFID-XTM based design.

References on this topic are still non-numerous. Two relatively similar experiences carried out in China have been recently reported. In (Zhu 2008), a general overview of a traceability information system focused on pork meat can be found. (Zhao 2009) proposed a RFID-enabled traceability system for pork supply chain. The study emphasized the relevance and the feasibility of the RFIDbased system as a tool to improve the quality and the safety during the entire process of meat production, but it did not provide a description of how the technical problems were solved. In addition, none of these works used Topic Maps in their solution.

The rest of the paper is organized as follows: Section 2 presents the objectives of the reported project. Section 3 shows the basic assumptions and the proposed framework to manage the information traceability system. Section 4 presents the Documentary Information System characteristics and why we used Topic Maps in our solution. Section 5 deals with the evaluation made until now. Finally, Section 6 describes the main conclusions, and the future steps and recommendations for the slaughterhouse.

2. Objectives

The main goal of the project reported in this paper is to automate the collection of relevant information that the CRDO requires, guaranteeing the quality of the worldwide known dry-cured ham. This general aim can be divided into six more specific objectives. Hence, the application designed and implemented must:

* Collect at the entrance of the pigs into the slaughterhouse the information about their breed, farm of origin, and feeding. The animals, whose meat is sold under the CRDO quality brand, must fulfil a number of specifications from the moment they are born until their entrance into the slaughterhouse (Orden 1993).

* Add all the information required by the CRDO at the moment when data are generated at the slaughterhouse. Hence, the system provides the resources to guarantee the quality of the products identified by the Designation of Origin "Jamón de Teruel" (Orden 1993).

* Process the data captured via RFID by an ad-hoc interpreter algorithm in real-time. The application is able to add semantics to the basic information captured and placed in the context (ISO 2003)]. Moreover, it should store this information in an extended denormalized database under the premise that a RFID tag is uniquely associated to every pig's leg.

* Store this information in three different information repositories, namely, the local database of the information management system, the main database of the CRDO, and a RFID tag uniquely associated to every pig's leg.

* Guarantee the authenticity and integrity of the data saved in the tag. A security system based on aggregate signatures has been developed in order to carry out this task (Azuara 2008).

* Quantify the number of hams rejected throughout the process (including information about why a pig's leg does not meet the CRDO requirements). The RFID tags associated to the rejected hams must be written so as to avoid their trade under the Designation of Origin "Jamón de Teruel".

The work presented in this paper corresponds to the design and implementation of the traceability process carried out in the slaughterhouse. Once the pig's legs are taken apart from the carcass in the slaughterhouse, they suffer a drying process under specific conditions of temperature, humidity and salt content that takes place in a different location, whose management is out of the scope of the current project.

3. Description of the traceability system

This section shows the background and the CRDO requirements to take into account, and details the steps taken to develop the proposed framework for the real-time information management system using the facilities of the slaughterhouse of the company Pelbor SA placed in La Mata de Los Olmos, Teruel, Spain. Now, we describe the traceability system in terms of where, how and what the information is collected.

3.1 General overview of the slaughtering chain

Pelbor SA is associated with the CRDO "Jamón de Teruel". For this reason, there is always an employee belonging to the CRDO controlling the slaughtering process. This person is named "the inspector" and he is the one in charge of the traceability system.

Figure 1 shows the different steps followed by the pork meat throughout the slaughtering process, from the arrival of the pigs at the yards until the delivery of the pig's legs towards the drying places.

3.2 Scenario, hardware, and information to be collected

Four workstations are going to be deployed in the slaughterhouse: The first one (PC1) at the reception office, the second one (PC2) at the inspector's checkpoint, the third one (PC3) at the quartering room, and the last one (PC4) at the exit of the building (at the point where the pig's legs are delivered). These are the points where the information is collected, and all of them must be connected to the internal communication network. To guarantee the traceability process, some of this information is going to be attached to the pig's legs by means of a RFID tag. This tag, whose characteristics are going to be detailed below, is going to be read/written with RFID readers connected to PCs 2, 3 and 4. Two scales, one connected to the PC2 and the other connected to PC3 at the quartering chamber, complete the necessary hardware.

3.2.1 PC1: The reception office.

When each one of the batches arrives to the slaughterhouse, the following information is collected at PC1:

* Feeding farm of origin.

* Number of animals.

* Number of the yard where the animals have been enclosed.

* Sanitary guide number.

* If the batch has been breaded following the requirement of the CRDO.

* Scheduled slaughtering date and order.

This information is stored in the local database.

The inspector selects which batch is being slaughtered at that moment. He must confirm at the yards, that the batch information is correct. Every batch is uniquely identified by a batch number. Afterwards, when the inspector is working at his checkpoint he already knows how many pigs are going to be slaughtered, from which farms they came from and at which moment of the slaughtering day. The number of animals corresponding to every batch is used as a counter reference by the application to detect possible errors.

3.2.2 PC2: The inspector's checkpoint.

The current traceability system states that at this stage of the slaughtering chain, the inspector examines both back legs from the animal and collects the following information that will determine if the pig's legs meet the CRDO's requirements:

* Weight of every animal. The value must be above 86 Kg. This value is automatically stored from a scale connected to the PC.

* Fat thickness. The value must be within a range from 4 to 7 cm. So far, the inspector must estimate if this requirement is fulfilled just by visual inspection.

* Correct genre: castrated males or females not on heat.

* Lack of bruises, breakages or tumors in the meat.

If the inspector proves that the animal passes all these conditions, he marks it, using ink suitable for food applications, with a specific number composed of ten digits:

* Digit 1: To identify the slaughterhouse.

* Digits 2-3: Week of slaughtering.

* Digits 4-6: To identify the feeding farm.

* Digits 7-10: Ordering (rol) number. This number uniquely identifies the animal among all the pigs coming from the same breeding farm and slaughtered in the same week.

This number indicates that the pig's leg meets the CRDO's requirements, so far.

Figure 2 shows the flowchart of the developed application used by the inspector. When the animal, divided into two parts, arrives to this point, the following actions will take place:

* The scale weights the pig and sends this value to the computer. If the weight is out of the valid range, the application will not generate a new tag.

* The inspector, using the touch screen, indicates if the rest of requirements are met. If not, the tag will not be generated. All the rejection information is stored in the database.

* The RFID printer sends to the computer the identification number of the two tags that are going to be written with the collected information. Thus, every piece is identified in a unique way in the database.

* The program calculates the ordering (rol) number.

* The program generates the aggregate signature from the dates collected and the inspector's username.

* The RFID reader creates two identical tags (one per each leg). The information stored is:

* Feeding farm identification number.

1. Slaughterhouse identification number.

2. Slaughtering week.

3. Rol number.

4. Weight of the animal.

5. Aggregate signature.

This information is also stored in the database together with the identification numbers of the tags. The tag is generated and attached at this point because the previous scalding and peeling steps could destroy this element. Moreover, only the pieces of meat that have passed the watcher's inspection are still candidates to achieve the quality mark.

3.2.3 PC3: Quartering room.

Once taken away from the rest of the pig, each leg identified with a RFID tag is checked individually at a first location in the quartering chamber in order to detect the presence of previously unnoticed defects, such as bruises, tumors or breakages that can make the ham to be rejected. This information is added to the database through PC3 by means of a RFID reader that takes the following steps:

* Reads the tag identification number and sends it to the PC.

* Writes the new information, including a reject value, if this condition is met.

Afterwards, the leg is weighed again. This weight is available at the PC3 connected to the scale. With this new information, the application decides if the ham is still valid for the CRDO (must be above 11.6 Kg.) If not, a message is sent demanding that this piece must follow a different path. The legs that have met all the CRDO requirements are placed in cages. Every cage is associated with one drying place. A second RFID reader connected to PC3 updates the tag and the database with the new information: the leg's weight and its destination. Inside this room, two RFID terminals are needed because the two CRDO's conditions are checked at different positions. In this case, the reading and writing operations are going to be made at a very close distance since each piece is directly handled. Readers Skye Module M2 have been selected. The PC3 at the quartering room will also receive the information of the leg weight directly from a scale. In addition, every piece is assigned to a drying place where the ham will continue its maturation process.

From the new data and the identity of the person in charge, a new aggregate signature is calculated and written in the memory of the tag replacing the previous one. All this information is also sent to the database.

3.2.4 PC4: Exit.

The RFID reader connected to the PC4 sends the information about the exit date to the tag. Since 66 hams can be hold at every cage, it is very difficult to read all the tags and write the new data in them. So, every cage is identified by a unique RFID tag that is going to be read at the exit moment. This information is attached to every tag UID only in the database.

Table I shows the data saved in each tag after leaving the slaughterhouse. Every farm, abattoir and drying place associated to the DO "Jamón de Teruel" is identified by an internal number consisting of three decimal digits.

4. Characteristics of the Documentary Information System

All the information collected in the slaughterhouse is stored in the local database; part of this information is partially stored in the RFID tags' memory, and must also be sent to the CRDO's database. This communication process is designed to be done via TCP/IP protocol in two ways: (i) on demand, and (ii) automatically at the end of every working day.

At the same time, there is information required by the local database that must be updated from the one placed in the CRDO's offices. For example, the number of farms associated to this institution can increase o decrease or just change their name. So the communication between databases must be bidirectional. The update process can also be done on demand, or automatically once a week.

In order to add value to the stored data, we used Topic Maps to improve the slaughterhouse Information System, since they were created to support high-level indexing of sets of information resources to ease the retrieval information process. The semantic expressivity of Topic Maps is similar to that of the Resource Description Framework (RDF), but the major differences are that Topic Maps: (i) provide a higher level of semantic abstraction, while RDF only provides a template of two arguments linked by one relationship), and (ii) allow n-ary relationships (hypergraphs) between any number of nodes, while RDF is limited to triplets. To the best of our knowledge, this methodology has not been previously proposed either in such environments, nor combined with traceability systems.

In our proposal, semantic information is added in an extra layer (see Figure 3) making use of Topic Maps (XTM). The result is not only a denormalization process of a database but also implies an extension. Figure 4 shows the new database extension based on Topic Maps.

This new approach has the following advantages:

* To enable information resources description to be extended in real-time without having to modify its original design.

* To enhance the performance. The relationships between stored objects will be more flexible and the data will be enriched.

* XTM allows us to extract knowledge from the stored data in a more efficient way and to ease the retrieval process. The new design also allows search processes to be less restrictive since we have at our disposal both recovery models, the relational one with binary associations, and the Topic Maps-based with n-arity associations. The current CRDO database makes use of a RDBMS (Relational Database Management System) with textual information, so the recovery model needed is Boolean and data-centered, its main feature is the consideration of relevance that is purely binary. With our proposal, the recovery model is additive. The search can be topiccentered and let us to design a more complete bot, without the need to execute a sequential search. The aim is to have a more efficient retrieval information process and to have the opportunity to provide online information to the farms through wireless communications.

5. Evaluation

One of the key technological challenges to be solved in our traceability system is the selection of the tag material and positioning method. The process must be fast because of the speed of the slaughtering chain. The tag cannot affect the quality of the ham. The presence of a high humidity concentration, recommends the use of the HF band, 13.56 MHz, for the RFID elements.

In order to initialize the tags that are going to trace the items during the whole process, an RFID printer has been chosen. The Avery Denninson Monarch 9855 HF printer writes and reads every tag placed at a very close fixed position. In this way, problems related to interferences or insufficient communication range, are solved. Moreover, the previous visual information used by the traceability system (rol number) can be printed on the tag surface.

Tests have been carried out in real conditions with adhesive tags directly fixed on the pig's leg. The adhesive material must be suitable for being used with meat products. The adhesive used was the SD2800 in compliance with the Regulation (EC 2004). The peeling tool available with the AD Monarch 9855 HF eases the process. The high temperature of the meat at this point and the posterior washing processes gave as a result that more of the 50% of the tags fell down.

At this moment, we are evaluating the time necessary to attach the RFID transponders by means of bridles and fasteners. Chips NPX I-code SLI with a memory size of 1024 bits - large enough for the planned data size - are being used. The speed of the slaughtering chain is 200 animals per hour. Then, so as not to slow down the activity, two tags must be recorded, printed and attached every 20 seconds. In this period of time, the inspector must also inspect the meat and mark it with the rol number.

Our group has developed an application that writes on RFID tags the birth information. Sharing the same database, this application is able to communicate with the program developed for the HF readers, so a PC connected to a low frequency (LF) reader and a high frequency (HF) reader, will transfer the birth information to the HF tag. Our LF system is able to read/write tags at a distance up to 1 meter. We use a RI-K2A-001A module of Texas Instrument with the radiofrequency module S2000 High performance and a Gesant antenna of the same brand. The system is completed with an autotunning element designed by Rumitag.

The success of the prototype performance will extend the use of the RFID technology in other steps of the ham production. A complete traceability system should begin with the animal's birth. Currently, the information of the birth week and the birth farm, which could be different from the breeding farm, is marked on the animal's ear using ink. The CRDO is interested in storing also this information in the tag attached to each pig's leg, but it would require reading the pig's ear at the inspector's checkpoint. The speed of the slaughtering chain does not make possible this action, but the collection of this information could be also automated if it was previously stored in an RFID tag. Living animals are uniquely identified by means of RFID elements working in the range of low frequency, LF, centered at 134.5 KHz. RFID chips are being currently used in pets and are compulsory in the case of sheep, goats and cows (Regulation 2000). RFID ear tags are used in the case of cows and RFID bolus for goats and sheep. The problem of attaching and recovering RFID tags in pigs has not been solved. Solutions like crystal capsules inserted to the hoof or between teats have been proposed (Chiesa 2003).

6. Conclusions

The design and implementation of a RFID-based traceability system working in a slaughterhouse has been described in this paper. The implementation of the designed strategy involves three different research topics: RFID technology, information management, and data security. The steps followed by our multidisciplinary research team were: (i) a preliminary design of the system; (ii) experiments and simulation of the system in the laboratory; (iii) experiments and measurements in the definitive scenario (slaughterhouse); (iv) a redesign of the final implementation on the basis of the results obtained during the previous research, and finally (v) an implementation of the traceability system in the slaughterhouse.

Apart from the common requirements associated to every food chain, the strict quality CRDO's requirements regarding the "Jamón de Teruel" have been met. The internal regulations of this institution determined which parameters had to be traced. The adverse environmental conditions of the slaughterhouse, and the economic restrictions associated to a high-scale production also severely conditioned the design.

Thanks to the integration of XTM in the information management process, some improvements are provided: (i) to supply future navigation tools, (ii) to improve the design of novel interfaces for the inspector, the person who keeps an eye on the ham manufacture process, (iii) to design a recommendation system that meets each user needs, and (iv) to have an external tag mechanism. The combination of both technologies (XTM and RFID) allows to use low capacity tags without renouncing to have a complete description of the information resource, nor altering its original format, and the information recovery process will be improved.

With the developed system we put at the CRDO's disposal, a powerful system which allows to develop different search strategies, providing online information retrieval, and preserving the information currently stored in the CRDO's information repository. Moreover, using the XTM technology, the system could get additional information from the farms through wireless communications, and so reducing the deployment costs.

Acknowledgements

This work was supported by the Instituto Nacional de Investigación y Tecnología Agraria y Agroalimentaria (INIA), Spain, under Grant PET2007-08-C11-06.

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