Tag-Based Browsing of Digital Collections with Inverted Indexes and Browsing Cache
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This document proposes a tag-based browsing system for digital collections that uses inverted indexes and a browsing cache to improve performance. Tags representing element-value pairs are used to filter resources. A browsing cache stores browsing states like filtered resources and selectable tags to speed up navigating when tag filters change. Preliminary experiments show the cache can substantially improve browsing speed over an uncached system using just inverted indexes, though with increased memory usage. Future work aims to integrate browsing automata and links between resources.
Tag-Based Browsing of Digital Collections with Inverted Indexes and Browsing Cache
- 1. Tag-Based Browsing of Digital Collections with Inverted Indexes and Browsing Cache Joaquín Gayoso-Cabada, Mercedes Gómez-Albarrán, José Luis Sierra Fac. Informática Universidad Complutense de Madrid
- 2. 2 Contents Introduction The Tag-Based Browsing Model Tag-Based Browsing with Inverted Indexes Adding a Browsing Cache Conclusions and Future Work
- 3. 3 Introduction Clavy: an experimental platform for learning object repositories with reconfiguable structures Clavy makes it possible to rearrange the hierarchical organization of elements in metadata schemata. These reconfigurations affect functionalities like learning object presentation, and browsing. In particular, although from a user’s point of view Clavy supports a guided browsing paradigm… … internally it supports more free and flexible browsing mechanisms… … able to take account of all the posible ways of browsing the repositories
- 4. 4 Introduction Clavy browsing is internally supported by a tag- based browsing system element – value pairs are abstracted as tags The browsing system maintains: – A set of active tags – The set of filtered objects – The set of additionally selectable tags, able to further shrink, but not to vanish, the filtered objects Updating the browsing snapshot when the set of active tags changes can be computationally- intensive To mitigate the cost we proposed a strategy based on inverted indexes and a browsing cache
- 5. 5 The Tag-Based Browsing Model Digital Collections Resources Tagging Resources Tagging r1 Cave-Painting Cantabrian Prehistoric r4 Tartesian Plateau Protohistoric r2 Cave-Painting Levant Prehistoric r5 Phoenician Penibaetic Protohistoric r3 Megalithic Cantabrian Prehistoric r6 Punic Levant Protohistoric Resources Content of Learning objects Tags Element-value pairs
- 6. 6 The Tag-Based Browsing Model Browsing Browsing state: – F Set of selected tags. – RF Set of filtered resources. – SF Set of selectable tags. Browsing actions: – +t Select the tag t. – xt Remove the tag t
- 7. 7 Browsing with Inverted Indexes Inverted Indexes For each tag t the inverted index returns the set of all the resources (t) tagged with t (Cave-Painting)={r1,r2} (Megalithic)={r3} (Tartesian)={r4} (Phoenician)={r5} (Punic)={r6} (Cantabrian)={r1,r3} (Levant)={r2,r6} (Plateau)={r4} (Penibaetic)={r5} (Prehistoric)={r1,r2,r3} (Protohistoric)={r4,r5,r6} Resources Tagging Resources Tagging r1 Cave-Painting Cantabrian Prehistoric r4 Tartesian Plateau Protohistoric r2 Cave-Painting Levant Prehistoric r5 Phoenician Penibaetic Protohistoric r3 Megalithic Cantabrian Prehistoric r6 Punic Levant Protohistoric Inverted index
- 8. 8 Browsing with Inverted Indexes The Browsing Strategy +t browsing action: – F F {t} – RF RF(t) – SF{t’SF-{t} | 0 < |RF(t’)| <|RF|} xt browsing action: – F F - {t} – RF t’F (t’) (or all the resources if F=) – SF{t’- F | 0 < |RF(t’)| <|RF|} F= is managed as a particular case: – RF – SF {t | |(t)| < ||}
- 9. 9 : filtered resource store F ⟶ RF : selectable tag store F ⟶ SF : representative store RF ⟶ F Adding a Browsing Cache CACHE#5 CACHE#4 CACHE#1 CACHE#2 ()= ()= CACHE#3 ()= (t10)=R1 F (t10,t1)=R2 F (R1 F )={t10} (R2 F )={t10,t1} ()= (t10)={t1,t2,t6,t7} (t10,t1)={t6,t7} ()= (t10)=R1 F (t10,t1)=R2 F (R1 F )={t10} (R2 F )={t10,t1} ()= (t10)={t1,t2,t6,t7} (t10,t1)={t6,t7} ()= (t10)=R1 F (t10,t1)=R2 F (R1 F )={t10} (R2 F )={t10,t1} ()= (t10)={t1,t2,t6,t7} (t10,t1)={t6,t7} ()= (t10)=R1 F (t10,t1)=R2 F (t1)=R5 F (R1 F )={t10} (R2 F )={t10,t1} ()= (t10)={t1,t2,t6,t7} (t10,t1)={t6,t7} (t1)={t6,t7} CACHE#6 ()= (t10)=R1 F (R1 F )={t10} ()= (t10)={t1,t2,t6,t7} +Prehistoric CACHE#1 +Cave-Painting CACHE#2 xCave-Painting CACHE#3 xPrehistoric CACHE#4+Cave-Painting CACHE#5 {Cave-Painting} {Cantabrian, Levant} {Prehistoric} {Cave-Painting, Megalithic, Cantabrian, Levant} {Prehistoric} {Cave-Painting, Megalithic, Cantabrian, Levant} R1 F =R0 F (t10) R2 F =R1 F (t1) R5 F =R4 F (t1) |R1 F (t1)|=2 |R1 F (t2)|=1 |R1 F (t3)|=0 |R1 F (t4)|=0 |R1 F (t5)|=0 |R1 F (t6)|=2 |R1 F (t7)|=1 |R1 F (t8)|=0 |R1 F (t9)|=0 |R1 F (t11)|=0 0<|R1 F (t)|<|R1 F | |R2 F (t2)|=0 |R2 F (t6)|=1 |R2 F (t7)|=1 | (t1)|=2 | (t2)|=1 | (t3)|=1 | (t4)|=1 | (t5)|=1 | (t6)|=2 | (t7)|=2 | (t8)|=1 | (t9)|=1 | (t10)|=3 | (t11)|=3 |(t)|< || {Prehistoric, Cave-Painting} {Cantabrian, Levant} 0<|R2 F (t)|<|R2 F | 345 {r1,r2,r3} {r1,r2} {r1,r2,r3}{r1,r2} 0 1 2 CACHE#6
- 10. 10 Conclusions A browsing strategy based on a suitable combination of inverted indexes and multilevel caches has been proposed to speed up the browsing process in Clavy Currently we are working on the empirical evaluation of our approach in Chasqui, a real-world repository in the Pre- Columbian American archeology field. Preliminary experiments suggest that the browsing cache can substantially speed up navigation with respect to a more basic, un-cached strategy (solely based on inverted indexes). The price to pay is the overhead generated by cache management, as well as the higher memory footprint caused by the technique. However, the experiments also make apparent how: (i) the cache management overhead is compensated by eliminating the explicit computation of the information associated to many browsing states, and (ii) the cache size is maintained within reasonable ranges, even when it is not upper-bounded.
- 11. 11 Future Work To improve the cache strategy by combining it with our previous work on navigation automata. To generalize the browsing strategy to support navigation through links among resources. To combine browsing and search, letting users browse search results according to the browsing model described.
- 12. Tag-Based Browsing of Digital Collections with Inverted Indexes and Browsing Cache Joaquín Gayoso-Cabada, Mercedes Gómez-Albarrán, José Luis Sierra Fac. Informática Universidad Complutense de Madrid